Current Shareware 1994 January/SHAR194.ISO/misc/aix1025.zip/AIX_FAQ.1

Internet Message Format | 1993-10-27 | 55KB

Path: nlbbs!jaxsat!pagesat!decwrl!uunet!cs.utexas.edu!mavrick![e-mail]
From: [e-mail] (Luis Basto)
Newsgroups: comp.unix.aix,news.answers,comp.answers
Subject: AIX Frequently Asked Questions (Part 1 of 3)
Summary: This posting contains a list of Frequently Asked Questions and thei
 answers about AIX, IBM's version of Unix.
Keywords: AIX RS/6000 questions answers
Message-ID: <[e-mail]>
Date: 25 Oct 93 06:03:14 GMT
Expires: 15 Nov 93 01:23:45 GMT
Sender: [e-mail]
Reply-To: [e-mail] (Luis Basto)
Followup-To: comp.unix.aix
Lines: 1519
Approved: [e-mail]
Supersedes: <[e-mail]>

Archive-name: aix-faq/part1
Last-modified: October 25, 1993
Version: 2.42


Version: $Id: aix.faq,v 2.42 93/10/25 basto $

Frequently Asked Questions to AIX 3.x and IBM RS/6000
_____________________________________________________

This posting contains frequently asked questions and answers about the
IBM RS/6000 series workstations and AIX version 3. All input is very
welcome, please mail to [e-mail].

The list is split into three articles to pass thru most mailers. I'll
usually try to post them once a month to comp.unix.aix, news.answers,
and comp.answers. Please let your input continue as I am most thankful
for all of it.

If you see a From: line it means that whatever follows is either an
unabridged or slightly edited version of the input I have received, and
that I may not have verified its contents. If there is no From: line, I
probably know what I am talking about, and the entry is edited from
various sources.

All entries are numbered with major and minor subject number, e.g.
2.11. If the subject is preceded by an asterisk, that entry has been
changed or added since the last posting.

The comp.unix.aix group is for AIX on all IBM platforms -- RT, PS/2,
370, RS/6000 and mainframes (ESA based on OSF/1), but the traffic has
evolved to discuss predominantly AIX 3.x and the RS/6000. The
newsgroups comp.sys.ibm.pc.rt and comp.sys.ibm.ps2.hardware cover the
RT, mostly hardware and AOS 4.3, and on PS/2 hardware respectively.
Mark Whetzel posts FAQ lists about RTs in the rt and *.answers groups.
There are few to non-existent discussions on AIX/370 and AIX/ESA.

This article covers only AIX 3.x and the RS/6000, except when noted.

If you post questions to comp.unix.aix, please be sure to indicate:

- the machine type and brief configuration, e.g. Model 540, 64 MB RAM,
  48 MB swap space (this is actually bad), 1.2 GB XYZ hard drive, etc.

- the exact AIX version number, i.e. AIX 3.1 is NOT sufficient, whereas
  AIX 3.1.5 or AIX 3.1 with the 3005 update is. With 3.2 you should
  mention any significant ptfs using the U4xxxxx numbers.
______________________________________________________________________________

Table of contents:

1.0    General concepts
1.000  The AIX operating system - what is it?
1.000  I know neither Unix nor AIX - where do I find more information?
1.002  What is the Object Database?
1.003  How do I get rid of the verbose error messages?
1.004  Which release of AIX do I have?

1.1    SMIT, system administration, file systems
1.100  I am used to Unix systems programming, why should I learn SMIT?
1.101  How do I turn off the "running man" in smit?
1.102  How do I import an /etc/passwd or /etc/group file from another box?
1.103  Cleaning up utmp, who, and accounting problems
1.104  How to fsck the root filesystem
1.105  How can I unmount /usr to run fsck on it?
1.106  How do I shrink /usr?
1.107  How do I make a filesystem larger than 2 Gig?
1.108  How do I see/change system parameters like number of processes per user
1.109  How do I shrink the default paging space on hd6?
1.110  The swapper seems to use enormous amounts of paging space, why?
1.111  How much paging space do I need?
1.112  How do I mount a floppy disk as a filesystem?
1.113  How do I remove a committed lpp?
1.114  How can I recover space after installing updates?
1.115  Where are the AIX log files kept?
1.116  How can I log information about ftp accesses to a file?
1.117  How do I find a file name from the inode number?
1.118  How do I set up postscript accounting?
1.119  How do I create boot diskettes for 3.2?
1.120  Where can I find tools for performance monitoring?
1.121  How can I tell what virtual printer a print queue is using?
1.122  Two srcmstr's are less useful than one?
1.123  How do I set the tty name associated with a physical port?
1.124  How do I use mksysb to clone a system?
1.125  How do I retain timestamps with mksysb?
1.126  How can I find out the machine type?

1.2    Backups, tape
1.200  Some info about tape backups
1.201  How do I do remote backup?
1.202  How do I backup a multi-disk volume group?
1.203  How do I put multiple backups on a single 8mm tape?
1.204  How can I make an exact duplicate of a tape over the network?

1.3    Memory and process management
1.300  Some info about the memory management system
1.301  How much should I trust the ps memory reports?

1.4    Shells, commands, man pages, InfoExplorer
1.400* How do I make an informative prompt in the shell?
1.401  How do I set up ksh for emacs mode command line editing?
1.402  Listing files with ls causes a core dump
1.403  How do I put my own text into InfoExplorer?
1.404  InfoExplorer ASCII key bindings
1.405  How can I add new man pages to the system?

1.5    Video, Graphics, X11
1.500  Which release of X11 do I have?
1.501  How to prevent ctrl-alt-backspace from killing the X session
1.502  Who has a termcap/terminfo source for aixterm or the HFT console?
1.503  How can I look at PostScript files?  Why is "dpsexec" so lousy?
1.504  unix:0 vs `hostname`:0
1.505  VT100 key bindings for aixterm

1.6    Networks and communications
1.600* My named dies frequently, why?
1.601  How do I trace ethernet packets on an AIX system?
1.602  What is the authorized way of starting automount at boot time?
1.603  How do I set a tty port for both dial-in and dial-out?
1.604  How to move or copy whole directory trees across a network
1.605  How can I send mail to hosts that cannot be pinged?
1.606  How to setup dialup SLIP

1.7
1.8

1.9    Miscellaneous
1.900  SCSI-1 and SCSI-2 "interoperability" got you confused?
1.901  How to get your keyboard back after unplugging it from the 6000
1.902  How do I set up pcsim, the DOS emulator?
1.903  How do I transfer files between AIX and DOS disks?


2.00  C/C++
2.01  I cannot make alloca work
2.02  How do I compile my BSD programs?
2.03* Isn't the linker different from what I am used to?
2.04  How do I link my program with a non-shared /lib/libc.a?
2.05  How do I make my own shared library?
2.06  Linking my program fails with strange error, why?
2.07  What's with malloc()?
2.08  Why does xlc complain about 'extern char *strcpy()'
2.09  Why do I get 'Parameter list cannot contain fewer ....'
2.10  Why does xlc complain about '(sometype *)somepointer = something'
2.11  Some more common errors
2.12  Can the compiler generate assembler code?
2.13  Curses
2.14  How do I speed up linking?
2.15  What is deadbeef?
2.16  How do I statically link in 3.2?

3.00  Fortran and other compilers
3.01  I have problems mixing fortran and C code, why?
3.02  How do I statically bind fortran libraries and dynamically bind
      C libraries?
3.03  How do I check if a number is NaN?
3.04  Some info sources on IEEE floating point

4.00  GNU and Public Domain software
4.01  How do I find PD software?
4.02* Are there any ftp sites?
4.03  General hints
4.04  GNU Emacs
4.05  gcc/gdb
4.06  GNU Ghostscript
4.07  TeX
4.08  Perl
4.09  X-Windows
4.10  bash
4.11  Elm
4.12  Oberon 2.2
4.13* Kermit
4.14  Gnu dbm
4.15  tcsh
4.16  Kyoto Common Lisp
4.17* Tcl/Tk
4.18  Expect
4.19  Public domain software on CD
4.20* Andrew Toolkit

5.00  Third party products
5.01  IBM List of third party products
5.02  Disk/Tape/SCSI
5.03  Memory
5.04  Others
5.05  C++ compilers

6.00  Miscellaneous other stuff
6.01* Can I get support by e-mail?
6.02  List of useful faxes
6.03  List of 3.2 ptfs
6.04  Some RS232 hints
6.05  What publications are available for AIX and RS/6000?
6.06  Some acronyms
6.07  How do I get this by mailserver or ftp?
6.08  Hypertext version of the FAQ
6.09  Where can I send suggestions for tools?

7.00  Contributors

______________________________________________________________________________
1.000: The AIX operating system - what is it?

This is best answered by reading the text files in /usr/lpp/bos. The
README file there contains general information and the BSD files contain
useful information if you know BSD and/or System V.

The last release for the RT PC is 2.2.1. The latest release for PS/2s
and Intel architecture machines is AIX 1.3; for PS/2s only, 1.2.1. For
the RS/6000, there are two major levels, 3.1 and 3.2, and various
intermediate levels.


1.001: I know neither Unix nor AIX - where do I find more information?

Quite a number of questions posted to comp.unix.aix show that AIX is
people's first experience with Unix. If this is the case with you, you
are advised to look at the other newsgroups in the comp.unix hierarchy,
in particular comp.unix.questions (for basic questions) or
comp.unix.wizards (for difficult questions). These two groups have a
common FAQ posting as well.

If you need information about C programming, try comp.lang.c or comp.std.c,
the latter for Standard ANSI C issues.  comp.lang.c has a FAQ posting.


1.002: What is the Object Database?

The Object Database Manager, ODM, stored in /etc/objrepos,
/usr/lib/objrepos, and /usr/share/lib/objrepos is AIX's way of storing
all the system management information. Under most circumstances, only
SMIT or the commands SMIT call (see 1.100) should be used to change the
ODM.

A harmless way to look at the ODM is to use odmget <Class> where <Class>
is one of the files in /etc/objrepos.

Experienced users can use the ODM editor, odme, to navigate the ODM in
detail. Modifying the ODM should only be attempted if you know exactly
what you are doing.


1.003: How do I get rid of the verbose error messages?

Many of the messages from the Unix commands are available in different
languages. This is controlled by the LANG environment variable, the
default being En_US meaning English in the US. All the default messages
have a message number associated with them, e.g.:

$ cat no-such-file
cat: 0652-050 Cannot open no-such-file.

If you prefer the terser Unix-looking error message, set your
environment LANG to C, and you will get:

$ cat no-such-file
cat: Cannot open no-such-file.


1.004: Which release of AIX or other products do I have?

The command 'lslpp -h bos.obj' will show all lines referring to the BOS,
Basic Operating System.  E.g.:

Option Name          State      Event      Date      Release         User Name
-------------------- ---------- ---------- --------- --------------- ---------
bos.obj              INACTIVE   COMMIT     02/03/90  03.01.0000.0000 root
                     INACTIVE   APPLY      06/25/90  03.01.0000.0001 root
                     INACTIVE   COMMIT     06/25/90  03.01.0000.0001 root
                     INACTIVE   APPLY      11/16/90  03.01.0002.0015 root
                     INACTIVE   COMMIT     11/16/90  03.01.0002.0015 root
                     ACTIVE     COMMIT     05/07/91  03.01.0005.0012 root

gives the history for the BOS lpp.  The last line, column four, indicates
that this is release 3.1.5.

To see a listing of everything installed use lslpp -l '*', then use
lslpp with the -h option as above to get a history of a particular lpp.

3.1.5 is considered the "base" release for users running 3.1.  You
should be at least at this level.  If you request a ptf update you will
get 2010.  If you are at some level earlier than 3.1.5, you must first
apply 3.1.5, then 2010.  Customers using SNA should request the SNA
Quality Refresh update.  Support for 3.1 will end on December 31, 1993.

For AIX 3.2, it's a completely different scheme. You may come across
discussions on 3.2.0, 3.2.1, 3.2.2, or 3.2.3 extended. There is no
absolute way to tell which of these you are running since the newer
releases are simply 3.2.0 with some sets of PTFs added. These selective
fixes could mean there are literally thousands of slightly different
variations of 3.2 in use. Please see section 6 to request some useful
faxes to help with this number game.

AIX 3.2.4 resolves this confusion with a new option for lslpp. Use
'lslpp -m bos.obj' to show what level and update the system is running.
You can also use the new oslevel command. Unless you have a pressing
need (such as applications unsupported on 3.2.4), it is recommended that
you update to this level.

______________________________________________________________________________
1.100: I am used to Unix systems programming, why should I learn SMIT?

Using SMIT is probably very different from your normal way of doing
system administration, but could prove very useful in the long run. In
some areas, in particular TCP/IP, NFS, etc., you can also do things the
normal way, but it is unfortunately difficult to know exactly when the
normal way works. Again, always using SMIT is probably your best way
to go, even when you have to learn a new tool.

What SMIT actually does is build up commands with all required options
to perform the functions requested and execute them. The commands
called and the output they produce are stored in the files smit.script
and smit.log in your home directory. Looking in smit.script may teach
you more about system administration.


1.101: How do I turn off the "running man" in smit?

Use smitty, the standard curses version or add this line to your .kshrc file:
alias smit="smit -C"


1.102: How do I import an /etc/passwd or /etc/group file from another box?

Make sure that you run usrck, pwdck (/etc/passwd), and grpck
(/etc/group) to let AIX work its password/group magic.


1.103: Cleaning up utmp, who, and accounting problems
From: [e-mail] (Frederick Staats)

This applies if you are running an X11R5 xterm on 3.2.
Add this to the top of X11R5 mit/clients/xterm/main.c:

#ifdef AIXV3
#define USE_SYSV_UTMP
#define HAS_UTMP_UT_HOST
#define WTMP_FILENAME "/var/adm/wtmp"
#endif

And your utmp problems should go away.  If you want xterminal sessions
to go into the wtmp file you need to define -DWTMP in the Imakefile and
be sure the WTMP_FILENAME is set to the right place.

The following program by [e-mail] (John F. Haugh)
if run in the background by root will clean up the utmp file.

#include <sys/types.h>
#include <utmp.h>
#include <fcntl.h>

main ()
{
        int     fd;
        struct  utmp    utmp;

        while (1) {
                if ((fd = open ("/etc/utmp", O_RDWR)) < 0)
                        exit (1);

                while (read (fd, &utmp, sizeof utmp) == sizeof utmp) {
                        if (utmp.ut_type == USER_PROCESS &&
                                        kill (utmp.ut_pid, 0) != 0) {
                                lseek (fd, - (long) sizeof utmp, 1);
                                utmp.ut_type = DEAD_PROCESS;
                                write (fd, &utmp, sizeof utmp);
                        }
                }
                close (fd);
                sleep (60);
        }
}

Another utmp program was posted to comp.sources.unix, volume 25, issue
96 by David W. Sanderson ([e-mail]) that also works on AIX 3.1.


1.104: How to fsck the root filesystem

You can run fsck either in maintenance mode or on mounted filesystems.
To enter maintenance mode to run fsck on the root filesystem:

  1. boot from diskette
  2. select maintenance mode
  3. type /etc/continue hdisk0 exit (replace hdisk0 with boot disk if
     not hdisk0)
  4. fsck /dev/hd4


1.105: How can I unmount /usr to run fsck on it?
From: [e-mail] (Matt Accapadi)
[ This is for 3.2. ]

In order to fsck /usr, it has to be unmounted. But /usr cannot be
unmounted because /bin is symbolically linked to /usr/bin. Also
/etc/fsck is symbolically linked to /usr/sbin/fsck.

To work around this, when you boot from the boot/maintenance diskettes
and enter maintenance mode, enter "getrootfs hdisk0 sh" instead of
"getrootfs hdisk0" where hdisk0 is the name of the boot disk. Then run
"fsck /dev/hd2".


1.106: How do I shrink /usr?
From: [e-mail] (Michael Stefanik) and Richard Hasting

FOR AIX 3.1
-----------

 1) Make a backup of /usr

        find /usr -print | backup -ivf /dev/rmt0 (or appropriate device)

 2) shutdown to maintenance mode

        shutdown -Fm

 3) export LANG=C

 4) remove the filesystem and the logical volume
    ignore an error about the "dspmsg" command not found

        umount /usr
        rmfs /usr

 5) make a new logical volume hd2 and place it on rootvg with desired size

        mklv -yhd2 -a'e' rootvg NNN

   where NNN is the number of 4 meg partitions

 6) create a filesystem on /dev/hd2

        crfs -vjfs -dhd2 -m'/usr' -Ayes -p'rw'

 7) mount the new /usr filesystem and check it

        /etc/mount /usr
        df -v

 8) restore from the tape; system won't reboot otherwise

        restore -xvf/dev/rmt0

 9) Sync and reboot the system; you now have a smaller /usr filesystem

FOR AIX 3.2
-----------

 1) Remove any unneeded files from /usr.

 2) Make sure all filesystems in the root volume group are mounted. If
    not, they will not be included in the re-installed system.

 3) Type mkszfile. This will create /.fs.size that contains a list of
    the active filesystems in the root volume group that will be
    included in the installation procedure.

 4) Edit .fs.size. Change the size of /usr to what you want.

    Example: This .fs.size file shows /usr to be 40MB.

        rootvg 4 hd2 /usr 10 40 jfs

    The number 10 is the number of physical partitions for the filesystem
    and the 40 is 40 MB. Most systems have a physical partition size of
    4 MB. Therefore, the second number (40) will always be 4 times the
    previous number (10). Note, however, that a model 320 with a 120 MB
    drive will have a physical partition size of only 2 MB, and the
    total MB is twice the number of physical partitions. The first
    number (4) in the .fs.size file represents the PP size.

    If you want to reduce the size of /usr from 40 MB to 32 MB, edit the
    /usr entry to:

        rootvg 4 hd2 /usr 8 32 jfs

    IMPORTANT: Make sure that you DO NOT enter a value which is less
    than the size of the filesystem required to contain the current
    data. Doing so will cause the re-installation procedure to fail.

 5) chdev -l rmt0 -a block=512 -T

 6) Unmount all filesystems that are NOT in the root volume group.

 7) Varyoff all user-defined volume groups, if any

        varyoffvg VGname

 8) Export the user-defined volume groups, if any

        exportvg VGname

 9) With a tape in the tape drive, type

        mksysb /dev/rmt0

     This will do a complete system backup, which will include
     information (in the .fs.size file) for the installation procedure
     on how large the filesystems are to be created.

 10) Follow the instructions in the Installation Kit under "How to
     Install and perform maintenance from Diskettes" using the
     diskettes and tape that you created in the previous steps.
     DO NOT select the option "Reinstall AIX with Current System
     Settings". Instead use "Install AIX with Current System Settings"
     for the logical volume size changes to take affect.

 11) When the installation is complete, you may then import the
     information into your newly installed operating system for any
     user-defined volume groups.

         importvg -y VGname PVname

     where "VGname" is the name of the volume group, and "PVname" is
     the name of any one of the physical volumes in the volume group.

 12) Varyon your user-defined volume groups

         varyonvg VGname

 The reduction of the filesystems is now complete.


1.107: How do I make a filesystem larger than 2 Gig?

The largest filesystem under AIX is 2 Gigabytes because the largest
signed integer is 2**31 - 1.


1.108: How do I see/change system parameters like number of processes
       per user?

You can use SMIT as described below or simply use the lsattr/chdev pair.
The former will list the current setting as in:

  # lsattr -E -l sys0 -a maxuproc
  maxuproc 40 Maximum # of processes allowed per user True

and you can then increase the maxuproc parameter:

  # chdev -l sys0 -a maxuproc=200
  sys0 changed

If you just type 'lsattr -E -l sys0' you will get a list of all
parameters, some of which can be changed but not others.

If you want to use smit, this procedure can be followed:

smit
  System Environments and Processes
    Change / Show Operating System Parameters
      - on this screen you can change by overtyping the following fields:
        - Maximum number of PROCESSES allowed per user
        - Maximum number of pages in block I/O BUFFER CACHE
        - Maximum Kbytes of real memory allowed for MBUFS
      - toggle fields exist for:
        - Automatically REBOOT system after a crash  (false/true)
        - Continuously maintain DISK I/O history (true/false)


1.109: How do I shrink the default paging space on hd6?

1) create a paging space to use temporarily
   mkps -s 20 -a rootvg

2) change default paging space hd6 so it is not used at next reboot
   chps -a n hd6

3) For AIX 3.1, edit /etc/rc.boot4 and change swapon /dev/hd6;
   for AIX 3.2, edit /sbin/rc.boot and change swapon /dev/hd6
   swapon /dev/paging00

4) Update information in boot logical volume
   bosboot -a             (3.1)
   bosboot -a -d hdisk0   (3.2)

5) shutdown and reboot

6) remove current hd6 and create a new one of smaller size
   rmps hd6
   mklv -y hd6 -t paging rootvg <size of PS in 4 Meg blocks>

7) Re-edit /etc/rc.boot4 (3.1), /sbin/rc.boot (3.2) to swap to /dev/hd6
   swapon /dev/hd6

8) Update information in boot logical volume
   bosboot -a             (3.1)
   bosboot -a -d hdisk0   (3.2)

9) change current paging device (paging00) so it is inactive at next boot
   chps -a n /dev/paging00

10) shutdown, reboot, remove paging00 using the command:
    rmps paging00


1.110: The swapper seems to use enormous amounts of paging space, why?

When you run ps, you may see a line like:

USER   PID %CPU %MEM    SZ   RSS     TT STAT  TIME CMD
root     0 0.0%  14% 386528  8688      -    S 17:06 swapper

This is normal behavior, the swapper looks to ps like it has the entire
paging space plus real memory allocated.


1.111: How much paging space do I need?

See answer 2 in question 1.300.


1.112: How do I mount a floppy disk as a filesystem?
From: [e-mail] (Olaf Pors)

You can build a filesystem on a floppy and mount it, however the
filesystem will be read only. The reason that the filesystem will be
read only is because AIX Version 3.1.5 cannot create a journal log on a
diskette. The intended use is for temporary access to read only data.
The diskette file system must be unmounted after use and during system
backup procedures or errors could occur.

To make the read only filesystem on a floppy:

1. Make a subdirectory on an existing filesystem and place all of the
   files that the diskette will contain into this subdirectory.

2. Enter the following command to create a prototype file containing
   information about the new filesystem, in the example /dir_struct
   is the pathname of the subdirectory created in step 1, and
   proto_filename is the name of the prototype file to be created.

         proto /dir_struct > proto_filename

3. Place a formatted floppy into the drive.

4. Edit the prototype file and replace the first line with the following:

         <noboot> 0 0

5. Enter the following command to make the filesystem on your floppy:

          mkfs -p proto_filename -V jfs /dev/fd0

6. Create the directory upon which you will mount the floppy based
   filesystem, or you can use /mnt. Mount the filesystem:

          mount -r -V jfs /dev/fd0 /your_mount_point

7. To unmount the filesystem:

          umount /dev/fd0

Since the filesystem is read-only it may be of limited use but if you
are going to use it for utility programs and other data that does not
change much, it may still be useful. If you need to change the data,
you can copy the directory from the floppy into another directory, make
your modifications, and remake the filesystem using this procedure.


1.113: How do I remove a committed lpp?
From: [e-mail] (Ross Boswell)

This seems to be a common problem. The following script for 3.2 only is
from IBM NZ AIX software support. As far as I know, it works -- I used
it to remove unwanted fonts. I have no official permission to post it
-- use it at your own risk!

#!/bin/ksh
#
# Permanently remove a product from disk and AIX databases
#

if [ `whoami` != "root" ] ; then
  echo You must be root to run this script.
  exit 1
fi

if [ `uname -a | awk '{print $1$4$3}'` != "AIX32" ] ; then
  echo This script only works on AIX 3.2.
  exit 1
fi

TMP_FREE=`df /tmp | awk '$3 ~ /[0-9]/{print $3}'`
if [ "$TMP_FREE" -lt 1000 ] ; then
   echo There is not enough room in your /tmp directory.
   echo You need 1000 KB free, and you have only $TMP_FREE KB free.
   echo Either remove some stuff from /tmp, or use chfs to make it bigger.
   exit 1
fi

ODMDIRS="/etc/objrepos /usr/lib/objrepos /usr/share/lib/objrepos"
ODMDIR=/usr/lib/objrepos
export ODMDIR

if [ $# -lt 1 ]
then
  echo usage: $0 lppname [lppname ...]
  echo lppname is a string compatible with grep, ie "X11" or "PHIGS"
  echo typing   $0 PHIGS   will remove all LPPs with PHIGS in their name.
  exit 1
fi

NAMES=$1
shift
while [ $# -gt 0 ] ; do
  NAMES="$NAMES|$1"
  shift
done
echo "Searching for lpps with egrep \"$NAMES\"...\c"

for ODMDIR in $ODMDIRS ; do
  if [ ! -d $ODMDIR -o ! -w $ODMDIR ] ; then
     echo $ODMDIR is not writeable or is not a directory.
     echo I hope this is because you are a /usr client or diskless.
     echo If you are not a diskless or a /usr client, you should stop.
     echo "Enter y to continue ->\c"
     read answer
     if [ "$answer" != "y" ] ; then
       exit 0
     fi
  fi
  TMP=`odmget lpp | awk -F\" '/name/ {print $2}' | egrep "$NAMES"`
  LPPS=`echo $LPPS $TMP`
done

if [ "$LPPS" = "" ]
then
  echo "failed.\nNo LPP with the name $NAMES detected."
  exit 1
fi
echo ok.

for ODMDIR in $ODMDIRS ; do
  mkdir -p /tmp/rmlpp/$ODMDIR > /dev/null 2>&1
done

> /tmp/listOfFilesToRM$$    # truncate temporary file, just in case.
echo
echo This script is about to attempt to remove an LPP from your system.
echo I say attempt, because it could fail.  If it fails, you may have
echo to at least reload the LPP.  Use the \"lppchk\" command to make sure
echo all is well with your system.
echo
# Loop through all the LPP names found.
for LPP in $LPPS
do
  DESCR=none
  answer=""

  # find the LPP ids.  They will be different in the three SWVPD databases.
  for ODMDIR in $ODMDIRS ; do
    # get the lpp id for this ODMDIR (yes, they are different)
    LPPID=`odmget -q name=$LPP lpp | grep lpp_id | sed 's/.* = //'`

    # did we find the LPP?
    if [ "$DESCR" = "none" -a "$LPPID" != ""  ] ; then
      # all the descriptions should be the same
      DESCR=`odmget -q name=$LPP lpp | grep description | sed 's/.* = //'`
      echo "Delete $LPP, $DESCR?"
      echo "y or (n) ->\c"
      read answer
      if [ "$answer" != "y" ] ; then # jump back up to the next LPP name
        continue 2
      fi
    fi
    # if there is no DESCR, then we didn't find the LPP.  Weird.
    if [ "$DESCR" = "none" -o "$LPPID" = "" ] ; then
      continue
    fi
        SOMETHING_DONE_FLAG=true
    # Optionally, save the ODM stuff we are about to remove,
    # in case something goes wrong.  The problem is it is difficult
    # to determine if something really did fail, since these commands
    # don't return any decent error return codes.
    odmget -q lpp_id=$LPPID history   > /tmp/rmlpp/$ODMDIR/$LPP.history
    odmget -q name=$LPP lpp           > /tmp/rmlpp/$ODMDIR/$LPP.lpp
    odmget -q lpp_name=$LPP product   > /tmp/rmlpp/$ODMDIR/$LPP.product
    # Get the list of files and links to remove later....
    odmget -q lpp_id=$LPPID inventory > /tmp/rmlpp/$ODMDIR/$LPP.inventory
    awk -F\" '/loc/ {print $2}' /tmp/rmlpp/$ODMDIR/$LPP.inventory | \
      sed 's/,/ /g' >> /tmp/listOfFilesToRM$$
    odmdelete -o history -q lpp_id=$LPPID   > /dev/null 2>&1
    odmdelete -o lpp -q name=$LPP           > /dev/null 2>&1
    odmdelete -o product -q lpp_name=$LPP   > /dev/null 2>&1
    odmdelete -o inventory -q lpp_id=$LPPID > /dev/null 2>&1
  done
done

if [ "$SOMETHING_DONE_FLAG" = "true" ] ; then

  echo ODM work is done.  Now, time to delete files....

  # This could be catastrophic if there is a problem.  For example,
  # if the ODM database for an application had / as one of its files.
  # You be the judge.  Here's your rope....
  cat /tmp/listOfFilesToRM$$ | sort -r | uniq | xargs rm -rf

  rm -rf /tmp/listOfFilesToRM$$
  echo done.
fi

# take this line out if you want to save your ODM saved files.
rm -rf /tmp/rmlpp

exit 0


1.114: How can I recover space after installing updates?
From: Milt Cloud <[e-mail]>

Note: If you are a /usr server, do not use this because the files
      mentioned below are needed by /usr clients and cannot be deleted.

Installp creates numerous files in /usr to clean up after
failed/rejected installs and also for de-installing uncommitted lpps.
Once you have COMMITted packages you can remove these files safely.
Depending on your installation activity the numbers can be significant
here: hundreds-to-thousands of files, megabytes of data.

Files eligible for removal are associated with each "product" you have
installed; the largest collection being due to bos.  After
COMMITting bos lpps, you may safely remove all files of the form:

              /usr/lpp/bos/deinstl*
              /usr/lpp/bos/inst_U4*
              /usr/lpp/bosadt/deinstl*
        and   /usr/lpp/bosadt/inst_U4*

You may repeat this for all additional COMMITted products (e.g.,
bostext1, bosnet, xlc) you have on your system.

This problem of lingering install files is a known defect in installp.
If you have installed PTF U411711 (or any superceder of it: U412397,
U413366, U413425) the deadwood in /usr will not be quite as prevalent.
No single PTF currently available completely corrects this problem.

On my own 320, the following freed up 12.4M in /usr:

       # rm -R /usr/lpp/bos/deinstl*
       # rm -R /usr/lpp/bos/inst_U4*


1.115: Where are the AIX log files kept?
From: [e-mail] (Dirk Coldewey)

Such as the equivalent of the SunOS file '/var/log/syslog' and
'/var/adm/messages'.

If you want regular unix syslog files, you can configure syslogd
in /etc/syslog.conf. Here's the one that I use:

#
# See the supplied /etc/syslog.conf file for copious comments.
#
*.err;kern.debug;auth.notice;user.none          /dev/console
*.err;kern.debug;daemon,auth.notice;mail.crit;user.none /var/adm/messages
lpr.debug                                       /var/adm/lpd-errs

*.alert;kern.err;daemon.err;user.none           operator
*.alert;user.none                               root

*.emerg;user.none                               *

# for loghost machines, to have authentication messages (su, login, etc.)
# logged to a file, un-comment out the following line and adjust the
# file name as appropriate.
#
# if a non-loghost machine chooses to have such messages
# sent to the loghost machine, un-comment out the following line.
#
auth.notice                     /var/log/authlog

mail.debug                      /var/log/syslog

# following line for compatibility with old sendmails. they will send
# messages with no facility code, which will be turned into "user" messages
# by the local syslog daemon. only the "loghost" machine needs the following
# line, to cause these old sendmail log messages to be logged in the
# mail syslog file.
#
user.alert                       /var/log/syslog
#
# non-loghost machines will use the following lines to cause "user"
# log messages to be logged locally.
#
user.err                         /dev/console
user.err                         /var/adm/messages
user.alert                       `root, operator'
user.emerg                       *


1.116: How can I log information about ftp accesses to a file?
From: [e-mail] (Ed Ravin) and
      [e-mail] (Michael Page)

1) In /etc/syslog.conf, add the line:
   daemon.debug         /tmp/daemon.log

2) # touch  /tmp/daemon.log
   # refresh -s syslogd

3) Modify your inetd.conf so that ftpd is called with the "-l" flag.
   You may also want the "-d" flag. This can be done with 'smit inetdconf'.

All the syslog messages from various system daemons should now appear in
the file "/tmp/daemon.log".


1.117: How do I find a file name from the inode number?
From: [e-mail] (Kanthan Pillay)

     find /mntpoint -xdev -inum nnnn -print


1.118: How do I set up postscript accounting?
From: [e-mail] (Vince Taluskie)

The following program to configure postscript page accounting was
originally written by Ephraim Vider. It acts as a backend wrapper which
logs accounting information in /etc/qconfig. It can be ftp'd from
utpapa.ph.utexas.edu in /pub/aix/psacct.tar.Z.

To get this program running compile it with

cc  pswrap.c -o pswrap -lqb

and then make this program suid root with

chown root pswrap
chmod u+s pswrap

If this step is not done, the printer will hang.

Then start up SMIT and go to :

Spooler
  Manage Local Printer Subsystem
    Local Printer Queue Devices
      Change / Show Characteristics of a Queue Device
        <Select Queue>
          <Select Device>

and change "BACKEND PROGRAM pathname" to the full pathname of pswrap
since pswrap will now handle the backend interface with the queue.

A stream of info will be written to a logfile in /tmp (prob lp0.log) but
this file is mainly used for status info and raw pagecounts. If the
accounting data is going to the qconfig-specified acctfile, then use the
'pac' command to read it. I prefer to have readable ascii data files
instead, so I just comment out the '#define WANT_PAC' line and it will
only go to the ACCTFILE specfied in pswrap.c.

/*  pswrap.c

 compile with:   cc pswrap.c -o pswrap -lqb
 (for doc on the qb library see "understanding backend routines in libqb")

 BTW:  The log_charge() function doesn't seem to do anything,
       but log_pages() updates the accounting info.

Ephraim Vider, original author

--
Feb 10, 1993

You can set pswrap up to use either the accounting file specified in
/etc/qconfig (which means that you need to get your data from 'pac') or
you can comment out the #define WANT_PAC line and then the accounting
data will only go into the ACCTFILE.

Also modified the logging to the ASCII acctfile so that it looks more
readable.

Vince Taluskie
*/

 #include <stdio.h>
 #include <string.h>
 #include <ctype.h>
 #include <fcntl.h>
 #include <signal.h>
 #include <setjmp.h>
 #include <sys/wait.h>
 #include <IN/backend.h>
 #include <IN/standard.h>
 #include "qprocs.h"

 char     *nextword (char *p);
 char     *skipvalue (char *p);

 #define LOGDIR     "/tmp"
 #define ACCTFILE   "/usr/adm/acct/lpr/ps-acct"
/* #define WANT_PAC     1 */     /* this define will also send accounting
                                 info to the acctfile specified in
                                 /etc/qconfig file.  If this define is
                                 commented out then accounting info will
                                 only go to ACCTFILE  */


 char     pcprog[] = "statusdict begin pagecount = end\n\x04";

 char     *keyw[] = {
     "idle",
     "busy",
     "waiting",
     "printing",
     "initializing",
     NULL
 };
 enum     { PS_IDLE, PS_BUSY, PS_WAIT, PS_PRINT, PS_INIT, PS_UNKNOWN };

 void     giveup();
 jmp_buf  jumper;

 char     logfname[30];
 FILE     *logfile, *acctfile;

 main (argc, argv)
 int argc;
 char     *argv[];
 {
     char *devname;
     int  pagcnt, c;
     int  pid;
     int  w, status;

     if (argc < 2) {
          fprintf(stderr, "Usage: psbe file\n");
          exit(-1);
     }
     if (log_init(argv[1]) < 0) {
          fprintf(stderr, "log_init failed!\n");
          exit(EXITBAD);
     }
     sprintf(logfname, "%s/%s.log", LOGDIR, get_device_name());
     if ((logfile = fopen(logfname, "a")) == NULL) {
          fprintf(stderr, "Can't open logfile.\n");
          exit(EXITBAD);
     }

     if ((acctfile = fopen(ACCTFILE, "a")) == NULL) {
         fprintf(stderr, "Can't open logfile.\n");
         exit(EXITBAD);
         }

     setvbuf(logfile, NULL, _IOLBF, BUFSIZ);
     setvbuf(acctfile, NULL, _IOLBF, BUFSIZ);

     setvbuf(stdin, NULL, _IONBF, 0);
     setvbuf(stdout, NULL, _IONBF, 0);
     fprintf(logfile, "start Job no. %d, queued on %s\n", get_job_number(),
               get_qdate());
     log_status(WAITING);
     pagcnt = getpagecnt();
     log_status(RUNNING);
     if ((pid = fork()) < 0) {
          perror("fork");
          exit(EXITBAD);
     }
     if (pid == 0) {
          argv[0] = "piobe";
          execv("/usr/lpd/piobe", argv);
          perror("exec");
          exit(EXITBAD);
     }
     while ((w = wait(&status)) != pid)
          if (w == -1) {
               perror("wait");
               exit(EXITBAD);
          }
     if (WEXITSTATUS(status) != 0)
          exit(WEXITSTATUS(status));
     log_status(WAITING);

     if (pagcnt > 0 && (c = getpagecnt()) > 0) {
#ifdef WANT_PAC
          log_pages(c - pagcnt);
#endif
        }

     fprintf(logfile, "end Job no. %d, queued on %s\n", get_job_number(),
               get_qdate());

/* the accounting file format is

pages_printed     user     queue_printed_on   time_queued

*/

     fprintf(acctfile, "%d %35s %7s    %s \n", (c - pagcnt), get_from()
 get_queue_name(), get_qdate());

     fclose(logfile);
     fclose(acctfile);
     exit(EXITOK);
 }

 void     giveup ()
 {
     longjmp(jumper, 1);
 }

 getpagecnt ()
 {
     int  pc = 0, pstat;
     char buf[81];

     if (setjmp(jumper) != 0) {
          fprintf(logfile, "giving up on status\n");
          return (0);
     }
     alarm(60 * 2);
     signal(SIGALRM, giveup);
     do {
          if (!gets(buf)) {
               sleep(5);
               putchar('\x14');    /* ^T returns status */
               sleep(1); /* wait for answer from printer */
               if (!gets(buf))
                    return (0);
          }
          fprintf(logfile, "%s\n", buf);
          if ((pstat = getstatus(buf)) == PS_WAIT) {
               putchar('\x04');
               sleep(1);
          }
     } while (pstat != PS_IDLE);
     alarm(0);
     while (gets(buf))
          fprintf(logfile, "%s\n", buf);
     printf("%s", pcprog);
     sleep(1); /* wait for answer from printer */
     if (!gets(buf))
          return (0);
     if (sscanf(buf, "%d", &pc) != 1)
          return (0);
     fprintf(logfile, "%d\n", pc);
     return (pc);
 }

 /*
  * Parser for printer status messages
  */

 getstatus (p)
 char     *p;
 {
     char *t;
     int  i;

     if ((p = strchr(p, '%')) == NULL)
          return (PS_UNKNOWN);
     if (strncmp(p, "%%[", 3) != 0)
          return (PS_UNKNOWN);
     for (p = nextword(p + 3) ; p != NULL ; p = skipvalue(p)) {
          t = p;
          p = strchr(p, ':');
          *p++ = '\0';
          p = nextword(p);
          if (strcmp(t, "status") == 0)
               break;
     }
     if (p == NULL)
          return (PS_UNKNOWN);
     t = p;
     p = strchr(p, ' ');
     if (p[-1] == ';')
          p--;
     *p = '\0';
     for (i = 0 ; keyw[i] != NULL ; i++)
          if (strcmp(t, keyw[i]) == 0)
               break;
     return (i);
 }

 char     *nextword (p)
 char     *p;
 {
     while (isspace(*p))
          p++;
     if (strncmp(p, "]%%", 3) == 0)
          return (NULL);
     return (p);
 }

 char     *skipvalue (p)
 char     *p;
 {
     char *t;

     while (p != NULL) {
          p = strchr(p, ' ');
          t = p;
          p = nextword(p);
          if (t[-1] == ';')
               break;
     }
     return (p);
 }

 /*********    qprocs.h    ***********/
 /* functions for communication between qdaemon and the backend */

 char     *get_from();
 char     *get_to();
 char     *get_qdate();
 char     *get_queue_name();
 char     *get_device_name();
 char     *get_title();


1.119: How do I create boot diskettes for 3.2?

You need to have four formatted diskettes.

boot disk:                bosboot -d /dev/fd0 -a
display disk:             mkdispdskt
display extension disk:   mkextdskt
Install/Maintenance disk: mkinstdskt


1.120: Where can I find tools for performance monitoring?

For 3.2 a few tools are available in /usr/lpp/bosperf. There are tools
to monitor traces, I/O events, CPU, virtual memory, disk block usage,
kernel extensions, etc. It even has a simulator, rmss, that allows one
to try out different memory size configurations to see how it impacts
performance. See 6.05 for the AIX Performance and Tuning Guide.


1.121: How can I tell what virtual printer a print queue is using?
From: [e-mail] (Stuart R. Yoder)

Use the command 'lsvirprt'. Don't use any parameters and it will
run in an interactive mode that will give you a menu of all virtual
printers on the system with the queue and device for each one.


1.122: Two srcmstr's are less useful than one?
From: [e-mail] (Bernhard Zeller)

This can happen on systems that have no console, or systems with an
async terminal as the console but not attached or turned off. One of the
symptoms is a second srcmstr got run. But the second srcmstr is worthless
as we can't use the stop/startsrc commands, refresh inetd, qdaemon won't
start, etc.

To resolve this, type:

    smit chgtty

and add the keyword 'clocal' in following lines:

   STTY attributes for RUN TIME
   STTY attributes for LOGIN


1.123: How do I set the tty name associated with a physical port?
From: [e-mail] (Matt Accapadi)

Let's say you wanted to make a tty on the s1 port and call it rs0000
and a tty on the s2 port and call it rs0001.

You could run:

mkdev -c tty -s rs232 -t tty -l rs0000 -p sa0 -w s1   # creates rs0000
and
mkdev -c tty -s rs232 -t tty -l rs0001 -p sa1 -w s2   # creates rs0001


1.124: How do I use mksysb to clone a system?
From: [e-mail] (Jo Ann Malina)

I use the following steps on the master machine to clone an AIX system:
1) Remove the password from root.
2) Remove the NIS line from the end of the /etc/group file (the last
   line with the +: )
3) Change most of the level '2' designations in /etc/inittab to level
   '3' to prevent them from being started up when the new system is
   booted (the minimum ones to change are rc.nfs and rc.tcpip)
4) Boot in service mode and change the name and ip address to a "spare"
   set to avoid address collision.
5) Clear /tmp, /usr/tmp and /usr/spool/lpd/stat.
6) Run mkszfile and edit it to be sure /usr is as small as possible;
   then mksysb from the command line.

The above changes allow me to boot in normal mode the first time, get in
as root, change the above files back and do the other things necessary
to configure the new system.

Then, of course, I go back and clean up and reboot my master machine.

Note: 1 and 2 lets you log in even if you can't get on the network.
   It prevents the login process from trying to reach an NIS server.
   Step 2 needed only if you use NIS.


1.125: How do I retain timestamps with mksysb?
From: [e-mail] ( Graeme Moffat)

In /usr/lpp/bosinst/bosnet (for net installs), and bosrest (tape), the
'pax' commands all have '-pmop' options.  m = "DON'T retain modification
times".  So, simply change all the '-pmop' to '-pop' and remake
inst/maint diskettes or mksysb tapes.


1.126: How can I find out the machine type?
From: [e-mail] (Sait Umar)

#!/bin/sh
#
#  Author G. Vitillaro              ([e-mail])
#  from an idea of Marc Pawliger    ([e-mail])
#
#  10/12/92  GVT  First (and last) implementation
#
# machine : will get machine type on RISC/6000
#
#
awk '
        BEGIN {
                m["10"]="7013/530 or 7016/730";
                m["11"]="7013/540";
                m["14"]="7013/540";
                m["18"]="7013/530H";
                m["1C"]="7013/550";
                m["20"]="7015/930";
                m["2E"]="7015/950";
                m["2E"]="7015/950E";
                m["30"]="7013/520";
                m["31"]="7012/320";
                m["34"]="7013/520H";
                m["35"]="7012/320H or 320E";
                m["37"]="7012/340";
                m["38"]="7012/350";
                m["41"]="7011/220";
                m["45"]="7011/M20";
                m["5C"]="7013/560";
                m["63"]="7015/970";
                m["64"]="7015/980";
                m["66"]="7015/580";
                m["67"]="7015/570";
                m["75"]="7012/370, 375, or 37T";
                m["76"]="7012/360, 365, or 36T";
                m["77"]="7012/350, 355, or 7013/550L";
                m["78"]="7012/315 or 7013/510 ";
                if ( m[code] != "" )
                        print "This RISC/6000 is a " m[code];
                else
                        print "Unknown Machine";
        }
' code=`uname -m | cut -c9-10` < /dev/null


1.200: Some info about tape backups
From: Craig Anderson

The following supplements the information on rmt devices in
InfoExplorer. It is based on my own personal experience with IBM tape
drives running on AIX 3.1. No warranty is expressed or implied.

CONFIGURING THROUGH SMIT:
    BLOCK size (0=variable length)              (ALL)
        Sets the tape block size.  When reading, the block size must be
        set to the block size set when the tape was written.  When
        using some commands, tapes written with ANY block size can be
        read if the block size is set to 0 (variable length) (see
        "BLOCK SIZES" below).

    Use DEVICE BUFFERS during writes            (ALL)
        Set to yes, the device will buffer data internally on writes.
        This greatly improves performance, but under certain cases may
        be undesirable since the data is not written to tape before
        returning a good indication.

    Use EXTENDED file marks                     (8mm only)
        Extended file marks take up much more space than short (or
        non-extended) file marks.  But extended file marks can be
        overwritten, allowing data not at the beginning of tape to be
        overwritten (see "FILE MARKS" below).

    RETENSION on tape change or reset           (1/4" only)
        If set to "no" then the tape will not be retentioned
        automatically when the tape is inserted.  Note that this will
        take effect only after the device is used.


FILE MARKS:
     Tape devices support multiple tape files.  Tape files are the
     result of a backup/cpio/tar/dd type command, where the device is
     opened, written to, and closed.  Because tapes allow large
     quantities of data to be written on a single tape, several backups
     (that is, tape files), may be combined on one physical tape.
     Between each tape file is a "tape file mark" or simply "file
     mark".  These file marks are used by the device driver to indicate
     where one tape file ends and another begins.

                              B       E
                   <-------   O       O   ------->
                              T       T
              __ ____________________________ _______________
     physical | \            |       |      \             |physical
     beginning|  \           | tape  |       \            | end
       of     |   \          | file  |        \           |  of
      tape    |    \         | mark  |         \          | tape
              |_____\________|_______|__________\_________|

     Note that there is a distinction between the beginning of tape
     (BOT) side of a file mark and the end of tape (EOT) side of a file
     mark.  If the head is on the BOT side of a file- mark, "tctl fsf
     1" command will move only to the EOT side of the same file mark.

     With the 1/4" tape drive, writing can only take place
     sequentially, or after blank tape has been detected.  You cannot
     write over data on the tape (except at BOT).  If you wish to add
     data to a tape which has been written and then rewound you should
     space forward file mark until an error occurs.  Only then can
     you start writing again.

     With an 8mm tape drive, writing can only take place before blank
     tape, an EXTENDED file mark, or at BOT.  Thus if several backups
     have been made on one tape and you wish to overwrite one of the
     backups, position the tape to the place you wish to start writing
     and issue the following commands:
        tctl bsf 1
        tctl eof 1
     The first command skips back to the BOT side of the same file
     mark.  The second command rewrites the file mark (writing is
     allowed before extended file marks).  The erase head will erase
     data ahead of the write head, so that after writing the file mark
     the head will be positioned before blank tape.  Only after this
     may you start writing over data in the middle of the tape.  (All
     data beyond where you are currently writing will be lost).  Note
     that you cannot write over short file marks.  In order for this to
     work, the tape must have been written with extended file marks
     (use smit to change this).

     With the 9-track drive writing can take place anywhere on the
     tape although overwriting single blocks of data is not supported.

     On the 8mm drive extended filemarks use 2.2 megabytes of tape and
     can take up to 8.5 seconds to write.  Short filemarks use 184K
     and take up to 1.5 seconds to write.

BLOCK SIZES:
     When data is written to tape it is written in blocks.  The blocks
     on a tape are separated by inter-record gaps.  It is important to
     understand the structure of the written tape in order to
     understand the problems which can occur with changing block
     sizes.

     In fixed block size mode all blocks on the tape are the same
     size.  They are the size of the block size set in the device
     configuration.  All read()s and write()s to the tape drive must be
     a multiple of the fixed block size.

     In fixed block mode a read() will return as many blocks as needed
     to satisfy the read() request.  If a file mark is encountered
     while reading the tape only the data up until the file mark will
     be returned.

     It is not possible for the tape drive to read a tape whose block
     size is not the same as the block size in the device
     configuration.  (Unless the device configuration is in variable
     size blocks.)

     In variable block size (0) mode, the blocks written on the tape
     are the size of the read() and write() requests to the device
     driver.  In this case, the actual block sizes on the tape can be
     changed using the options to the backup commands (tar -C, cpio -C,
     backup -C).

     In variable mode, read() requests greater than size of the block
     on the tape will return only the data from the next block on the
     tape.  It is this feature that allows tapes written in any block
     size (fixed or variable) to read with the dd command (the output
     from the dd command may be piped to restore, tar, or cpio for
     example.)  Note that backup, tar, and cpio cannot read all tapes
     by using a large block size because they assume there is an error
     if they get a short read().
                dd ibs=128k obs=16k if=/dev/rmt0 | ...

     The tape head is always positioned at an inter-record gap, file
     mark, or blank tape after reading or writing.

     With the 8mm tape drive, using a fixed block size which is not a
     multiple of 1K is inefficient.  The 8mm tape drive always writes
     internally in 1K blocks.  It simulates the effect of variable
     block sizes, but, for example, using a fixed block size of 512
     bytes (or using variable block size and write()ing 512 bytes at a
     time) wastes one half of the tape capacity and gives only one half
     the maximum transfer rate.


EXCHANGING DATA WITH NON-UNIX AND OTHER VENDORS MACHINES:
     Many tape drives support both variable and fixed block sizes.

     Variable block mode writes block sizes the size of the write
     command issued (tar and backup specify this with the -b option).
     In fixed mode, block sizes are fixed and all writes must be a
     multiple of the fixed block size.

     Unix often internally chops larger reads and writes up into
     manageable pieces (often 65535, 65534, or 65532 bytes) before
     doing the actual reads and writes.  This means reads and writes of
     64K bytes are often broken up into a 65535 byte record and a 1
     byte record (In fixed mode the write will fail).  Block sizes >=
     64K (-C128 and greater) should be avoided for this reason.  AIX
     does not break up read and write requests, but be aware of the
     situation on other machines.

     If the tape is written in an unknown block size then set the
     device configuration in smit to use variable size blocks, use the
     "dd" command with a large input block size, and pipe it to the
     restore command.  For example:
          chdev -l rmt0 -a block_size=0
          dd if=/dev/rmt0 ibs=128k obs=16k | tar -tvf-