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LINUX FREQUENTLY ASKED QUESTIONS WITH ANSWERS 06 Mar 1996 Ian Jackson <ijackson@gnu.ai.mit.edu> This is the list of Frequently Asked Questions about Linux, the free Unix for 386/486/586 [see Q1.1 `What is Linux ?' for more details]. It should be read in conjunction with the HOWTO documents, which are available in * ftp.funet.fi (128.214.6.100) : /pub/OS/Linux/doc/HOWTO * tsx-11.mit.edu (18.172.1.2) : /pub/linux/docs/HOWTO * sunsite.unc.edu (152.2.22.81) : /pub/Linux/docs/HOWTO and mirror sites thereof -- see Q2.5 `Where can I get Linux material by FTP ?'. See Q2.1 `Where can I get the HOWTOs and other documentation ?' for a list of the HOWTOs and more information. The INFO-SHEET and META-FAQ, found in the same place, also list other sources of Linux information. The Linux Documentation Project documentation is available on sunsite.unc.edu in /pub/Linux/docs/LDP. These documents (more are in preparation) are invaluable to the newcomer or for use as a reference work. Please check out these documents and this FAQ, especially Q12.1 `You still haven't answered my question !', before posting your question to a newsgroup. See Q13.2 `Formats in which this FAQ is available' for details of where to get the PostScript, Emacs Info, HTML (WWW) and plain ASCII versions of this document. A new version of this document appears approximately monthly. If this copy is more than a month old it may be out of date. =============================================================================== Index Section 1. Introduction and General Information Q1.1 What is Linux ? Q1.2 What software does it support ? Q1.3 Does it run on my computer ? What hardware is supported ? Q1.4 What ports to other processors are there ? Q1.5 How much hard disk space does Linux need ? Q1.6 Is Linux PD ? Copyrighted ? Section 2. Network sources and resources Q2.1 Where can I get the HOWTOs and other documentation ? Q2.2 Where should I look on the World Wide Web for Linux stuff ? Q2.3 What newsgroups are there for Linux ? Q2.4 How do I install Linux ? Q2.5 Where can I get Linux material by FTP ? Q2.6 I don't have FTP access. Where do I get Linux ? Q2.7 I don't have Usenet access. Where do I get information ? Q2.8 What mailing lists are there ? Q2.9 Are the newsgroups archived anywhere ? Section 3. Compatibility with other operating systems Q3.1 Can Linux share my disk with DOS ? OS/2 ? 386BSD ? Win95 ? Q3.2 How do I access files on my DOS partition or floppy ? Q3.3 Can I use my Stacked/DBLSPC/etc. DOS drive ? Q3.4 Can I access OS/2 HPFS partitions from Linux ? Q3.5 Can I access BSD FFS, SysV UFS, Mac, Amiga, etc filesystems ? Q3.6 Can I run Microsoft Windows programs under Linux ? Q3.7 How can I boot Linux from OS/2's Boot Manager ? Q3.8 How can I share a swap partition between Linux and MS Windows ? Section 4. Linux's handling of filesystems, disks and drives Q4.1 How can I get Linux to work with my large disk ? Q4.2 How can I undelete files ? Q4.3 Is there a defragmenter for ext2fs etc. ? Q4.4 How do I format and create a filesystem on a floppy ? Q4.5 I get nasty messages about inodes, blocks, and the suchlike Q4.6 My swap area isn't working. Q4.7 How do I remove LILO so my system boots DOS again ? Q4.8 Why can't I use fdformat except as root ? Q4.9 Is there something like Stacker or Doublespace for Linux ? Q4.10 My ext2fs partitions are checked each time I reboot. Q4.11 My root filesystem is read-only ! Q4.12 I have a huge /proc/kcore ! Can I delete it ? Q4.13 My AHA1542C doesn't work with Linux. Section 5. Porting, compiling and obtaining programs Q5.1 How do I port XXX to Linux ? Q5.2 What is ld.so and where do I get it ? Q5.3 Has anyone ported / compiled / written XXX for Linux ? Q5.4 Can I use code or a compiler compiled for a 486 on my 386 ? Q5.5 What does gcc -O6 do ? Q5.6 Where are <linux/*.h> and <asm/*.h> ? Q5.7 I get errors when I try to compile the kernel. Q5.8 How do I make a shared library ? Q5.9 My executables are (very) large. Q5.10 Does Linux support threads or lightweight processes ? Q5.11 Where can I get `lint' for Linux ? Q5.12 Where can I find `kermit' for Linux ? Section 6. Solutions to common miscellaneous problems Q6.1 free dumps core. Q6.2 My clock is very wrong. Q6.3 Setuid scripts don't seem to work. Q6.4 Free memory as reported by free keeps shrinking. Q6.5 When I add more memory it slows to a crawl. Q6.6 Some programs (e.g. xdm) won't let me log in. Q6.7 Some programs let me log in with no password. Q6.8 My machine runs very slowly when I run GCC / X / ... Q6.9 I can only log in as root. Q6.10 My screen is all full of weird characters instead of letters. Q6.11 I have screwed up my system and can't log in to fix it. Q6.12 I've discovered a huge security hole in rm ! Q6.13 lpr and/or lpd aren't working. Q6.14 Timestamps on files on msdos partitions are set incorrectly. Q6.15 How do I get LILO to boot the vmlinux file ? Section 7. How do I do this or find out that ... ? Q7.1 How can I get scrollback in text mode ? Q7.2 How do I switch virtual consoles ? How do I enable them ? Q7.3 How do I set the timezone ? Q7.4 What version of Linux and what machine name am I using ? Q7.5 How can I enable or disable core dumps ? Q7.6 How do I upgrade/recompile my kernel ? Q7.7 Can I have more than 3 serial ports by sharing interrupts ? Q7.8 How do I make a bootable floppy ? Q7.9 How do I remap my keyboard to UK, French, etc. ? Q7.10 How do I get NUM LOCK to default to on ? Q7.11 How can I have more than 128Mb of swap ? Section 8. Miscellaneous information and questions answered Q8.1 How do I program XYZ under Linux ? Q8.2 What's all this about ELF ? Q8.3 What is a .gz file ? And a .tgz ? And ... ? Q8.4 What does VFS stand for ? Q8.5 What is a BogoMip ? Q8.6 What is the Linux Journal and where can I get it ? Q8.7 How many people use Linux ? Q8.8 How should I pronounce Linux ? Section 9. Frequently encountered error messages Q9.1 Unknown terminal type linux and similar Q9.2 During linking I get Undefined symbol _mcount Q9.3 lp1 on fire Q9.4 INET: Warning: old style ioctl(IP_SET_DEV) called! Q9.5 ld: unrecognized option '-m486' Q9.6 GCC says Internal compiler error Q9.7 make says Error 139 Q9.8 shell-init: permission denied when I log in. Q9.9 No utmp entry. You must exec ... when I log in. Q9.10 Warning - bdflush not running Q9.11 Warning: obsolete routing request made. Q9.12 EXT2-fs: warning: mounting unchecked filesystem Q9.13 EXT2-fs warning: maximal count reached Q9.14 EXT2-fs warning: checktime reached Q9.15 df says Cannot read table of mounted filesystems Q9.16 fdisk says Partition X has different physical/logical ... Q9.17 fdisk: Partition 1 does not start on cylinder boundary Q9.18 fdisk says partition n has an odd number of sectors Q9.19 mtools says cannot initialise drive XYZ Q9.20 At the start of booting: Memory tight Q9.21 You don't exist. Go away. Section 10. The X Window System Q10.1 Does Linux support X Windows ? Q10.2 Where can I get an XF86Config for my system ? Q10.3 xterm logins show up strangely in who, finger Q10.4 I can't get X Windows to work right. Section 11. Questions applicable to very out-of-date software Q11.1 Emacs just dumps core. Q11.2 fdisk says cannot use nnn sectors of this partition Q11.3 GCC sometimes uses huge amounts of virtual memory and thrashes Q11.4 My keyboard goes all funny after I switch VC's. Section 12. How to get further assistance Q12.1 You still haven't answered my question ! Q12.2 What to put in a request for help Q12.3 I want to mail someone about my problem. Section 13. Administrative information and acknowledgements Q13.1 Feedback is invited Q13.2 Formats in which this FAQ is available Q13.3 Authorship and acknowledgements Q13.4 Disclaimer and Copyright =============================================================================== Section 1. Introduction and General Information Q1.1 What is Linux ? Q1.2 What software does it support ? Q1.3 Does it run on my computer ? What hardware is supported ? Q1.4 What ports to other processors are there ? Q1.5 How much hard disk space does Linux need ? Q1.6 Is Linux PD ? Copyrighted ? ------------------------------------------------------------------------------- Question 1.1. What is Linux ? Linux is a Unix clone written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX compliance. It has all the features you would expect in a modern fully-fledged Unix, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management and TCP/IP networking. It runs mainly on 386/486/586-based PCs, using the hardware facilities of the 386 processor family (TSS segments et al) to implement these features. Ports to other architectures are underway [Q1.4 `What ports to other processors are there ?']. See the Linux INFO-SHEET [Q2.1 `Where can I get the HOWTOs and other documentation ?'] for more details. The Linux kernel is distributed under the GNU General Public License - see Q1.6 `Is Linux PD ? Copyrighted ?' for more details. ------------------------------------------------------------------------------- Question 1.2. What software does it support ? Linux has GCC, Emacs, X-Windows, all the standard Unix utilities, TCP/IP (including SLIP and PPP) and all the hundreds of programs that people have compiled or ported for it. There is a DOS emulator (look on tsx-11.mit.edu in /pub/linux/ALPHA/dosemu) which can run DOS itself and some (but not all) DOS applications. I'm told that it can now run Windows 3.1 in Enhanced Mode. An iBCS2 (Intel Binary Compatibility Standard) emulator for SVR4 ELF and SVR3.2 COFF binaries is at a fairly advanced stage of development. See the file /pub/linux/BETA/ibcs2/README on tsx-11.mit.edu. Work is progressing on an emulator for Microsoft Windows binaries [Q3.6 `Can I run Microsoft Windows programs under Linux ?']; alternatively, I'm told that the DOS emulator team have been having some success getting MS Windows to run inside dosemu - there will be an announcement if and when they get it working. For more information see the INFO-SHEET, which is one of the the HOWTOs [Q2.1 `Where can I get the HOWTOs and other documentation ?']. See also Q5.1 `How do I port XXX to Linux ?'. Some companies have commercial software available, including Motif. They announce their availability in comp.os.linux.announce --- try searching the archives [Q2.9 `Are the newsgroups archived anywhere ?']. ------------------------------------------------------------------------------- Question 1.3. Does it run on my computer ? What hardware is supported ? You need a 386, 486 or 586, with at least 2Mb of RAM and a single floppy, to try it out. To do anything useful more RAM (4Mb to install most distributions, and 8Mb is highly recommended for running X) and a hard disk are required. VESA local bus and PCI are both supported. There are problems with machines using MCA (IBM's proprietary bus), mainly to do with the hard disk controller. There is a developers' release for PS/2 ESDI drives on invaders.dcrl.nd.edu in /pub/misc/linux. Certain kinds of SCSI controllers also work, I understand. Work is in progress to create a suitable version of the Slackware distribution. I'm afraid I don't have any further details; you could try asking Arindam Banerji <axb@defender.dcrl.nd.edu>. Linux runs on 386 family based laptops, with X on most of them. There is a relevant Web page at http://www.cs.utexas.edu/users/kharker/linux-laptop/. For details of exactly which PC's, video cards, disk controllers, etc. work see the INFO-SHEET and the Hardware HOWTO [Q2.1 `Where can I get the HOWTOs and other documentation ?']. There is a port of Linux to the 8086, known as the Embeddable Linux Kernel Subset (ELKS). This is a 16-bit subset of the Linux kernel which will mainly be used for embedded systems. See http://www.linux.org.uk/Linux8086.html for more information. Linux will never run fully on an 8086 or '286, because it requires task-switching and memory management facilities not found on these processors. Recent versions of Linux (1.3.35 and later) do support multiprocessor machines, though this is still rather less stable than one would hope. ------------------------------------------------------------------------------- Question 1.4. What ports to other processors are there ? A project has been underway for a while to port Linux to suitable 68000-series based systems such as Amigas and Ataris. This has now reached beta test quality and there is an X server. There is a linux-680x0 mailing list [Q2.8 `What mailing lists are there ?'], and a Linux/68K FAQ at http://pfah.informatik.uni-kl.de:8000/pers/jmayer/linux68k-faq and on tsx-11.mit.edu in /pub/linux/680x0/FAQ; further information is at http://www-users.informatik.rwth-aachen.de/~hn/linux68k.html. There is a mailing list for the Atari port - mail <majordomo@phil.uni-sb.de> with a body containing only subscribe atarix - and an ftp area on ftp.phil.uni-sb.de in /pub/atari/linux. There used to be a project to port Linux too 68K-based Macintoshes, but its FTP site disappeared recently and the project appears to be dead. There is a port to the PowerPC. As of the 7th of July it is rather fragmentary and cannot recompile itself, and only supports Motorola 1603 boards. Work on Motorola Ultra, PowerStack, RS/6000 and NuBus machines continues. If you wish to contribute to the project join the linux-ppc mailing list [Q2.8 `What mailing lists are there ?']. There is a FAQ on liber.stanford.edu in /pub/linuxppc/linux-ppc-FAQ or on the WWW at http://liber.stanford.edu/linuxppc/linux-ppc-FAQ.html. Apple and the OSF are working on a PowerPC port of Linux based on the OSF Mach microkernel. See http://mklinux.apple.com/. There is a port to the 64-bit DEC Alpha/AXP. See http://www.azstarnet.com/~axplinux/. Again, there is a mailing list at vger.rutgers.edu. Ralf Baechle is working on a port to the MIPS, initially for the R4600 on Deskstation Tyne machines. The Linux/MIPS FAQ is available on the WWW and in the MIPS port area on ftp.waldorf-gmbh.de in /pub/linux/mips. There is also a MIPS channel on the Linux Activists mailserver and a linux-mips mailing list [Q2.8 `What mailing lists are there ?']. Interested people may mail their questions and offers of assistance to <linux@waldorf-gmbh.de>. There are currently two ports of Linux to the ARM family of processors ongoing; one of these is to the ARM3 as fitted to the Acorn A5000, and includes I/O drivers for the 82710/11 as appropriate, and the other is to the ARM610 as fitted to the Acorn Risc PC. The Risc PC port is currently in its early to middle stages, owing to the need to rewrite much of the memory handling. The A5000 port is in restricted beta testing; a release is likely fairly soon. For more up to date information watch the newsgroup comp.sys.acorn.misc, or look on the WWW at http://whirligig.ecs.soton.ac.uk/~rmk92/armlinux.html; if you want to volunteer you should contact Martin Ebourne <mje@soton.ac.uk>. David Miller is working on a port to the Sparc. It is at a very early stage; people who are willing to dedicate lots of time and have access to Sparc boxes for testing should get in touch with <davem@caip.rutgers.edu>. None of the above ports will be capable of running Linux/386 binaries. Linux port to the Aleph One 486 card (*not* the second processor card for the Risc PC yet, but the original PC-on-a-podule card) has been completed and appears stable. Full details on this version, and updates on general ports in progress, can be found on the WWW at http://www.ph.kcl.ac.uk/~amb/linux.html. ------------------------------------------------------------------------------- Question 1.5. How much hard disk space does Linux need ? 10Mb for a very minimal installation, suitable for trying it out and not much else. You can squeeze a more complete installation including X Windows into 80Mb. Installating almost all of Debian 0.93R6 takes around 500Mb, including some space for user files and spool areas. ------------------------------------------------------------------------------- Question 1.6. Is Linux PD ? Copyrighted ? The Linux kernel copyright belongs to Linus Torvalds. He has placed it under the GNU General Public Licence, which basically means that you may freely copy, change and distribute it, but that you may not impose any restrictions on further distribution, and that you must make the source code available. This is not the same as Public Domain (see the Copyright FAQ, available on rtfm.mit.edu in /pub/usenet/news.answers/law/Copyright-FAQ, for details). Full details are in the file COPYING in the Linux kernel sources (probably in /usr/src/linux on your system). The licences of the utilities and programs which come with the installations vary; much of the code is from the GNU Project at the Free Software Foundation, and is also under the GPL. Note that discussion about the merits or otherwise of the GPL should be posted to gnu.misc.discuss and not to the comp.os.linux groups. =============================================================================== Section 2. Network sources and resources Q2.1 Where can I get the HOWTOs and other documentation ? Q2.2 Where should I look on the World Wide Web for Linux stuff ? Q2.3 What newsgroups are there for Linux ? Q2.4 How do I install Linux ? Q2.5 Where can I get Linux material by FTP ? Q2.6 I don't have FTP access. Where do I get Linux ? Q2.7 I don't have Usenet access. Where do I get information ? Q2.8 What mailing lists are there ? Q2.9 Are the newsgroups archived anywhere ? ------------------------------------------------------------------------------- Question 2.1. Where can I get the HOWTOs and other documentation ? Look in the following places, and on sites that mirror them. * ftp.funet.fi (128.214.6.100) : /pub/OS/Linux/doc/HOWTO * tsx-11.mit.edu (18.172.1.2) : /pub/linux/docs/HOWTO * sunsite.unc.edu (152.2.22.81) : /pub/Linux/docs/HOWTO For a complete list of Linux FTP sites see Q2.5 `Where can I get Linux material by FTP ?'. If you don't have access to FTP try using the FTP-by-mail servers at ftpmail@decwrl.dec.com, ftpmail@doc.ic.ac.uk or ftp-mailer@informatik.tu-muenchen.de. A complete list of HOWTO's is available in the file HOWTO.INDEX in the docs/HOWTO directory at the FTP sites, or on the Web at http://sunsite.unc.edu/mdw/HOWTO/HOWTO-INDEX.html but here is a (possibly incomplete) list: Linux INFO-SHEET Linux META-FAQ Bootdisk HOWTO Busmouse HOWTO CDROM HOWTO Commercial HOWTO Cyrillic HOWTO DOSEMU HOWTO Danish HOWTO Distribution HOWTO ELF HOWTO Ethernet HOWTO Firewall HOWTO Ftape HOWTO German HOWTO HAM HOWTO Hardware HOWTO Installation HOWTO JE HOWTO Kernel HOWTO MGR HOWTO Electronic Mail HOWTO NET-2 HOWTO NIS HOWTO News HOWTO PCI-HOWTO PCMCIA HOWTO PPP HOWTO Printing HOWTO SCSI HOWTO SCSI Programming HOWTO Serial HOWTO Sound HOWTO Term HOWTO Tips HOWTO UPS HOWTO UUCP HOWTO XFree86 HOWTO More of these documents are always in preparation. You should check in nearby directories on the FTP sites if you can't find the answer in one of the HOWTOs. There are also several mini-HOWTOs on sunsite.unc.edu in the /pub/Linux/docs/HOWTO/mini directory. The file WRITING contains information on how to write a new HOWTO. The HOWTOs are coordinated by Greg Hankins, <gregh@cc.gatech.edu>. The `books' produced by the Linux Documentation Project are available in /pub/Linux/docs/LDP on sunsite.unc.edu. Please read them if you are new to Unix and Linux. Here is a list of those released so far: * The Linux Documentation Project manifesto * Installation and Getting Started Guide * The Kernel Hacker's Guide * Network Administration Guide * Linux System Administrator's Guide ------------------------------------------------------------------------------- Question 2.2. Where should I look on the World Wide Web for Linux stuff ? Matt Welsh maintains the Linux Documentation Project Home Page, at http://sunsite.unc.edu/mdw/linux.html. This page refers to all the FAQs and HOWTOs, both those which are available in HTML (WWW) format, like this FAQ, and those which aren't. ------------------------------------------------------------------------------- Question 2.3. What newsgroups are there for Linux ? There are ten international Usenet newsgroups devoted to Linux. comp.os.linux.announce is the moderated announcements group; you should read this if you intend to use Linux. Submissions for that group should be emailed to linux-announce@news.ornl.gov. comp.os.linux.answers contains all the FAQs, HOWTOs and other important documentation. You should subscribe to this too. Also worth reading are the other groups in the comp.os.linux.* hierarchy -- you may find that many common problems are too recent to find in this FAQ but are answered in the newsgroups. These groups are comp.os.linux.setup, comp.os.linux.hardware, comp.os.linux.networking, comp.os.linux.x, comp.os.linux.development.apps, comp.os.linux.development.system, comp.os.linux.advocacy and comp.os.linux.misc. Remember that since Linux is a Unix clone, most all of the material in comp.unix.* and comp.windows.x.* groups will be relevant. Apart from hardware considerations, and some obscure or very technical low-level issues, you'll find that these groups are the right place to start. Please read Q12.1 `You still haven't answered my question !' before posting, and make sure you post to the right newsgroup -- see `Welcome to the comp.os.linux.* hierarchy' which is posted every two weeks to comp.os.linux.announce, comp.os.linux.answers and other groups. Crossposting between different comp.os.linux.* groups is rarely a good idea. There may well be Linux groups local to your institution or area - check there first. The groups comp.os.linux.development, comp.os.linux.admin and comp.os.linux.help were superseded in a recent newsgroup reorganisation. You should no longer use them. See also Q2.7 `I don't have Usenet access. Where do I get information ?'. Other regional and local newsgroups also exist - you may find the traffic more manageable there. The French Linux newsgroup is fr.comp.os.linux; The German one is de.comp.os.linux. In Australia, try aus.computers.linux. In Croatia there is the moderated group hr.comp.linux.m. In Italy, it.comp.linux. ------------------------------------------------------------------------------- Question 2.4. How do I install Linux ? There are several pre-packaged releases of Linux available, including Debian, Red Hat and Slackware. Each contains the software you need to run Linux, ready to install and use. The exact details of which software is included and how to install them vary from release