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The Linux Bootdisk HOWTO Graham Chapman, grahamc@zeta.org.au v1.02, 25 June 1995 This document describes how to create Linux boot, boot/root and util¡ ity maintenance disks. These disks could be used as rescue disks or to test new kernels. 1. Introduction 1.1. Why Build Boot Disks? Linux boot disks are useful in a number of situations, such as: ╖ Testing a new kernel. ╖ Recovering from disk or system failure. Such a failure could be anything from a lost boot sector to a disk head crash. There are several ways of producing boot disks: ╖ Use one from a distribution such as Slackware. This will at least allow you to boot. ╖ Use a rescue package to set up disks designed to be used as rescue disks. ╖ Learn what is required for each of the various types of disk to operate, then build your own. I originally chose the last option - learn how it works so that you can do it yourself. That way, if something breaks, you can work out what to do to fix it. Plus you learn a lot about how Linux works along the way. Once I understood how it all worked, then I changed to using the Bootkit rescue package to maintain my boot disks. Experienced Linux users may find little of use in this document. However users new to Linux system administration who wish to protect against root disk loss and other mishaps may find it useful. A note on versions - this document has been updated to support the following packages and versions: ╖ Linux 1.2.0 ╖ LILO 0.15 Copyright (c) Graham Chapman 1995. Permission is granted for this material to be freely used and distributed, provided the source is acknowledged. No warranty of any kind is provided. You use this material at your own risk. 1.2. Feedback and Credits I welcome any feedback, good or bad, on the content of this document. Please let me know if you find any errors or omissions. I thank the following people for correcting errors and providing useful suggestions for improvement: Randolph Bentson Grant R. Bowman Scott Burkett Bruce Elliot HARIGUCHI Youichi Bjxrn-Helge Mevik Dwight Spencer Cameron Spitzer Johannes Stille 1.3. Change History v1.02, 25 June 1995 ╖ Add: FAQ question on oversize ramdisk filesystems. ╖ Add: if using mkfs, use the -i option. ╖ Add: can use cp as well as dd to copy to raw disk. ╖ Chg: correct explanation of /dev/fd0 vs /dev/fd0H1440. ╖ Chg: use "zImage" terminology to conform to standard usage. ╖ Add: mke2fs -m 0 will provide more usable disk space. ╖ Add: re-run LILO if the kernel has changed. ╖ Add: move rescue packages to new section under "References". ╖ Add: new rescue packages Bootkit and CatRescue. ╖ Add: FAQ question on cannot execute errors. ╖ Add: shell scripts are samples only - I now use Bootkit. ╖ Chg: stop using < and > in command examples - too confusing. ╖ Chg: sample directory listings are now of diskettes, not model. ╖ Chg: use more consistent terminology with ramdisks. v1.01, 6 February 1995 ╖ Fix: DO NOT cp kernel_filename /dev/fd0 - this will overwrite any file system on the diskette. ╖ Fix: Put LILO boot.b and map files on target disk. ╖ Add: -dp flags to cp commands to avoid problems. ╖ Chg: restructure to try to improve readability. ╖ Add: can now use ext2 filesystem on root diskettes. ╖ Chg: can now separate boot and root diskettes. ╖ Add: credits section in Introduction. ╖ Add: FAQ. v1.0, 2 January 1995 ╖ Converted to conform to HOWTO documentation standards. ╖ Added new section - Change History. ╖ Various minor corrections. v0.10, 1 November 1994 Original version, labelled "draft". 2. Disks 2.1. Summary of Disk Types I classify boot-related disks into 4 types. The discussion here and throughout this document uses the term "disk" to refer to diskettes unless otherwise specified. Most of the discussion could be equally well applied to hard disks. A summary of disk types and uses is: boot A disk containing a kernel which can be booted. The disk can contain a filesystem and use a boot loader to boot, or it can simply contain the kernel only at the start of the disk. The disk can be used to boot the kernel using a root file system on another disk. This could be useful if you lost your boot loader due to, for example, an incorrect installation attempt. root A disk with a file system containing everything required to run a Linux system. It does not necessarily contain either a kernel or a boot loader. This disk can be used to run the system independently of any other disks, once the kernel has been booted. A special kernel feature allows a separate root disk to be mounted after booting, with the root disk being automatically copied to a ramdisk. You could use this type of disk to check another disk for corruption without mounting it, or to restore another disk after a disk failure or loss of files. boot/root A disk which is the same as a root disk, but contains a kernel and a boot loader. It can be used to boot from, and to run the system. The advantage of this type of disk is that is it compact - everything required is on a single disk. However the gradually increasing size of everything means that it won't necessarily always be possbile to fit everything on a single diskette. utility A disk which contains a file system, but is not intended to be mounted as a root file system. It is an additional data disk. You would use this type of disk to carry additional utilities where you have too much to fit on your root disk. The term "utility" only really applies to diskettes, where you would use a utility disk to store additional recovery utility software. 2.2. Boot 2.2.1. Overview All PC systems start the boot process by executing code in ROM to load the sector from sector 0, cylinder 0 of the boot drive and try and execute it. On most bootable disks, sector 0, cylinder 0 contains either: ╖ code from a boot loader such as LILO, which locates the kernel, loads it and executes it to start the boot proper. ╖ the start of an operating system kernel, such as Linux. If a Linux kernel has been written to a diskette as a raw device, then the first sector will be the first sector of the Linux kernel itself, and this sector will continue the boot process by loading the rest of the kernel and running Linux. For a more detailed description of the boot sector contents, see the documentation in lilo-01.5 or higher. An alternative method of storing a kernel on a boot disk is to create a filesystem, not as a root filesystem, but simply as a means of installing LILO and thus allowing boot-time command line options to be specified. For example, the same kernel could then be used to boot using a hard disk root filesystem, or a diskette root filesystem. This could be useful if you were trying to rebuild the hard disk filesystem, and wanted to repeatedly test results. 2.2.2. Setting Pointer to Root The kernel must somehow obtain a pointer to the drive and partititon to be mounted as the root drive. This can be provided in several ways: ╖ By setting ROOT_DEV = devicename in the Linux kernel makefile and rebuilding the kernel (for advice on how to rebuild the kernel, read the Linux FAQ and look in /usr/src/linux). Comments in the Linux makefile describe the valid values for devicename. ╖ By running the rdev utility: rdev filename devicename This will set the root device of the kernel contained in filename to be devicename. For example: rdev zImage /dev/sda1 This sets the root device in the kernel in zImage to the first parti¡ tion on the first SCSI drive. There are some alternative ways of issuing the rdev command. Try: rdev -h and it will display command usage. There is usually no need to configure the root device for boot diskette use, because the kernel currently used to boot from probably already points to the root drive device. The need can arise, howoever, if you obtain a kernel from another machine, for example, from a distribution, or if you want to use the kernel to boot a root diskette. It is probably a good idea to check the current root drive setting, just in case it is wrong. To get rdev to check the current root device in a kernel file, enter the command: rdev <filename> It is possible to change the root device set in a kernel by means other than using rdev. For details, see the FAQ at the end of this document. 2.2.3. Copying Kernel to Boot Diskette Once the kernel has been configured then it must be copied to the boot diskette. The commands described below (and throughout the HOWTO) assume that the diskettes have been formatted. If not, then use fdformat to format the diskettes before continuing. If the disk is not intended to contain a file system, then the kernel can be copied using the dd command, as follows: dd if=infilename of=devicename where infilename is the name of the kernel and devicename is the diskette raw device, usually /dev/fd0 The cp command can also be used: cp filename devicename For example: dd if=zImage of=/dev/fd0 or cp zImage /dev/fd0 The seek parameter to the dd command should NOT be used. The file must be copied to start at the boot sector (sector 0, cylinder 0), and omitting the seek parameter will do this. The output device name to be used is usually /dev/fd0 for the primary diskette drive (i.e. drive "A:" in DOS), and /dev/fd1 for the secondary. These device names will cause the kernel to autodetect the attributes of the drives. Drive attributes can be specified to the kernel by using other device names: for example /dev/fd0H1440 specifies a high density 1.44 Mb drive. It is rare to need to use these specific device names. Where the kernel is to be copied to a boot disk containing a filesystem, then the disk is mounted at a suitable point in a currently-mounted filesystem, then the cp command is used. For example: mount -t ext2 /dev/fd0 /mnt cp zImage /mnt umount /mnt Note that for almost all operations in this HOWTO, the user should be operating as the superuser. 2.3. Root 2.3.1. Overview A root disk contains a complete working Linux system, but without necessarily including a kernel. In other words, the disk may not be bootable, but once the kernel is running, the root disk contains everything needed to support a full Linux system. To be able to do this, the disk must include the minimum requirements for a Linux system: ╖ File system. ╖ Minimum set of directories - dev, proc, bin, etc, lib, usr, tmp. ╖ Basic set of utilities - bash (to run a shell), ls, cp etc. ╖ Minimum set of config files - rc, inittab, fstab etc. ╖ Runtime library to provide basic functions used by utilities. Of course, any system only becomes useful when you can run something on it, and a root diskette usually only becomes useful when you can do something like: ╖ Check a file system on another drive, for example to check your root file system on your hard drive, you need to be able to boot Linux from another drive, as you can with a root diskette system. Then you can run fsck on your original root drive while it is not mounted. ╖ Restore all or part of your original root drive from backup using archive/compression utilities including cpio, tar, gzip and ftape. 2.4. Boot/Root This is essentially the same as the root disk, with the addition of a kernel and a boot loader such as LILO. With this configuration, a kernel file is copied to the root file system, and LILO is then run to install a configuration which points to the kernel file on the target disk. At boot time, LILO will boot the kernel from the target disk. Several files must be copied to the diskette for this method to work. Details of these files and the required LILO configuration, including a working sample, are given below in the section titled "LILO". 2.4.1. RAM Disks and Root Filesystems on Diskette For a diskette root filesystem to be efficient, you need to be able to run it from a ramdisk, i.e. an emulated disk drive in main memory. This avoids having the system run at a snail's pace, which a diskette would impose. The Ftape HOWTO states that a ramdisk will be required when using Ftape because Ftape requires exclusive use of the diskette controller. There is an added benefit from using a ramdisk - the Linux kernel includes an automatic ramdisk root feature, whereby it will, under certain circumstances, automatically copy the contents of a root diskette to a ramdisk, and then switch the root drive to be the ramdisk instead of the diskette. This has two major benefits: ╖ The system runs a lot faster. ╖ The diskette drive is freed up to allow other diskettes to be used on a single-diskette drive system. The requirements for this feature to be invoked are: ╖ The file system on the diskette drive must be either a minix or an ext2 file system. The ext2 file system is generally the preferred file system to use. Note that if you have a Linux kernel earlier than 1.1.73, then you should see the comments in the section titled "File Systems" to see whether your kernel will support ext2. If your kernel is old then you may have to use minix. This will not cause any significant problems. ╖ A ramdisk must be configured into the kernel, and it must be at least as big as the diskette drive. A ramdisk can be configured into the kernel in several ways: ╖ By uncommenting the RAMDISK macro in the Linux kernel makefile, so that it reads: RAMDISK = -DRAMDISK=1440 to define a ramdisk of 1440 1K blocks, the size of a high-density diskette. ╖ By running the rdev utility, available on most Linux systems. This utility displays or sets values for several things in the kernel, including the desired size for a ramdisk. To configure a ramdisk of 1440 blocks into a kernel in a file named zImage, enter: rdev -r zImage 1440 this might change in the future, of course. To see what your version of rdev does, enter the command: rdev -h and it should display its options. ╖ By using the boot loader package LILO to configure it into your kernel at boot time. This can be done using the LILO configuration parameter: ramdisk = 1440 to request a ramdisk of 1440 1K blocks at boot time. ╖ By interrupting a LILO automatic boot and adding ramdisk=1440 to the command line. For example, such a command line might be: zImage ramdisk=1440 See the section on LILO for more details. ╖ By editing the kernel file and altering the values near the start of the file which record the ramdisk size. This is definitely a last resort, but can be done. See the FAQ near the end of this document for more details. The easiest of these methods is LILO configuration, because you need to set up a LILO configuration file anyway, so why not add the ramdisk size here? LILO configuration is briefly described in a section titled "LILO" below, but it is advisable to obtain the latest stable version of LILO from your nearest Linux mirror site, and read the documentation that comes with it. Ramdisks can be made larger than the size of a diskette, and made to contain a filesystem as large as the ramdisk. This can be useful to load all the software required for rescue work onto a single high- performance ramdisk. The method of doing this is described in the FAQ section under the question "How can I create an oversize ramdisk filesystem?" 2.5. Utility Often one disk is not sufficient to hold all the software you need to be able to perform rescue functions of analysing, repairing and restoring corrupted disk drives. By the time you include tar, gzip e2fsck, fdisk, Ftape and so on, there is enough for a whole new diskette, maybe even more if you want lots of tools. This means that a rescue set often requires a utility diskette, with a file system containing any extra files required. This file system can then be mounted at a convenient point, such as /usr, on the boot/root system. Creating a file system is fairly easy, and is described in the section titled "File Systems". 3. Components 3.1. File Systems The Linux kernel now supports two file system types for root disks to be automatically copied to ramdisk. These are minix and ext2, of which ext2 is the preferred file system. The ext2 support was added sometime between 1.1.17 and 1.1.57, I'm not sure exactly which. If you have a kernel within this range then edit /usr/src/linux/drivers/block/ramdisk.c and look for the word "ext2". If it is not found, then you will have to use a minix file system, and therefore the "mkfs" command to create it. (If using mkfs, use the -i option to specify more inodes than the default; -i 2000 is suggested). To create an ext2 file system on a diskette on my system, I issue the following command: mke2fs -m 0 /dev/fd0 The mke2fs command will automatically detect the space available and configure itself accordingly. If desired, the diskette size in 1Kb blocks can be specified to speed up mke2fs operation. The -m 0 parameter prevents it from reserving space for root, and hence provides more usable space on the disk. An easy way to test the result is to create a system using the above command or similar, and then attempt to mount the diskette. If it is an ext2 system, then the command: mount -t ext2 /dev/fd0 /<mount point> should work. 3.2. Kernel 3.2.1. Building a Custom Kernel In most cases it would be possible to copy your current kernel and boot the diskette from that. However there may be cases where you wish to build a separate one. One reason is size. The kernel is one of the largest files in a minimum system, so if you want to build a boot/root diskette, then you will have to reduce the size of the kernel as much as possible. The kernel now supports changing the diskette after booting and before mounting root, so it is not necessary any more to squeeze the kernel into the same disk as everything else, therefore these comments apply only if you choose to build a boot/root diskette. There are two ways of reducing kernel size: ╖ Building it with the minumum set of facilities necessary to support the desired system. This means leaving out everything you don't need. Networking is a good thing to leave out, as well as support for any disk drives and other devices which you don't need when running your boot/root system. ╖ Compressing it, using the standard compressed-kernel option included in the makefile: make zImage Refer to the documentation included with the kernel source for up-to- date information on building compressed kernels. Note that the kernel source is usually in /usr/src/linux. Having worked out a minimum set of facilities to include in a kernel, you then need to work out what to add back in. Probably the most common uses for a boot/root diskette system would be to examine and restore a corrupted root file system, and to do this you may need kernel support. For example, if your backups are all held on tape using Ftape to access your tape drive, then, if you lose your current root drive and drives containing Ftape, then you will not be able to restore from your backup tapes. You will have to reinstall Linux, download and reinstall Ftape, and then try and read your backups. It is probably desirable to maintain a copy of the same version of backup utilities used to write the backups, so that you don't waste time trying to install versions that cannot read your backup tapes. The point here is that, whatever I/O support you have added to your kernel to support backups should also be added into your boot/root kernel. The procedure for actually building the kernel is described in the documentation that comes with the kernel. It is quite easy to follow, so start by looking in /usr/src/linux. Note that if you have trouble building a kernel, then you should probably not attempt to build boot/root systems anyway. 3.3. Devices A /dev directory containing a special file for all devices to be used by the system is mandatory for any Linux system. The directory itself is a normal directory, and can be created with the mkdir command in the normal way. The device special files, however, must be created in a special way, using the mknod command. There is a shortcut, though - copy your existing /dev directory contents, and delete the ones you don't want. The only requirement is that you copy the device special files using the -R option. This will copy the directory without attempting to copy the contents of the files. Note that if you use lower caser, as in "-r", there will be a vast difference, because you will probably end up copying the entire contents of all of your hard disks - or at least as much of them as will fit on a diskette! Therefore, take care, and use the command: cp -dpR /dev /mnt assuming that the diskette is mounted at /mnt. The dp switches ensure that symbolic links are copied as links (rather than the target file being copied) and that the original file attributes are preserved, thus preserving ownership information. If you want to do it the hard way, use ls -l to display the major and minor device numbers for the devices you want, and create them on the diskette using mknod. Many distributions include a shell script called MAKEDEV in the /dev directory. This shell script could be used to create the devices, but it is probably easier to just copy your existing ones, especially for rescue disk purposes. Whichever way the device directory is copied, it is worth checking that any special devices you need have been placed on the rescue diskette. For example, Ftape uses tape devices, so you will need to copy all of these. 3.4. Directories It might be possible to get away with just /dev, /proc and /etc to run a Linux system. I don't know - I've never tested it. However a reasonable minimum set of directories consists of the following: /dev Required to perform I/O with devices /proc Required by the ps command /etc System configuration files /bin Utility executables considered part of the system /lib Shared libraries to provide run-time support /mnt A mount point for maintenance on other disks /usr Additional utilities and applications Note that the directory tree presented here is for root diskette use only. Refer to the Linux File System Standard for much better information on how file systems should be structured in "standard" Linux systems. Four of these directories can be created very easily: ╖ /dev is described above in the section titled DEVICES. ╖ /proc only needs to exist. Once the directory is created using mkdir, nothing more is required. ╖ Of the others, /mnt and /usr are included in this list only as mount points for use after the boot/root system is running. Hence again, these directories only need to be created. The remaining 3 directories are described in the following sections. 3.4.1. /etc This directory must contain a number of configuration files. On most systems, these can be divided into 3 groups: ╖ Required at all times, e.g. rc, fstab, passwd. ╖ May be required, but no-one is too sure. ╖ Junk that crept in. Files which are not essential can be identified with the command: ls -ltru This lists files in reverse order of date last accessed, so if any files are not being accessed, then they can be omitted from a root diskette. On my root diskettes, I have the number of config files down to 15. This reduces my work to dealing with three sets of files: ╖ The ones I must configure for a boot/root system: rc system startup script fstab list of file systems to be mounted inittab parameters for the init process - the first process started at boot time. ╖ the ones I should tidy up for a boot/root system: passwd list of logins shadow contains passwords These should be pruned on secure systems to avoid copying user's pass¡ words off the system, and so that when you boot from diskette, unwanted logins are rejected. ╖ The rest. They work at the moment, so I leave them alone. Out of this, I only really have to configure two files, and what they should contain is suprisingly small. ╖ rc should contain: #!/bin/sh /etc/mount -av /bin/hostname boot_root and I don't really need to run hostname - it just looks nicer if I do. Even mount is actually only needed to mount /proc to support the ps command - Linux will run without it. ╖ fstab should contain: /dev/fd0 / ext2 defaults /proc /proc proc defaults I don't think that the first entry is really needed, but I find that if I leave it out, mount won't mount /proc. Inittab should be ok as is, unless you want to ensure that users on serial ports cannot login. To prevent this, comment out all the entries for /etc/getty which include a ttys or ttyS device at the end of the line. Leave in the tty ports so that you can login at the console. Inittab defines what the system will run or rerun in various states including startup, move to multi-user mode, powerfail, and others. A point to be careful of here is to carefully check that the commands entered in inittab refer to programs which are present and to the correct directory. If you place your command files on your rescue disk using the sample directory listing in this HOWTO as a guide, and then copy your inittab to your rescue disk without checking it, then the probability of failure will be quite high, because half of the inittab entries will refer to missing programs or to the wrong directory. It is worth noting here as well that some programs cannot be moved from one directory to another or they will fail at runtime because they have hardcoded the name of another program which they attempt to run. For example on my system, /etc/shutdown has hardcoded in it /etc/reboot. If I move reboot to /bin/reboot, and then issue a shutdown command, it will fail because it can't find the reboot file. For the rest, just copy all the text files in your /etc directory, plus all the executables in your /etc directory that you cannot be sure you do not need. As a guide, consult the sample ls listing in "Sample Boot/Root ls-lR Directory Listing" - this is what I have, so probably it will be sufficient for you if you copy only those files. In practice, a single rc file is restrictive; most systems now use an /etc/rc.d directory containing shell scripts for different run levels. The absolute minimum is a single rc script, but it will probably be a lot simpler in practice to copy the inittab and /etc/rc.d directory from your existing system, and prune the shell scripts in the rc.d directory to remove processing not relevent to a diskette system environment. 3.4.2. /bin Here is a convenient point to place the extra utilities you need to perform basic operations, utilities such as ls, mv, cat, dd etc. See the section titled "Sample Boot/Root ls-lR Directory Listing" for the list of files that I place in my boot/root /bin directory. You may notice that it does not include any of the utilities required to restore from backup, such as cpio, tar, gzip etc. That is because I place these on a separate utility diskette, to save space on the boot/root diskette. Once I have booted my boot/root diskette, it then copies itself to the ramdisk leaving the diskette drive free to mount another diskette, the utility diskette. I usually mount this as /usr. Creation of a utility diskette is described below in the section titled "Adding Utility Diskettes". 3.4.3. /lib Two libraries are required to run many facilities under Linux: ╖ ld.so ╖ libc.so.4 If they are not found in your /lib directory then the system will be unable to boot. If you're lucky you may see an error message telling you why. These should be present in you existing /lib directory. Note that libc.so.4 may be a symlink to a libc library with version number in the filename. If you issue the command: ls -l /lib you will see something like: libc.so.4 -> libc.so.4.5.21 In this case, the libc library you want is libc.so.4.5.21. 3.5. LILO 3.5.1. Overview For the boot/root to be any use, it must be bootable. To achieve this, the easiest way is to install a boot loader, which is a piece of executable code stored at sector 0, cylinder 0 of the diskette. See the section above titled "BOOT DISKETTE" for an overview of the boot process. LILO is a tried and trusted boot loader available from any Linux mirror site. It allows you to configure the boot loader, including: ╖ Which device is to be mounted as the root drive. ╖ Whether to use a ramdisk. 3.5.2. Sample LILO Configuration This provides a very convenient place to specify to the kernel how it should boot. My root/boot LILO configuration file, used with LILO 0.15, is: ______________________________________________________________________ boot = /dev/fd0 install = ./mnt/boot.b map = ./mnt/lilo.map delay = 50 message = ./mnt/lilo.msg timeout = 150 compact image = ./mnt/zImage ramdisk = 1440 root = /dev/fd0 ______________________________________________________________________ Note that boot.b, lilo.msg and the kernel must first have been copied to the diskette using a command similar to: ______________________________________________________________________ cp /boot/boot.b ./mnt ______________________________________________________________________ If this is not done, then LILO will not run correctly at boot time if the hard disk is not available, and there is little point setting up a rescue disk which requires a hard disk in order to boot. I run lilo using the command: /sbin/lilo -C <configfile> I run it from the directory containing the mnt directory where I have mounted the diskette. This means that I am telling LILO to install a boot loader on the boot device (/dev/fd0 in this case), to boot a kernel in the root directory of the diskette. I have also specified that I want the root device to be the diskette, and I want a ramdisk created of 1440 1K blocks, the same size as the diskette. Since I have created an ext2 file system on the diskette, this completes all the conditions required for Linux to automatically switch the root device to the ramdisk, and copy the diskette contents there as well. The ramdisk features of Linux are described further in the section above titled "RAM DISKS AND BOOT/ROOT SYSTEMS". It is also worth considering using the "single" parameter to cause Linux to boot in single-user mode. This could be useful to prevent users logging in on serial ports. I also use the "DELAY" "MESSAGE" and "TIMEOUT" statements so that when I boot the disk, LILO will give me the opportunity to enter command line options if I wish. I don't need them at present, but I never know when I might want to set a different root device or mount a filesystem read-only. The message file I use contains the message: Linux Boot/Root Diskette ======================== Enter a command line of the form: zImage [ command-line options] If nothing is entered, linux will be loaded with defaults after 15 seconds. This is simply a reminder to myself what my choices are. Readers are urged to read the LILO documentation carefully before atttempting to install anything. It is relatively easy to destroy partitions if you use the wrong "boot = " parameter. If you are inexperienced, do NOT run LILO until you are sure you understand it and you have triple-checked your parameters. Note that you must re-run LILO every time you change the kernel, so that LILO can set up its map file to correctly describe the new kernel file. It is in fact possible to replace the kernel file with one which is almost identical without rerunning LILO, but it is far better not to gamble - if you change the kernel, re-run LILO. 3.5.3. Removing LILO One other thing I might as well add here while I'm on the LILO topic: if you mess up lilo on a drive containing DOS, you can always replace the boot sector with the DOS boot loader by issuing the DOS command: FDISK /MBR where MBR stands for "Master Boot Record". Note that some purists disagree with this, and they may have grounds, but it works. 3.5.4. Useful LILO Options LILO has several useful options which are worth keeping in mind when building boot disks: ╖ Command line options - you can enter command line options to set the root device, ramdisk size, special device parameters, or other things. If you include the DELAY = nn statement in your LILO configuration file, then LILO will pause to allow you to select a kernel image to boot, and to enter, on the same line, any options. For example: zImage aha152x=0x340,11,3,1 ro will pass the aha152x parameters through to the aha152x scsi disk driver (provided that driver has been included when the kernel was built) and will ask for the root filesystem to be mounted read-only. ╖ Command line "lock" option - this option asks LILO to store the command line entered as the default command line to be used for all future boots. This is particularly useful where you have a device which cannot be autoselected. By using "lock" you can avoid having to type in the device parameter string every time you boot. For example: zImage aha152x=0x340,11,3,1 root=/dev/sda8 ro lock ╖ APPEND configuration statement - this allows device parameter strings to be stored in the configuration, as an alternative to using the "lock" command line option. Note that any keywords of the form word=value MUST be enclosed in quotes. For example: APPEND = "aha152x=0x340,11,3,1" ╖ DELAY configuration statement - this pauses for DELAY tenths of seconds and allows the user to interrupt the automatic boot of the default command line, so that the user can enter an alternate command line. 4. Samples 4.1. Disk Directory Listings This lists the contents of directories from my root and utility diskettes. These lists are provided as an example only of the files included to create a working system. The disks were created using the Bootkit package, which copies to diskette only those files that you want copied. 4.1.1. Root Disk ls-lR Directory Listing The root listing is of a diskette mounted at /mnt. total 27 drwx------ 2 root root 1024 Jun 11 23:23 bin/ drwxr-xr-x 2 root root 3072 Jun 11 23:24 dev/ drwxr-xr-x 3 root root 1024 May 30 06:38 etc/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 home/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 lib/ drwxr-xr-x 2 root root 12288 Jun 11 23:23 lost+found/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 mnt/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 proc/ drwxr-xr-x 2 root root 1024 May 30 05:56 root/ drwxr-xr-x 2 root root 1024 Jun 3 23:39 sbin/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 tmp/ drwxr-xr-x 3 root root 1024 May 30 05:48 usr/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 util/ drwxr-xr-x 5 root root 1024 May 30 05:58 var/ /mnt/bin: total 664 -rwxr-xr-x 1 root root 222208 Sep 7 1992 bash* -rwxr-xr-x 1 root other 4376 Sep 8 1992 cat* -rwxr-xr-x 1 root other 5088 Sep 4 1992 chmod* -rwxr-xr-x 1 root other 4024 Sep 4 1992 chown* -rwxr-xr-x 1 root other 12104 Sep 4 1992 cp* -rwxr-xr-x 1 root other 4376 Sep 5 1992 cut* -rwxr-xr-x 1 root other 7592 Sep 4 1992 dd* -rwxr-xr-x 1 root other 4656 Sep 4 1992 df* -rwxr-xr-x 1 root root 37892 May 5 1994 e2fsck* -rwx--x--x 1 root root 14396 Sep 20 1992 fdisk* -r-x--x--x 1 bin bin 3536 Feb 19 19:14 hostname* -rwxr-xr-x 1 root other 5292 Sep 4 1992 ln* -rws--x--x 1 root root 24352 Jan 16 1993 login* -rwxr-xr-x 1 root other 4104 Sep 4 1992 mkdir* -rwxr-xr-x 1 root root 21508 May 5 1994 mke2fs* -rwxr-xr-x 1 root other 3336 Sep 4 1992 mknod* -rwx--x--x 1 root root 2432 Sep 20 1992 mkswap* -rwxr-xr-x 1 root root 9596 Jun 10 22:12 mount* -rwxr-xr-x 1 root other 6724 Sep 4 1992 mv* -rwxr-xr-x 1 root root 11132 Apr 10 1993 ps* -rwxr-xr-x 1 root other 5056 Sep 4 1992 rm* -rwxr-xr-x 1 root root 222208 Sep 7 1992 sh* -rws--x--x 1 root root 16464 Jan 16 1993 su* -rwxr-xr-x 1 root root 1204 Sep 17 1992 sync* -rwxr-xr-x 1 root root 6188 Apr 17 1993 umount* /mnt/dev: total 72 -rwxr-xr-x 1 root root 8331 Mar 14 1993 MAKEDEV* lrwxrwxrwx 1 root root 4 Jun 11 23:24 console -> tty0 crw-rw-rw- 1 root tty 5, 64 Apr 1 1993 cua0 crw-rw-rw- 1 root tty 5, 65 Mar 19 19:35 cua1 crw-rw-rw- 1 root tty 5, 66 Apr 10 1993 cua2 crw-rw-rw- 1 root tty 5, 67 Apr 10 1993 cua3 brw-r--r-- 1 root root 2, 0 Aug 29 1992 fd0 brw-r--r-- 1 root root 2, 12 Aug 29 1992 fd0D360 brw-r--r-- 1 root root 2, 16 Aug 29 1992 fd0D720 brw-r--r-- 1 root root 2, 28 Aug 29 1992 fd0H1440 brw-r--r-- 1 root root 2, 12 Aug 29 1992 fd0H360 brw-r--r-- 1 root root 2, 16 Aug 29 1992 fd0H720 brw-r--r-- 1 root root 2, 4 Aug 29 1992 fd0d360 brw-r--r-- 1 root root 2, 8 Jan 15 1993 fd0h1200 brw-r--r-- 1 root root 2, 20 Aug 29 1992 fd0h360 brw-r--r-- 1 root root 2, 24 Aug 29 1992 fd0h720 brw-r--r-- 1 root root 2, 1 Aug 29 1992 fd1 brw-r--r-- 1 root root 2, 13 Aug 29 1992 fd1D360 brw-r--r-- 1 root root 2, 17 Aug 29 1992 fd1D720 brw-r--r-- 1 root root 2, 29 Aug 29 1992 fd1H1440 brw-r--r-- 1 root root 2, 13 Aug 29 1992 fd1H360 brw-r--r-- 1 root root 2, 17 Aug 29 1992 fd1H720 brw-r--r-- 1 root root 2, 5 Aug 29 1992 fd1d360 brw-r--r-- 1 root root 2, 9 Aug 29 1992 fd1h1200 brw-r--r-- 1 root root 2, 21 Aug 29 1992 fd1h360 brw-r--r-- 1 root root 2, 25 Aug 29 1992 fd1h720 brw-r----- 1 root root 3, 0 Aug 29 1992 hda brw-r----- 1 root root 3, 1 Aug 29 1992 hda1 brw-r----- 1 root root 3, 2 Aug 29 1992 hda2 brw-r----- 1 root root 3, 3 Aug 29 1992 hda3 brw-r----- 1 root root 3, 4 Aug 29 1992 hda4 brw-r----- 1 root root 3, 5 Aug 29 1992 hda5 brw-r----- 1 root root 3, 6 Aug 29 1992 hda6 brw-r----- 1 root root 3, 7 Aug 29 1992 hda7 brw-r----- 1 root root 3, 8 Aug 29 1992 hda8 brw-r----- 1 root root 3, 64 Aug 29 1992 hdb brw-r----- 1 root root 3, 65 Aug 29 1992 hdb1 brw-r----- 1 root root 3, 66 Aug 29 1992 hdb2 brw-r----- 1 root root 3, 67 Aug 29 1992 hdb3 brw-r----- 1 root root 3, 68 Aug 29 1992 hdb4 brw-r----- 1 root root 3, 69 Aug 29 1992 hdb5 brw-r----- 1 root root 3, 70 Aug 29 1992 hdb6 brw-r----- 1 root root 3, 71 Aug 29 1992 hdb7 brw-r----- 1 root root 3, 72 Aug 29 1992 hdb8 crw-r----- 1 root kmem 1, 2 Aug 29 1992 kmem crw-rw-rw- 1 root root 6, 0 Aug 29 1992 lp0 crw-rw-rw- 1 root root 6, 1 Aug 29 1992 lp1 crw-rw-rw- 1 root root 6, 2 Aug 29 1992 lp2 crw-r----- 1 root sys 1, 1 Aug 29 1992 mem lrwxrwxrwx 1 root root 4 Jun 11 23:24 mouse -> cua1 crw-rw-rw- 1 root root 27, 4 Jul 31 1994 nrft0 crw-rw-rw- 1 root root 27, 5 Jul 31 1994 nrft1 crw-rw-rw- 1 root root 27, 6 Jul 31 1994 nrft2 crw-rw-rw- 1 root root 27, 7 Jul 31 1994 nrft3 crw------- 1 root root 9, 128 Jan 23 1993 nrmt0 crw-rw-rw- 1 root root 1, 3 Aug 29 1992 null crw-r----- 1 root root 6, 0 Aug 29 1992 par0 crw-r----- 1 root root 6, 1 Aug 29 1992 par1 crw-r----- 1 root root 6, 2 Aug 29 1992 par2 crw-r----- 1 root root 1, 4 Aug 29 1992 port crw-rw-rw- 1 root root 4, 128 Jun 10 00:10 ptyp0 crw-rw-rw- 1 root root 4, 129 Apr 10 14:51 ptyp1 crw-rw-rw- 1 root root 4, 130 Aug 21 1994 ptyp2 crw-rw-rw- 1 root root 4, 131 Apr 12 1993 ptyp3 crw-rw-rw- 1 root tty 4, 132 Jan 3 1993 ptyp4 crw-rw-rw- 1 root tty 4, 133 Jan 3 1993 ptyp5 crw-rw-rw- 1 root tty 4, 134 Jan 3 1993 ptyp6 crw-rw-rw- 1 root tty 4, 135 Jan 3 1993 ptyp7 crw-rw-rw- 1 root tty 4, 136 Jan 3 1993 ptyp8 crw-rw-rw- 1 root tty 4, 137 Jan 3 1993 ptyp9 crw-rw-rw- 1 root tty 4, 138 Jan 3 1993 ptypa crw-rw-rw- 1 root tty 4, 139 Jan 3 1993 ptypb crw-rw-rw- 1 root tty 4, 140 Jan 3 1993 ptypc crw-rw-rw- 1 root tty 4, 141 Jan 3 1993 ptypd crw-rw-rw- 1 root tty 4, 142 Jan 3 1993 ptype crw-rw-rw- 1 root tty 4, 143 Jan 3 1993 ptypf brw-rw---- 1 root root 1, 0 Jun 8 18:49 ram crw-rw-rw- 1 root root 27, 0 Jul 31 1994 rft0 crw-rw-rw- 1 root root 27, 1 Jul 31 1994 rft1 crw-rw-rw- 1 root root 27, 2 Jul 31 1994 rft2 crw-rw-rw- 1 root root 27, 3 Jul 31 1994 rft3 crw------- 1 root root 9, 0 Jan 23 1993 rmt0 brw-r----- 1 root root 8, 0 Aug 29 1992 sda brw-r----- 1 root root 8, 1 Aug 29 1992 sda1 brw-r----- 1 root root 8, 2 Aug 29 1992 sda2 brw-r----- 1 root root 8, 3 Aug 29 1992 sda3 brw-r----- 1 root root 8, 4 Aug 29 1992 sda4 brw-r----- 1 root root 8, 5 Aug 29 1992 sda5 brw-r----- 1 root root 8, 6 Aug 29 1992 sda6 brw-r----- 1 root root 8, 7 Aug 29 1992 sda7 brw-r----- 1 root root 8, 8 Aug 29 1992 sda8 brw-r----- 1 root root 8, 16 Aug 29 1992 sdb brw-r----- 1 root root 8, 17 Aug 29 1992 sdb1 brw-r----- 1 root root 8, 18 Aug 29 1992 sdb2 brw-r----- 1 root root 8, 19 Aug 29 1992 sdb3 brw-r----- 1 root root 8, 20 Aug 29 1992 sdb4 brw-r----- 1 root root 8, 21 Aug 29 1992 sdb5 brw-r----- 1 root root 8, 22 Aug 29 1992 sdb6 brw-r----- 1 root root 8, 23 Aug 29 1992 sdb7 brw-r----- 1 root root 8, 24 Aug 29 1992 sdb8 brw------- 1 bin bin 8, 32 Jun 30 1992 sdc brw------- 1 bin bin 8, 33 Jun 30 1992 sdc1 brw------- 1 bin bin 8, 34 Jun 30 1992 sdc2 brw------- 1 bin bin 8, 35 Jun 30 1992 sdc3 brw------- 1 bin bin 8, 36 Jun 30 1992 sdc4 brw------- 1 bin bin 8, 37 Jun 30 1992 sdc5 brw------- 1 bin bin 8, 38 Jun 30 1992 sdc6 brw------- 1 bin bin 8, 39 Jun 30 1992 sdc7 brw------- 1 bin bin 8, 40 Jun 30 1992 sdc8 brw------- 1 bin bin 8, 48 Jun 30 1992 sdd brw------- 1 bin bin 8, 49 Jun 30 1992 sdd1 brw------- 1 bin bin 8, 50 Jun 30 1992 sdd2 brw------- 1 bin bin 8, 51 Jun 30 1992 sdd3 brw------- 1 bin bin 8, 52 Jun 30 1992 sdd4 brw------- 1 bin bin 8, 53 Jun 30 1992 sdd5 brw------- 1 bin bin 8, 54 Jun 30 1992 sdd6 brw------- 1 bin bin 8, 55 Jun 30 1992 sdd7 brw------- 1 bin bin 8, 56 Jun 30 1992 sdd8 brw------- 1 bin bin 8, 64 Jun 30 1992 sde brw------- 1 bin bin 8, 65 Jun 30 1992 sde1 brw------- 1 bin bin 8, 66 Jun 30 1992 sde2 brw------- 1 bin bin 8, 67 Jun 30 1992 sde3 brw------- 1 bin bin 8, 68 Jun 30 1992 sde4 brw------- 1 bin bin 8, 69 Jun 30 1992 sde5 brw------- 1 bin bin 8, 70 Jun 30 1992 sde6 brw------- 1 bin bin 8, 71 Jun 30 1992 sde7 brw------- 1 bin bin 8, 72 Jun 30 1992 sde8 crw-rw-rw- 1 root root 5, 0 Apr 16 1994 tty crw-rw-rw- 1 grahamc other 4, 0 Jun 11 23:21 tty0 crw--w--w- 1 root root 4, 1 Jun 11 23:23 tty1 crw-rw-rw- 1 root root 4, 2 Jun 11 23:21 tty2 crw-rw-rw- 1 root root 4, 3 Jun 11 23:21 tty3 crw-rw-rw- 1 root other 4, 4 Jun 11 23:21 tty4 crw-rw-rw- 1 root other 4, 5 Jun 11 23:21 tty5 crw-rw-rw- 1 root root 4, 6 Jun 11 23:21 tty6 crw--w--w- 1 grahamc other 4, 7 Apr 15 1993 tty7 crw--w--w- 1 root root 4, 8 Apr 15 1993 tty8 crw-rw-rw- 1 root root 4, 64 Mar 30 1993 ttyS0 crw-rw-rw- 1 root users 4, 65 Mar 31 1993 ttyS1 crw-rw-rw- 1 root root 4, 66 Jan 23 1980 ttyS2 crw-rw-rw- 1 root root 4, 192 Jun 10 00:10 ttyp0 crw-rw-rw- 1 root root 4, 193 Apr 10 14:51 ttyp1 crw-rw-rw- 1 root root 4, 194 Aug 21 1994 ttyp2 crw-rw-rw- 1 root root 4, 195 Apr 12 1993 ttyp3 crw-rw-rw- 1 root tty 4, 196 Jan 3 1993 ttyp4 crw-rw-rw- 1 root tty 4, 197 Jan 3 1993 ttyp5 crw-rw-rw- 1 root tty 4, 198 Jan 3 1993 ttyp6 crw-rw-rw- 1 root tty 4, 199 Jan 3 1993 ttyp7 crw-rw-rw- 1 root tty 4, 200 Jan 3 1993 ttyp8 crw-rw-rw- 1 root tty 4, 201 Jan 3 1993 ttyp9 crw-rw-rw- 1 root tty 4, 202 Jan 3 1993 ttypa crw-rw-rw- 1 root tty 4, 203 Jan 3 1993 ttypb crw-rw-rw- 1 root tty 4, 204 Jan 3 1993 ttypc crw-rw-rw- 1 root tty 4, 205 Jan 3 1993 ttypd crw-rw-rw- 1 root tty 4, 206 Jan 3 1993 ttype crw-rw-rw- 1 root tty 4, 207 Jan 3 1993 ttypf -rw------- 1 root root 63488 Mar 14 1993 ttys0 crw-rw-rw- 1 root root 4, 67 Oct 14 1992 ttys3 crw-r--r-- 1 root root 1, 5 Aug 29 1992 zero /mnt/etc: total 108 -rw-r--r-- 1 root root 94 May 30 06:15 fstab -rwx------ 1 root root 25604 Mar 17 1993 getty* -rw------- 1 root root 566 Dec 30 1992 gettydefs -rw-rw-r-- 1 root shadow 321 Oct 3 1994 group -rwxr-xr-x 1 bin bin 9220 Mar 17 1993 halt* -rw-r--r-- 1 root root 26 Feb 19 19:07 host.conf -rw-r--r-- 1 root root 506 Feb 19 19:07 hosts -rwxr-xr-x 1 bin bin 17412 Mar 17 1993 init* -rw-r--r-- 1 root root 1354 Jun 3 23:42 inittab -rwxr-xr-x 1 root root 1478 Mar 17 18:29 issue* -rw-rw---- 1 root shadow 5137 Dec 4 1992 login.defs -rw-r--r-- 1 sysadmin bin 42 Mar 17 18:30 motd -rw-r--r-- 1 root shadow 525 Jun 11 23:24 passwd -rwxr-xr-x 1 root root 1476 Aug 17 1994 profile* -rw-r--r-- 1 root root 715 Feb 19 19:02 protocols drwxr-xr-x 2 root root 1024 May 30 06:05 rc.d/ -rwxr-xr-x 1 bin bin 9220 Mar 17 1993 reboot* -r--r--r-- 1 bin bin 57 Nov 28 1992 securetty -rw-r--r-- 1 root root 3316 Feb 19 19:01 services -rwxr-xr-x 1 bin bin 13316 Mar 17 1993 shutdown* -rwxr-xr-x 1 root root 3212 Apr 17 1993 swapoff* -rwxr-xr-x 1 root root 3212 Apr 17 1993 swapon* -rw-r--r-- 1 root root 817 Jun 11 23:23 termcap -rwxr-xr-x 1 root root 6188 Apr 17 1993 umount* -rw-r--r-- 1 root root 12264 Jun 11 23:22 utmp -rw-r--r-- 1 root root 56 Jun 11 23:22 wtmp /mnt/etc/rc.d: total 4 -rwxr-xr-- 1 root root 450 May 30 06:05 rc.0* -rwxr-xr-- 1 root root 390 May 30 06:05 rc.K* -rwxr-xr-- 1 root root 683 May 30 06:06 rc.M* -rwxr-xr-- 1 root root 498 Jun 11 18:44 rc.S* /mnt/home: total 0 /mnt/lib: total 287 -rwxr-xr-x 1 root root 17412 Jun 11 23:24 ld.so* lrwxrwxrwx 1 root root 14 Jun 11 23:24 libc.so.4 -> libc.so.4.5.21* -rwxr-xr-x 1 root root 623620 May 22 1994 libc.so.4.5.21* /mnt/lost+found: total 0 /mnt/mnt: total 0 /mnt/proc: total 0 /mnt/root: total 0 /mnt/sbin: total 15 -rwxr-xr-x 1 root root 16885 Jun 13 1994 update* /mnt/tmp: total 0 /mnt/usr: total 1 drwxr-xr-x 2 root root 1024 May 30 05:49 bin/ /mnt/usr/bin: total 217 -rwxr-xr-x 1 root root 1560 Sep 17 1992 basename* -rws--x--x 1 root root 8232 Jan 16 1993 chsh* -rwxr-xr-x 1 root root 1308 Jan 23 1980 clear* -rwxr-xr-x 1 root other 91136 Sep 4 1992 elvis* -rwxr-xr-x 1 root root 13252 Sep 17 1992 ls* -rwxr-xr-x 1 bin bin 21504 Oct 2 1992 more* -rwxr-xr-x 1 root other 91136 Sep 4 1992 vi* /mnt/util: total 0 /mnt/var: total 3 drwxr-xr-x 2 root root 1024 May 30 05:58 adm/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 logs/ drwxr-xr-x 2 root root 1024 Jun 11 23:24 run/ /mnt/var/adm: total 0 -rw-r--r-- 1 root root 0 May 30 05:58 utmp -rw-r--r-- 1 root root 0 May 30 05:58 wtmp /mnt/var/logs: total 0 /mnt/var/run: total 0 4.1.2. Utility Disk ls-lR Directory Listing The utility listing is of a diskette mounted at /mnt. total 15 drwx------ 2 root root 1024 Jun 18 19:57 bin/ drwxr-xr-x 2 root root 12288 Jun 18 19:57 lost+found/ drwx------ 2 root root 1024 Jun 18 19:57 sbin/ drwxr-xr-x 4 root root 1024 May 5 16:30 usr/ /mnt/bin: total 13 -rwxr-xr-x 1 root root 3180 Apr 10 1993 free* -rwxr-xr-x 1 root root 10687 Feb 10 1994 pwd* -rwx--x--x 1 root root 3672 Nov 17 1992 rdev* /mnt/lost+found: total 0 /mnt/sbin: total 18 -rwxr-xr-x 1 root root 16336 Jun 18 14:31 insmod* -rwxr-xr-x 1 root root 68 Jun 18 14:31 lsmod* lrwxrwxrwx 1 root root 6 Jun 18 19:57 rmmod -> insmod* /mnt/usr: total 2 drwx------ 2 root root 1024 Jun 18 19:57 bin/ drwxr-xr-x 3 root root 1024 Jun 18 19:57 local/ /mnt/usr/bin: total 411 -rwxr-xr-x 1 root bin 111616 Sep 9 1992 awk* -rwxr-xr-x 1 root root 41984 Dec 23 1992 cpio* -rwxr-xr-x 1 root root 50176 Dec 23 1992 find* -rwxr-xr-x 1 root root 115712 Sep 17 1992 gawk* -rwxr-xr-x 1 root bin 37888 Sep 4 1992 grep* -rwxr-xr-x 1 root root 63874 May 1 1994 gzip* -rwxr-xr-x 1 root root 2044 Sep 17 1992 kill* -rwx--x--x 1 root root 3132 Jan 24 1993 mt* -rwxr-xr-x 1 root root 3416 Sep 22 1992 strings* -rwxr-xr-x 1 root other 3848 Sep 4 1992 who* /mnt/usr/local: total 1 drwx------ 2 root root 1024 Jun 18 19:57 bin/ /mnt/usr/local/bin: total 374 -rwxr-xr-x 1 root root 155542 Jun 18 17:07 ftape.o* -rwxr-xr-x 1 root root 226308 Jun 13 1994 tar* 4.2. Shell Scripts to Build Diskettes These shell scripts are provided as examples only. I no longer use them because I now use and recommend Scott Burkett's Bootkit package to manage rescue diskette contents and creation. Bootkit is based on these scripts, and does essentially the same thing, but it is much tidier, nicer and easier to use. However, the sample shell scripts here will still provide working diskettes. There are two shell scripts: ╖ mkroot - builds a root or boot/root diskette. ╖ mkutil - builds a utility diskette. Both are currently configured to run in the parent directory of boot_disk and util_disk, each of which contains everything to be copied to it's diskette. Note that these shell scripts will *NOT* automatically set up and copy all the files for you - you work out which files are needed, set up the directories and copy the files to those directories. The shell scripts are samples which will copy the contents of those directories. Note that they are primitive shell scripts and are not meant for the novice user. The scripts both contain configuration variables at the start which allow them to be easily configured to run anywhere. First, set up the model directories and copy all the required files into them. To see what directories and files are needed, have a look at the sample directory listings in the previous sections. Check the configuration variables in the shell scripts and change them as required before running the scripts. 4.2.1. mkroot - Make Root or Boot/Root Diskette ______________________________________________________________________ # mkroot: make a boot/boot disk - creates a boot/root diskette # by building a file system on it, then mounting it and # copying required files from a model. # Note: the model to copy from from must dirst be set up, # then change the configuration variables below to suit # your system. # # usage: mkroot [nokernel] # if the parameter is omitted, then the kernel and LILO # are copied. # Copyright (c) Graham Chapman 1995. All rights reserved. # Permission is granted for this material to be freely # used and distributed, provided the source is acknowledged. # No warranty of any kind is provided. You use this material # at your own risk. # Configuration variables... BOOTDISKDIR=./boot_disk # name of boot disk directory MOUNTPOINT=./mnt # temporary mount point for diskette LILODIR=/sbin # directory containing lilo LILOBOOT=/boot/boot.b # lilo boot sector LILOMSG=./lilo.msg # lilo message to display at boot time LILOCONFIG=./lilo.conf # lilo parms for boot/root diskette DISKETTEDEV=/dev/fd0 # device name of diskette drive echo $0: create boot/root diskette echo Warning: data on diskette will be overwritten! echo Insert diskette in $DISKETTEDEV and and press any key... read anything mke2fs $DISKETTEDEV if [ $? -ne 0 ] then echo mke2fs failed exit fi mount -t ext2 $DISKETTEDEV $MOUNTPOINT if [ $? -ne 0 ] then echo mount failed exit fi # copy the directories containing files for i in bin etc lib do cp -dpr $BOOTDISKDIR/$i $MOUNTPOINT done # copy dev *without* trying to copy the files in it cp -dpR $BOOTDISKDIR/dev $MOUNTPOINT # create empty directories required mkdir $MOUNTPOINT/proc mkdir $MOUNTPOINT/tmp mkdir $MOUNTPOINT/mnt mkdir $MOUNTPOINT/usr # copy the kernel if [ "$1" != "nokernel" ] then echo "Copying kernel" cp $BOOTDISKDIR/zImage $MOUNTPOINT echo kernel copied # setup lilo cp $LILOBOOT $MOUNTPOINT cp $LILOMSG $MOUNTPOINT $LILODIR/lilo -C $LILOCONFIG echo LILO installed fi umount $MOUNTPOINT echo Root diskette complete ______________________________________________________________________ 4.2.2. mkutil - Make Utility Diskette ______________________________________________________________________ # mkutil: make a utility diskette - creates a utility diskette # by building a file system on it, then mounting it and # copying required files from a model. # Note: the model to copy from from must first be set up, # then change the configuration variables below to suit # your system. # Copyright (c) Graham Chapman 1995. All rights reserved. # Permission is granted for this material to be freely # used and distributed, provided the source is acknowledged. # No warranty of any kind is provided. You use this material # at your own risk. # Configuration variables... UTILDISKDIR=./util_disk # name of directory containing model MOUNTPOINT=./mnt # temporary mount point for diskette DISKETTEDEV=/dev/fd0 # device name of diskette drive echo $0: create utility diskette echo Warning: data on diskette will be overwritten! echo Insert diskette in $DISKETTEDEV and and press any key... read anything mke2fs $DISKETTEDEV if [ $? -ne 0 ] then echo mke2fs failed exit fi # Any file system type would do here mount -t ext2 $DISKETTEDEV $MOUNTPOINT if [ $? -ne 0 ] then echo mount failed exit fi # copy the directories containing files cp -dpr $UTILDISKDIR/bin $MOUNTPOINT umount $MOUNTPOINT echo Utility diskette complete ______________________________________________________________________ 5. FAQ 5.1. Q. How can I make a boot disk with a XXX driver? The easiest way is to obtain a Slackware kernel from your nearest Slackware mirror site. Slackware kernels are generic kernels which atttempt to include drivers for as many devices as possible, so if you have a SCSI or IDE controller, chances are that a driver for it is included in the Slackware kernel. Go to the a1 directory and select either IDE or SCSI kernel depending on the type of controller you have. Check the xxxxkern.cfg file for the selected kernel to see the drivers which have been included in that kernel. If the device you want is in that list, then the corresponding kernel should boot your computer. Download the xxxxkern.tgz file and copy it to your boot diskette as described above in the section on making boot disks. You must then check the root device in the kernel, using the rdev command: rdev zImage Rdev will then display the current root device in the kernel. If this is not the same as the root device you want, then use rdev to change it. For example, the kernel I tried was set to /dev/sda2, but my root scsi partition is /dev/sda8. To use a root diskette, you would have to use the command: rdev zImage /dev/fd0 If you want to know how to set up a Slackware root disk as well, that's outside the scope of this HOWTO, so I suggest you check the Linux Install Guide or get the Slackware distribution. See the section in this HOWTO titled "References". 5.2. Q. How do I update my boot floppy with a new kernel? Just copy the kernel to your boot diskette using the dd command for a boot diskette without a filesystem, or the cp command for a boot/root disk. Refer to the section in this HOWTO titled "Boot" for details on creating a boot disk. The description applies equally to updating a kernel on a boot disk. 5.3. Q. How do I remove LILO so that I can use DOS to boot again? This is not really a Bootdisk topic, but it is asked so often, so: the answer is, use the DOS command: FDISK /MBR MBR stands for Master Boot Record, and it replaces the boot sector with a clean DOS one, without affecting the partition table. Some purists disagree with this, but even the author of LILO, Werner Almesberger, suggests it. It is easy, and it works. You can also use the dd command to copy the backup saved by LILO to the boot sector - refer to the LILO documentation if you wish to do this. 5.4. Q. How can I boot if I've lost my kernel AND my boot disk? If you don't have a boot disk standing by, then probably the easiest method is to obtain a Slackware kernel for your disk controller type (IDE or SCSI) as described above for "How do I make a boot disk with a XXX driver?". You can then boot your computer using this kernel, then repair whatever damage there is. The kernel you get may not have the root device set to the disk type and partition you want. For example, Slackware's generic scsi kernel has the root device set to /dev/sda2, whereas my root Linux partition happens to be /dev/sda8. In this case the root device in the kernel will have to be changed. You can still change the root device and ramdisk settings in the kernel even if all you have is a kernel, and some other operating system, such as DOS. Rdev changes kernel settings by changing the values at fixed offsets in the kernel file, so you can do the same if you have a hex editor available on whatever systems you do still have running - for example, Norton Utilities Disk Editor under DOS. You then need to check and if necessary change the values in the kernel at the following offsets: 0x01F8 Low byte of RAMDISK size 0x01F9 High byte of RAMDISK size 0x01FC Root minor device number - see below 0X01FD Root major device number - see below The ramdisk size is the number of blocks of ramdisk to create. If you want to boot from a root diskette then set this to decimal 1440, which is 0x05A0, thus set offset 0x01F8 to 0xA0 and offset 0x01F9 to 0x05. This will allocate enough space for a 1.4Mb diskette. The major and minor device numbers must be set to the device you want to mount your root filesystem on. Some useful values to select from are: device major minor /dev/fd0 2 0 1st floppy drive /dev/hda1 3 1 partition 1 on 1st IDE drive /dev/sda1 8 1 partition 1 on 1st scsi drive /dev/sda8 8 8 partition 8 on 1st scsi drive Once you have set these values then you can write the file to a diskette using either Norton Utilities Disk Editor, or a program called rawrite.exe. This program is included in several distributions, including the SLS and Slackware distributions. It is a DOS program which writes a file to the "raw" disk, starting at the boot sector, instead of writing it to the file system. If you use Norton Utilities, then you must write the file to a physical disk starting at the beginning of the disk. 5.5. Q. How can I make extra copies of boot/root diskettes? It is never desirable to have just one set of rescue disks - 2 or 3 should be kept in case one is unreadable. The easiest way of making copies of any diskettes, including bootable and utility diskettes, is to use the dd command to copy the contents of the original diskette to a file on your hard drive, and then use the same command to copy the file back to a new diskette. Note that you do not need to, and should not, mount the diskettes, because dd uses the raw device interface. To copy the original, enter the command: dd if=devicename of=filename where devicename the device name of the diskette drive and filename the name of the file where you want to copy to For example, to copy from /dev/fd0 to a temporary file called /tmp/diskette.copy, I would enter the command: dd if=/dev/fd0 of=/tmp/diskette.copy Omitting the "count" parameter, as we have done here, means that the whole diskette of 2880 (for a high-density) blocks will be copied. To copy the resulting file back to a new diskette, insert the new diskette and enter the reverse command: dd if=filename of=devicename Note that the above discussion assumes that you have only one diskette drive. If you have two of the same type, then you can copy diskettes using a command like: dd if=/dev/fd0 of=/dev/fd1 5.6. Q. How can I boot without typing in "ahaxxxx=nn,nn,nn" every time? Where a disk device cannot be autodetected it is necessary to supply the kernel with a command device parameter string, such as: aha152x=0x340,11,3,1 This parameter string can be supplied in several ways using LILO: ╖ By entering it on the command line every time the system is booted via LILO. This is boring, though. ╖ By using the LILO "lock" keyword to make it store the command line as the default command line, so that LILO will use the same options every time it boots. ╖ By using the APPEND statement in the lilo config file. Note that the parameter string must be enclosed in quotes. For example, a sample command line using the above parameter string would be: zImage aha152x=0x340,11,3,1 root=/dev/sda1 lock This would pass the device parameter string through, and also ask the kernel to set the root device to /dev/sda1 and save the whole command line and reuse it for all future boots. A sample APPEND statement is: APPEND = "aha152x=0x340,11,3,1" Note that the parameter string must NOT be enclosed in quotes on the command line, but it MUST be enclosed in quotes in the APPEND statement. Note also that for the parameter string to be acted on, the kernel must contain the driver for that disk type. If it does not, then there is nothing listening for the parameter string, and you will have to rebuild the kernel to include the required driver. For details on rebuilding the kernel, cd to /usr/src/linux and read the README, and read the Linux FAQ and Installation HOWTO. Alternatively you could obtain a generic kernel for the disk type and install that. Readers are strongly urged to read the LILO documentation before experimenting with LILO installation. Incautious use of the "BOOT" statement can damage partitions. 5.7. Q. How can I create an oversize ramdisk filesystem? An oversize ramdisk filesystem is a filesystem in a ramdisk larger than the size of the root disk it was loaded from. This can be extremely useful when using Ftape, which requires exclusive use of the floppy disk controller (see the Ftape HOWTO for details.) Two things are required: create an oversize file system on the root diskette, and then patch the kernel so that it will not try to load blocks off the end of the diskette. To create an oversize filesystem, two methods are possible: ╖ Use the "blocks" e2fsck parameter to specify the size of filesystem that you eventually want in the ramdisk. For example: mke2fs /dev/fd0 3000 will create a filesystem on the diskette of 3000 1Kb blocks. The diskette only has 1440 blocks, but mke2fs does not care about this. E2fs will care about it if you try to use more than 1440 blocks of data (allowing for blocks used as inodes and reserved etc), but up to this point it is quite safe. You will soon find out if you try to load too much on the diskette because an I/O error will result. ╖ Create a partition on your hard disk as large as the filesystem you want on the ramdisk. Then create a filesystem on it and load in the files you want. Then use dd to copy only the first 1440 blocks to diskette, and then check that there was nothing in the uncopied part of the filesystem. For example: dd if=/dev/hdb of=/dev/fd0 bs=1024 count=1440 dd if=/dev/hdb of=tailpart bs=1024 skip=1440 cmp -l tailparm /dev/zero Of the two, I prefer the first method - it appears easier and safer. The second thing required to get an oversized filesystem is to get the kernel to stop loading at the end of the physical diskette when it tries to load the root diskette into ramdisk. To do this, a simple patch can be applied to the ramdisk driver, which should be found in /usr/src/linux/drivers/block/ramdisk.c. The following patch has been contributed by Bruce Elliot. It is for kernel version 1.2.0, but it should be fairly easy to apply to later versions. Even if the patch will not apply, the code is not complex, so the patch could easily be modified until it worked. ================================================================= X--- ramdisk.c~ Mon Jan 23 13:04:09 1995 X+++ ramdisk.c Mon May 29 00:54:52 1995 X@@ -113,6 +113,7 @@ X (struct ext2_super_block *)&sb; X int block, tries; X int i = 1; X+ int fblocks; X int nblocks; X char *cp; X X@@ -168,12 +169,16 @@ X nblocks, rd_length >> BLOCK_SIZE_BITS); X return; X } X- printk("RAMDISK: Loading %d blocks into RAM disk", nblocks); X+ fblocks = blk_size[MAJOR(ROOT_DEV)][MINOR(ROOT_DEV)]; X+ if (fblocks > nblocks) X+ fblocks = nblocks; X+ printk("RAMDISK: Loading %d blocks into %d block filesystem " X+ "in RAM disk", fblocks, nblocks); X X /* We found an image file system. Load it into core! */ X cp = rd_start; X- while (nblocks) { X- if (nblocks > 2) X+ while (fblocks) { X+ if (fblocks > 2) X bh = breada(ROOT_DEV, block, BLOCK_SIZE, 0, PAGE_SIZE); X else X bh = bread(ROOT_DEV, block, BLOCK_SIZE); X@@ -184,7 +189,7 @@ X } X (void) memcpy(cp, bh->b_data, BLOCK_SIZE); X brelse(bh); X- if (!(nblocks-- & 15)) printk("."); X+ if (!(fblocks-- & 15)) printk("."); X cp += BLOCK_SIZE; X block++; X i++; ================================================================= With this patch, the kernel stops loading at the end of the physical diskette, leaving a filesystem larger than the disk. Some warnings: I have been able to create stable ramdisk filesystems in this fashion of 3500 blocks, but if I try 3600 or more then the kernel collapses with an error something like "fixup table corrupt". I have not been able to track down why, but obviously something is overflowing. Up to 3500 blocks, though, I have had no problems. 5.8. Q. At boot time, I get error A: cannot execute B. Why? There are several cases of program names being hardcoded in various utilities. These cases do not occur everywhere, but they may explain why an executable apparently cannot be found on your system even though you can see that it is there. You can find out if a given program has the name of another hardcoded by using the "strings" command and piping the output through grep. Known examples of hardcoding are: ╖ Shutdown in some versions has /etc/reboot hardcoded, so reboot must be placed in the /etc directory. ╖ Init has caused problems for at least one person, with the kernel being unable to find init. To fix these problems, either move the programs to the correct directory, or change configuration files (e.g. inittab) to point to the correct directory. If in doubt, put programs in the same directories as they are on your hard disk, and use the same inittab and /etc/rc.d files as they appear on your hard disk. 6. References In this section, vvv is used in package names in place of the version, to avoid referring here to specific versions. When retrieving a package, always get the latest version unless you have good reasons for not doing so. 6.1. LILO - Linux Loader Written by Werner Almesberger. Excellent boot loader, and the documentation includes information on the boot sector contents and the early stages of the boot process. Ftp from: tsx-11.mit.edu: /pub/linux/packages/lilo/lilo.vvv.tar.gz also on sunsite and mirror sites. 6.2. Linux FAQ and HOWTOs These are available from many sources. Look at the usenet newsgroups news.answers and comp.os.linux.announce. Ftp from: sunsite.unc.edu:/pub/Linux/docs ╖ FAQ is in /pub/linux/docs/faqs/linux-faq ╖ HOWTOs are in /pub/Linux/docs/HOWTO For WWW, start at the Linux documentation home page: http://sunsite.unc.edu/mdw/linux.html If desperate, send mail to: mail-server@rtfm.mit.edu with the word "help" in the message, then follow the mailed instructions. Note: if you haven't read the Linux FAQ and related documents such as the Linux Installation HOWTO and the Linux Install Guide, then you should not be trying to build boot diskettes. 6.3. Rescue Packages 6.3.1. Bootkit Written by Scott Burkett. Bootkit provides a flexible menu-driven framework for managing rescue disk creation and contents. It uses the Dialog package to provide nice menus, and a straight-forward directory tree to contain definitions of rescue disk contents. The package includes samples of the main files needed. The package aims to provide only the framework; it is up to the user to work out what to put on the disks and set up the config files accordingly. For those users who don't mind doing this, it is a good choice. I use this package myself. Ftp from: sunsite.unc.edu: /pub/Linux/system/Recovery/Bootkit- vvv.tar.gz 6.3.2. CatRescue Written by Oleg Kibirev. This package concentrates on saving space on the rescue diskettes by extensive use of compression, and by implementing executables as shells scripts. The doco includes some tips on what to do in various disaster situations. Ftp from: gd.cs.csufresno.edu/pub/sun4bin/src/CatRescue100.tgz 6.3.3. Rescue Shell Scripts Written by Thomas Heiling. This contains shell scripts to produce boot and boot/root diskettes. It has some dependencies on specific versions of other software such as LILO, and so might need some effort to convert to your system, but it might be useful as a starting point if you wanted more comprehensive shell scripts than are provided in this document. Ftp from: sunsite.unc.edu:/pub/Linux/system/Recovery/rescue.tgz 6.3.4. SAR - Search and Rescue Written by Karel Kubat. SAR produces a rescue diskette, using several techniques to minimize the space required on the diskette. The manual includes a description of the Linux boot/login process. Ftp from: ftp.icce.rug.nl:/pub/unix/SAR-vvv.tar.gz The manual is available via WWW from: http://www.icce.rug.nl/karel/programs/SAR.html 6.4. Slackware Distribution Apart from being one of the more popular Linux distributions around, it is also a good place to get a generic kernel. It is available from almost everywhere, so there is little point in putting addresses here.