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Xref: bloom-picayune.mit.edu comp.unix.aix:19918 news.answers:4629 Path: bloom-picayune.mit.edu!enterpoop.mit.edu!news.media.mit.edu!micro-heart-of-gold.mit.edu!xn.ll.mit.edu!ames!sun-barr!cs.utexas.edu!mavrick!basto@cactus.org From: basto@cactus.org (Luis Basto) Newsgroups: comp.unix.aix,news.answers Subject: AIX Frequently Asked Questions (Part 1 of 2) [REPOST] Summary: This posting contains a list of Frequently Asked Questions and their answers about AIX, IBM's version of Unix. Keywords: AIX RS/6000 questions answers Message-ID: <1071@mavrick.UUCP> Date: 16 Dec 92 06:26:56 GMT Expires: 15 Jan 93 01:23:45 GMT Sender: luis@mavrick.UUCP Reply-To: basto@cactus.org (Luis Basto) Followup-To: comp.unix.aix Lines: 1629 Approved: news-answers-request@MIT.Edu Archive-name: aix-faq/part1 Last-modified: Dec 12, 1992 Version: 2.0 Version: $Id: aix.faq,v 2.0 12/12/92 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 it to basto@cactus.org. The list is split into two articles so it can pass thru most mailers. I cannot promise any precise periodic posting but I'll try to post an updated FAQ roughly once a month to comp.unix.aix and to news.answers. Please let your input continue, 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 have not 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. 3.05. 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 really for AIX on the four platforms -- RT, PS/2, 370 and RS/6000, but it has 90% or more of its traffic covering AIX 3.x and the RS/6000. The newsgroups comp.sys.ibm.pc.rt and comp.sys.ibm.ps2.hardware discuss the PC/RT, mostly hardware and AOS 4.3, and on PS/2 hardware respectively. There is no group on AIX for the 370. This article only covers AIX 3.x and the RS/6000, except when specifically noted. If you post questions to comp.unix.aix, please be sure to indicate: - the machine type (not all questions are to the RS/6000) and brief configuration, e.g. 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. ______________________________________________________________________________ Table of contents: 1.00 The AIX operating system - what is it? 1.01 I know neither Unix nor AIX - where do I find more information? 1.02 I am used to Unix systems programming, why should I learn SMIT? 1.03 What is the Object Database? 1.04 How do I get rid of the verbose error messages? 1.05 How do I make an informative prompt in the shell? 1.06 How do I import an /etc/passwd or /etc/group file from another box? 1.07 How do I put my own text into InfoExplorer? 1.08 Who has a termcap/terminfo source for aixterm or the HFT console? 1.09 *Which release of AIX do I have? 1.10 Some known problems, telnet, accounting, who 1.11 Other hints, fsck of /, X-windows and alt-cntl-backspace 1.12 *How do I shrink /usr? 1.13 *How do I shrink the default paging space on hd6? 1.14 *How do I make a filesystem larger than 2 Gig? 1.15 How do I see/change system parameters like number of processes per user? 1.16 My /dev/null seems to have disappeared or become a plain file, why? 1.17 The swapper seems to use extreme amount of paging space, why? 1.18 How much should I trust the ps memory reports? 1.19 *How do I mount a floppy disk as a filesystem? 1.20 *Some info about tape backups 1.21 *How do I do remote backup? 1.22 How do I backup a multi-disk volume group? 1.23 How do I put multiple backups on a single 8mm tape? 1.24 *How do I remove a committed lpp? 1.25 *My named dies frequently, why? 1.26 *How do I trace ethernet packets on an AIX system? 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? 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? 4.00 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 2.3 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 4.18 Expect 5.00 Third party products 5.01 Disk/Tape/SCSI 5.02 Disks 5.03 Memory 5.04 Others 5.05 IBM List of third party products 5.06 *C++ compilers 6.00 Miscellaneous other stuff 6.01 Can I get support by email? 6.02 Some RS232 hints 6.03 VT100 key bindings for aixterm 6.04 What publications are available for AIX and RS/6000? 6.05 Some acronyms 7.00 How do I get this by mailserver or ftp? 7.01 Contributors ______________________________________________________________________________ 1.00: 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 bsdadm file contains useful information if you know BSD and/or SystemV. 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. 1.01: 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. 1.02: 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 also have the possibility of doing 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 to call a large number of specific tools for each part of the system administration. 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. 1.03: What is the Object Database? The Object Database Manager, ODM, stored in /etc/objrepos, is AIX's way of storing all the system management information. Under most circumstances, only SMIT or the commands SMIT call (see above) 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. The very interested user 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. 1.04: 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. 1.05: How do I make an informative prompt in the shell? In the Korn Shell (ksh), the PS1 variable is expanded each time it is printed, so you can use: $ myhost=`hostname` $ PS1='$LOGNAME@$myhost $PWD \$ ' to get, e.g. bengsig@ieibm1 /u/bengsig $ In the C-shell, use: % set myhost=`hostname` % alias cd 'chdir \!*' > /dev/null; set prompt="$LOGNAME@$myhost $cwd % "' % cd to get, e.g. bengsig@dkunix9 /u/bengsig/aixfaq % There is no easy solution in the Bourne Shell. Use the Korn Shell instead. 1.06: How do I import an /etc/passwd or /etc/group file from another box? Make sure that you run usrck and pwdck (/etc/passwd) and grpck (/etc/group) to let AIX work its password/group magic. 1.07: How do I put my own text into InfoExplorer? With AIX 3.1, you cannot do it. AIX 3.2 has a product called InfoCrafter that allows you to do that. 1.08: Who has a termcap/terminfo source for the HFT console? The console used on the RISC System/6000, the PS/2 and the RT can be used as a terminal on another system with the termcap below. You can find this and other termcaps in /lib/libtermcap/termcap.src, including IBM specific ones. The terminfo sources are stored in /usr/lib/terminfo/*.ti. This termcap can also be used from an aixterm window. hf|hft|hft-c|ibm8512|ibm8513|IBM_High_Function_Terminal:\ :co#80:li#25:am:ht:\ :cm=\E[%i%d;%dH:ti=\E[25;1H:te=\E[20h:\ :nd=\E[C:up=\E[A:do=^J:ho=\E[H:\ :bs:sf=\E[S:ec=\E[%dX:\ :cl=\E[H\E[J:cd=\E[J:ce=\E[K:\ :AL=\E[%dL:DL=\E[%dM:al=\E[L:dl=\E[M:\ :im=\E[4h:ei=\E[4l:mi:\ :dm=\E[4h:ed=\E[4l:\ :so=\E[7m:se=\E[m:ul=\E[4m:ue=\E[m:\ :md=\E[1m:mr=\E[7m:mb=\E[5m:me=\E[m:\ :as=^N:ae=^O:sc=\E[s:rc=\E[u:\ :kl=\E[D:kb=^H:kr=\E[C:ku=\E[A:kd=\E[B:kh=\E[H:\ :kn#10:k1=\E[001q:k2=\E[002q:k3=\E[003q:k4=\E[004q:k5=\E[005q:\ :k6=\E[006q:k7=\E[007q:k8=\E[008q:k9=\E[009q:k0=\E[010q:\ :is=\Eb\E[m^O\E[?7h:rs=\Eb\E[m^O\E[?7h\E[H\E[J: 1.09: 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, tells that this is release 3.1.5. (Note that '3' in 3005 has nothing to do with '3' in 3.1.5 - we should stop calling the versions 3005, etc. and call it by its real version number 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. Here is a description on IBM's release numbering scheme: From: jswillia@nycvmic2.vnet.ibm.com The output of lslpp -h bos.obj shows a release number similar to 03.01.0002.0003. Contrary to your description and some other news items, this should be referred to as 3.1.2 not 3002. The 3002 numbering is used to indicate a PTF update tape. There are two types of PTF tapes 300x and 200x. The 300x tapes are full PTF's to update all previous levels to 3.1.x level The 200x tapes are incremental tapes and only apply to level 3.1.(x-1), ie 2004 updates 3.1.3 to 3.1.4 and will not work with 3.1.2 at all, whereas 3004 would update 3.1.0, 3.1.1, 3.1.2, and 3.1.3 upto level 3.1.4. The release number is defined as follows, 03.01 is the major release number shortened to 3.1 and the 0002 in the example is the minor release number. Major releases are provided with full installable tapes, whereas minor releases are obtained by applying a PTF update tape to a previous level as indicated above. The fourth number is used by development and has no validity(?) outside of development ( note it may be of interest during defect resolution ). For AIX 3.2, it's a completely different scheme. You may come across discussions on releases 3.2.0, 3.2.1, 3.2.2, or 3.2.3. 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. And since one can apply selective fixes it is possible that there could be many slightly different variations of 3.2 in use. IBM is currently working on resolving this situation. 1.10: Some known problems, telnet, accounting, who There are known problems in telnetd in 3.1.2 and 3.1.3 (the RS/6000 may lock when telnet'ing to it, use the 3001 telnetd or update to 3.1.5), accounting has a number of problems, and 'who' often displays entries that do not correspond to active sessions. Following refers to 3.1.2 and 3.1.3. The problem with telnetd seems to be solved in 3.1.5, I do not know about accounting, but the problem with who is known not to be solved. The program below by jfh@rpp386.cactus.org (John F. Haugh) can be used to fix up your /etc/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 (dws@cs.wisc.edu) that also works on AIX 3.1. 1.11: Other hints, fsck of /, X-windows and cntl-alt-backspace - Normally cntl-alt-backspace will kill the X session. If you add the -T option when initializing X, this will not happen. - You should never run fsck on mounted filesystems; you need to be in 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 1.12: How do I shrink /usr? From: mike@bria.UUCP (Michael Stefanik) and Richard Hasting FOR AIX 3.1 ----------- 1) Make a backup of /usr find /usr -print | backup -ivf /dev/rmt0 Use the appropriate tape device if it is not rmt0. 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 therefore 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" during the install procedure. The new system must be installed using the option "Install AIX with Current System Settings" for the logical volume size changes to take affect. 11) When the operating system 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. 1.13: 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 1.14 *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**32 - 1. 1.15: 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 - others not. 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) 1.16: My /dev/null seems to have disappeared or become a plain file, why? The script /usr/etc/lsnfsexp has a bug in 3.1.3. Change line 100 from rm -rf ${TMP_FILE} >/dev/null 2>&1 /dev/null to rm -rf ${TMP_FILE} >/dev/null 2>&1 and recreate /dev/null by: # mknod /dev/null c 2 2 # chmod 666 /dev/null This is fixed in release 3.1.5. 1.17: The swapper seems to use extreme amount 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. 1.18: How much should I trust the ps memory reports? From: chukran@austin.VNET.IBM.COM Using "ps vg" gives a per process tally of memory usage for each running process. Several fields give memory usage in different units, but these numbers do not tell the whole story on where all the memory goes. First of all, the man page for ps does not give an accurate description of the memory related fields. Here is a better description: RSS - This tells how much RAM resident memory is currently being used for the text and data segments for a particular process in units of kilobytes. (this value will always be a multiple of 4 since memory is allocated in 4 KB pages). %MEM - This is the fraction of RSS divided by the total size of RAM for a particular process. Since RSS is some subset of the total resident memory usage for a process, the %MEM value will also be lower than actual. TRS - This tells how much RAM resident memory is currently being used for the text segment for a particular process in units of kilobytes. This will always be less than or equal to RSS. SIZE - This tells how much paging space is allocated for this process for the text and data segments in units of kilobytes. If the executable file is on a local filesystem, the page space usage for text is zero. If the executable is on an NFS filesystem, the page space usage will be nonzero. This number may be greater than RSS, or it may not, depending on how much of the process is paged in. The reason RSS can be larger is that RSS counts text whereas SIZE does not. TSIZ - This field is absolutely bogus because it is not a multiple of 4 and does not correlate to any of the other fields. These fields only report on a process text and data segments. Segment size which cannot be interrogated at this time are: Text portion of shared libraries (segment 13) Files that are in use. Open files are cached in memory as individual segments. The traditional kernel cache buffer scheme is not used in AIX 3. Shared data segments created with shmat. Kernel segments such as kernel segment 0, kernel extension segments, and virtual memory management segments. Speaking of kernel segments, the %MEM and RSS report for process zero are totally bogus for AIX 3.1. The reason why RSS is so big is that the kernel segment zero is counted twice. For AIX 3.2, this has been changed, but the whole story is still not known. The RSS value for process 0 will report a very small number of the swapper private data segment. It does not report the size of the kernel segment 0, where the swapper code lives. In summary, ps is not a very good tool to measure system memory usage. It can give you some idea where some of the memory goes, but it leaves too many questions unanswered about the total usage. 1.19 *How do I mount a floppy disk as a filesystem? From: op@holmes.acc.Virginia.EDU (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 the 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 on the hardfile, 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 your floppy disk into the drive and format it. 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 the /mnt directory. Enter the following command to mount the filesystem: mount -r -V jfs /dev/fd0 /your_mount_point 7. To unmount the filesystem, use the command: 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 still may 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. 1.20 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- 1.21: *How do I do remote backup? From: oquinn@elder.austin.ibm.com You can back up files on a remote tape drive with: tar -cBf - . | rsh REMOTEHOST "tar -xBf /dev/TAPEDEVICE" From: kraemerf@franvm3.VNET.IBM.COM (Frank Kraemer) mksysb will not back up to remote tape devices. Frank provided the following script to do remote backups. #!/bin/ksh # @(#) Create a backup tape of the private user data. #=================================================================# # Script : usave.sh # # Author : F. Kraemer # # Date : 92/02/19 # # Update : 92/10/29 # # Info : the ultimative backup script # # Example: usave.sh /dev/rmt0 - save to local tape # # usave.sh /save/save.me - save to local file # # usave.sh /tmp/pipe - save to remote tape # #-----------------------------------------------------------------# PS4="(+) " #set -x PROG=$(basename $0) HOST=$(hostname) TODAY=$(date +%H:%M:%S) #-----------------------------------------------------------------# # cleanup # #-----------------------------------------------------------------# cleanup () { ec=$1 error=$2 case "$ec" in "$USAGE_EC") # usage error error="Usage:\t$PROG DeviceName\n" 1>&2 ;; "$NOTAP_EC") # Tape error error="error:\t$PROG: $DEVICE is not available on the system.\n" 1>&2 ;; "$LISTE_EC") # list error error="error:\t$PROG: could not create tar list for $LOGNAME.\n" 1>&2 ;; "$NOTAR_EC") # tar command error error="error:\t$PROG: tar command failed.\n" 1>&2 ;; "$PIPEP_EC") # pipe error error="error:\t$PROG: mknod command failed.\n" 1>&2 ;; "$NORSH_EC") # rsh error error="error:\t$PROG: rsh - Remote Shell command failed.\n" 1>&2 ;; "$RHOST_EC") # remote host error error="error:\t$PROG: Remote Host unknown.\n" 1>&2 ;; *) ;; esac case "$DEVICE" in # # Fix the block size if $DEVICE is a tape device # /dev/rmt[0-9]*) echo "\n\t$PROG: Rewinding tape to begin.........(please wait)\n" tctl -f $DEVICE rewind 2>/dev/null ;; *) ;; esac rm -f ${LIST} ${PIPE} 2>/dev/null [ -n "$error" ] && echo "\n${error}\n" trap '' 0 1 2 15 exit "$ec" } #-----------------------------------------------------------------# # Variables. # #-----------------------------------------------------------------# USAGE_EC=1 # exit code for usage error NOMNT_EC=2 # exit code wrong device name NOTAP_EC=3 # exit code no tape available LISTE_EC=4 # exit code backup list error NOTAR_EC=5 # exit code for wrong tar TRAPP_EC=6 # exit code for trap PIPEP_EC=7 # exit code for pipe RHOST_EC=8 # exit code for bad ping NORSH_EC=9 # exit code for bad rsh DEVICE="$1" # device to tar into LIST="/tmp/.tar.$LOGNAME.$$" # REMOTEH="" # Remote host for backup REMOTET="" # Remote tape for backup tapedev= # PIPE="/tmp/pipe" # Pipe for remote backup #-----------------------------------------------------------------# # main() # #-----------------------------------------------------------------# tput clear echo "\n\t$PROG started from $LOGNAME@$HOST on $TERM at $TODAY.\n" rm -f $LIST 2>/dev/null #-----------------------------------------------------------------# # Trap on exit/interrupt/break to clean up # #-----------------------------------------------------------------# trap "cleanup $TRAPP_EC \"Abnormal program termination. $PROG"\" 0 1 2 15 #-----------------------------------------------------------------# # Check command options # #-----------------------------------------------------------------# [ "$#" -ne 1 ] && cleanup "$USAGE_EC" "" #-----------------------------------------------------------------# # Check device name # #-----------------------------------------------------------------# [ `expr "$DEVICE" : "[/]"` -eq 0 ] && cleanup "$NOMNT_EC" \ "$PROG: Backup device or file name must start with a '/'." #-----------------------------------------------------------------# # Check tape device. # #-----------------------------------------------------------------# case "$DEVICE" in # # Fix the block size if $DEVICE is a tape device # /dev/rmt[0-9]*) # echo "\n\t$PROG: Verify backup media ($DEVICE)............\n" # # see if a low or high density tape device was specified # (eg rmt0.1) density="`expr $DEVICE : \ "/dev/rmt[0-9]*\.$[0-9]*$"`" # # strip /dev/ from device name and # get the base name (eg translate: # /dev/rmt0.2 to rmt0) # tapedev="`expr $DEVICE : \ "/dev/$rmt[0-9]*$[\.]*[0-9]*"`" # # Check if the tape is defined in the system. lsdev -C -c tape -S Available -F "name" | grep $tapedev >/dev/null 2>&1 rc=$? [ "$rc" -ne 0 ] && cleanup "$NOTAP_EC" "" # # Restore old tape name. # [ "${density:-1}" -lt 4 ] && density=1 || density=5 DEVICE="/dev/${tapedev}.${density}" echo "\n\t$PROG: Insert a tape in ($DEVICE)........(press enter)\n" read TEMP echo "\n\t$PROG: Rewinding tape to begin...........(please wait)\n" tctl -f $DEVICE rewind 2>/dev/null ;; # # Backup is done on remote host. The remote shell facility # must be set up and running. # ${PIPE}*) # echo "\n\t$PROG: Assuming remote backup via network.\n" echo "\t$PROG: Enter name of Remote Host ===> \c" read REMOTEH echo "\n\t$PROG: Pinging Remote Host to test connection.\n" ping ${REMOTEH} 1 1 >/dev/null 2>&1 rc=$? # give up unknown host [ "$rc" -ne 0 ] && cleanup "$RHOST_EC" "" JUNK=$(rsh ${REMOTEH} "/usr/sbin/lsdev -C -c tape -S Available") rc=$? # give up rsh failed [ "$rc" -ne 0 ] && cleanup "$NORSH_EC" "" echo "\t$PROG: Available Tapes on ${REMOTEH} are :\n\n\t\t${JUNK}\n" echo "\t$PROG: Enter name of Remote Tape (e.g. /dev/rmt0) ===> \c" read REMOTET echo "\n\t$PROG: Insert tape on ${REMOTEH} in ${REMOTET}..(press enter)" read TEMP echo "\t$PROG: Rewinding Remote Tape ${REMOTET} on ${REMOTEH}.\n" rsh ${REMOTEH} "tctl -f ${REMOTET} rewind" rc=$? # give up rsh failed [ "$rc" -ne 0 ] && cleanup "$NOTAP_EC" "" rm -f ${PIPE} 2>/dev/null mknod ${PIPE} p rc=$? # give up mknod failed [ "$rc" -ne 0 ] && cleanup "$PIPEP_EC" "" cat ${DEVICE} | rsh ${REMOTEH} "dd of=${REMOTET} obs=100b 2>/dev/null" & ;; *) ;; esac #-----------------------------------------------------------------# # Prepare the list. # #-----------------------------------------------------------------# echo "\n\t$PROG: Create list of files to be saved...." find $HOME -print > $LIST rc=$? [ "$rc" -ne 0 ] && cleanup "$LISTE_EC" "" #-----------------------------------------------------------------# # tar the files. # #-----------------------------------------------------------------# echo "\n\t$PROG: Changing current directory to (/)...." cd / > /dev/null 2>&1 echo "\n\t$PROG: Running tar format backup from user ($LOGNAME)...." tar -cvf "$DEVICE" -L "$LIST" rc="$?" [ "$rc" -ne 0 ] && cleanup "$NOTAR_EC" "" #-----------------------------------------------------------------# # Backup completed # #-----------------------------------------------------------------# TODAY=$(date +%H:%M:%S) echo "\n\t$PROG ended at $TODAY............................\n\n" cleanup 0 #-----------------------------------------------------------------# # EOF # #-----------------------------------------------------------------# 1.22: How do I backup a multi-disk volume group? From: pack@acd.ucar.edu (Daniel Packman) [ Editor's note: I have not verified this procedure. I would actually recommend NOT to have one volume group span multiple disks unless you really need such big logical volumes. ] 1. If you have a set of three or more disks in a volume group. (typically 3 for 5xx machines with three internal drives; with only two, the procedures outlined here have to be modified to ignore the fact that you don't have a quorum in the volume group) 2. If one drive has failed (usually only one fails at a time :-) ) It is possible to go through a service boot and (if we say the volume group is called rootvg and one of the 2 good disks on it is called hdisk0): importvg -y rootvg hdisk0 varyonvg -f -n -m1 rootvg These commands will work, but give error messages. If you wish to mount a user filesystem, say /u on logical volume /dev/lv00, then mount -f /dev/lv00 /v will work only if the jfslog, the journaled file system log device, is not on the damaged disk. If it is, you must (and can in any case) mount the filesystem read-only: mount -f -r /dev/lv00 /v This crucial and rather obvious point baffled several level 3 support personnel at Austin as well as myself for almost a week. Once the file system(s) of interest are available, then they can be saved to tape for restoration later. Of course, one can expect only about two thirds of a filesystem to be recoverable if it spans all 3 physical disks. One other point to remember is that the standard boot procedure from floppy includes the restore command but does not include the backup command. ****************************************************************************** * If you do not have other RS6000 machines at your site is is imperative * * that you either build a bootable tape which includes either restore or * * tar or cpio (a bootable floppy set will not have enough space) or at the * * very least copy onto a spare floppy backup, cpio, or tar. The floppy * * should be created with backup -ivq so that its contents can be read into * * the memory resident system after booting. * ****************************************************************************** All is not lost if tar, cpio or backup are available on an undamaged disk that can be mounted. Since tar and cpio are in /bin, they may both very well be unavailable. It is a very good idea for those who have tape devices to build a bootable tape with their desired extra commands in it. Follow the instructions from IBM but add your desired commands to the following three files: /usr/lpp/bosinst/tape2 /usr/lpp/bosinst/diskette/boot2 /usr/lpp/bosinst/diskette/inslist If you have anything other than a minimum memory configuration, you should be able to add many commands. 1.23: How do I put multiple backups on a single 8mm tape? From: kerm@mcnc.org (Cary E. Burnette) There are two possible solutions to this, which both use the /dev/rmt0.1 device which is non-rewinding. SOLUTION #1 ----------- To put multiple backups on a single tape, use /dev/rmt0.1, which is a no-rewind device, using either rdump or backup (both by name & inode work). Using rdump or backup "byinode" both generate the message that the tape is rewinding but actually do not. This is an example that would work on my system: # rsh remote1 -l root /etc/rdump host:/dev/rmt0.1 -Level -u /u # rsh remote2 -l root /etc/rdump host:/dev/rmt0.1 -Level -u /u # tctl -f /dev/rmt0.1 rewind # rewinds the tape where I am implementing the command from host. To restore a table of contents of the first I would use # restore -f /dev/rmt0.1 -s1 -tv where the -s1 flag tells restore to go to the first record it comes across on the tape. To get the second type in exactly the same once again. Basically -s(Number) stands for - go to Number record from this spot. It works pretty well. SOLUTION #2 ----------- Steve Knodle Educational Resources Center Clarkson University I use: ------------------- Dump.sh -------------------- CONTENTSFILE=`date |dd conv=lcase |sed -e 's/19//' |awk '{print $6 $2 $3}'` set -x LEVEL=$1 shift backup -c -b 56 -$LEVEL -uf /dev/rmt0.1 / backup -c -b 56 -$LEVEL -uf /dev/rmt0.1 /usr backup -c -b 56 -$LEVEL -uf /dev/rmt0.1 /u tctl -f /dev/rmt0 rewind touch /usr/local/dumps/Contents.$CONTENTSFILE echo "Dumping /" >>/usr/local/dumps/Contents.$CONTENTSFILE restore -t -s 1 -f /dev/rmt0.1 >>/usr/local/dumps/Contents.$CONTENTSFILE echo "Dumping /usr" >>/usr/local/dumps/Contents.$CONTENTSFILE restore -t -q -s 1 -f /dev/rmt0.1 >>/usr/local/dumps/Contents.$CONTENTSFILE echo "Dumping /u" >>/usr/local/dumps/Contents.$CONTENTSFILE restore -t -q -s 1 -f /dev/rmt0.1 >>/usr/local/dumps/Contents.$CONTENTSFILE tctl -f /dev/rmt0 rewind I process the table-of-contents first by a little program that does common prefix encoding, and then compress. This gives a table of contents file I can keep on-line until the tape is reused. 1.24 *How do I remove a committed lpp? From: drb@chmeds.ac.nz (Ross Boswell) This seems to be a common problem. I got the following script 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 1.25 *My named dies frequently, why? Running on 3.2, named dies frequently on network's primary name server. From: jpe@ee.egr.duke.edu (John P. Eisenmenger) Try the following: stopsrc -s named # stop running named setenv MALLOCTYPE 3.1 # use 3.1 memory allocation algorithm /etc/named ... # don't use smit to start named You might be able to use startsrc/smit after setting MALLOCTYPE and get the same effect, but I'm not sure. [According to John, the problem is malloc() in the named code. He also suggests using Berkeley's bind, which he has ported and can be ftp'ed from ftp.egr.duke.edu, /archives/network/bind-4.8.3.tar.Z. -ed] 1.26: How do I trace ethernet packets on an AIX system? From: afx@muc.ibm.de (Andreas Siegert) Do the following: iptrace -i en0 /tmp/ipt The iptrace backgrounds. Find its process id and kill it when you are ready. Then run ipreport -rns /tmp/ipt >/tmp/ipr and look at the output. The current version of Info does not document the r, n and s options but they are quite useful for layering the output. ______________________________________________________________________________ 2.00: C/C++ Contrary to many people's belief, the C environment on the RS/6000 is not very special. The C compiler has quite a number of options that can be used to control how it works, which "dialect" of C it compiles, how it interprets certain language constructs, etc. InfoExplorer includes a Users' Guide and a Reference Manual. The compiler can be invoked with either xlc to invoke it in ANSI mode and cc to invoke it in RT (i.e. IBM 6150 with AIX 2) compatible mode. The default options for each mode are set in the /etc/xlc.cfg file, and you can actually add another stanza and create a link to the /bin/xlc executable. The file /usr/lpp/xlc/bin/README.xlc has information about the C compiler, and the file /usr/lpp/bos/bsdport contains useful information, in particular for users used to BSD. The file /etc/xlc.cfg also shows the symbol _IBMR2 that is predefined, and therefore can be used for #ifdef'ing RS/6000 specific code. 2.01: I cannot make alloca work A famous routine, in particular in GNU context, is the allocation routine alloca(). Alloca allocates memory in such a way that it is automatically free'd when the block is exited. Most implementations does this by adjusting the stack pointer. Since not all C environments can support it, its use is discouraged, but it is included in the xlc compiler. In order to make the compiler aware that you intend to use alloca, you must put the line #pragma alloca before any other statements in the C source module(s) where alloca is called. If you don't do this, xlc will not recognize alloca as anything special, and you will get errors during linking. In earlier releases of the C compiler, alloca did not work well with the optimizer turned on (-O flag), but this problem is solved now. The fix was probably in release 1.1.3 of xlc.obj, it is for sure in 1.1.5. 2.02: How do I compile my BSD programs? The file /usr/lpp/bos/bsdport contains information on how to port programs written for BSD to AIX 3.1. The contents of this file can actually be very useful for others as well. A quick cc command for most "standard" BSD programs is: $ cc -D_BSD -D_BSD_INCLUDES -o [loadfile] [sourcefile.c] -lbsd If your software has system calls predefined with no prototype parameters, also use the -D_NO_PROTO flag. 2.03: Isn't the linker different from what I am used to? Yes. It is not at all like what you are used to: - The order of objects and libraries is normally _not_ important. The linker reads _all_ objects including those from libraries into memory and does the actual linking in one go. Even if you need to put a library of your own twice on the ld command line on other systems, it is not needed on the RS/6000 - doing so will even make your linking slower. - One of the features of the linker is that it will replace an object in an executable with a new version of the same object: $ cc -o prog prog1.o prog2.o prog3.o # make prog $ cc -c prog2.c # recompile prog2.c $ cc -o prog.new prog2.o prog # make prog.new from prog # by replacing prog2.o - The standard C library /lib/libc.a is linked shared, which means that the actual code is not linked into your program, but is loaded only once and linked dynamically during loading of your program. - The ld program actually calls the binder in /usr/lib/bind, and you can give ld special options to get details about the invocation of the binder. These are found on the ld man page or in InfoExplorer. - If your program normally links using a number of libraries (.a files), you can 'prelink' each of these into an object, which will make your final linking faster. E.g. do: $ cc -c prog1.c prog2.c prog3.c $ ar cv libprog.a prog1.o prog2.o prog3.o $ ld -r -o libprog.o libprog.a $ cc -o someprog someprog.c libprog.o This will solve all internal references between prog1.o, prog2.o and prog3.o and save this in libprog.o Then using libprog.o to link your program instead of libprog.a will increase linking speed, and even if someprog.c only uses, say prog1.o and prog2.o, only those two modules will be in your final program. This is also due to the fact that the binder can handle single objects inside one object module as noted above. If you are using an -lprog option (for libprog.a) above, and still want to be able to do so, you should name the prelinked object with a standard library name, e.g. libprogP.a (P identifying a prelinked object), that can be specified by -lprogP. You cannot use the archiver (ar) on such an object. You should also have a look at section 3.01 of this article, in particular if you have mixed Fortran/C programs. 2.04: How do I link my program with a non-shared /lib/libc.a? cc -o prog -bnoso -bI:/lib/syscalls.exp obj1.o obj2.o obj3.o will do that for a program consisting of the three objects obj1.o, etc. 2.05: How do I make my own shared library? To make your own shared object or library of shared objects, you should know that a shared object cannot have undefined symbols. Thus, if your code uses any externals from /lib/libc.a, the latter MUST be linked with your code to make a shared object. Likewise, you cannot split your code into more than one shared object if externals in one object refer to another one. Assume you have one file, sub1.c, containing a routine with no external references, and another one, sub2.c, calling stuff in /lib/libc.a. You will also need two export files, sub1.exp, sub2.exp. Read the example below together with the examples on the ld man page. ---- sub1.c ---------------------------------------------------------- int addint(int a, int b) { return a + b; } ---- sub2.c ---------------------------------------------------------- #include <stdio.h> void printint(int a) { printf("The integer is: %d\n", a); } ---- sub1.exp ---------------------------------------------------------- #! addint ---- sub2.exp ---------------------------------------------------------- #! printint ---- usesub.c ---------------------------------------------------------- main() { printint( addint(5,8) ); } --------------------------------------------------------------- The following commands will build your libshr.a, and compile/link the program usesub to use it. Note that you need the ld option -lc for sub2shr.o since it calls printf from /lib/libc.a. $ cc -c sub1.c $ ld -o sub1shr.o sub1.o -bE:sub1.exp -bM:SRE -T512 -H512 $ cc -c sub2.c $ ld -o sub2shr.o sub2.o -bE:sub2.exp -bM:SRE -T512 -H512 -lc $ ar r libshr.a sub1shr.o sub2shr.o $ cc -o usesub usesub.c -L: libshr.a $ usesub The integer is: 13 $ 2.06: Linking my program fails with strange errors. Why? Very simple, the linker (actually called the binder), cannot get the memory it needs, either because your ulimits are too low or because you don't have sufficient paging space. Since the linker is quite different from normal Unix linkers and actually does much more than these, it also uses a lot of virtual memory. It is not unusual to need 10000 pages (of 4k) or more to execute a fairly complex linking. If you get 'BUMP error', either ulimits or paging is too low, if you get 'Binder killed by signal 9' your paging is too low. First, check your memory and data ulimits; in korn shell 'ulimit -a' will show all limits and 'ulimit -m 99999' and 'ulimit -d 99999' will increase the maximum memory and data respectively to some high values. If this was not your problem, you don't have enough paging space. If you will or can not increase your paging space, you could try this: - Do you duplicate libraries on the ld command line? That is never necessary. - Do more users link simultaneously? Try having only one linking going on at any time. - Do a partwise linking, i.e. you link some objects/libraries with the -r option to allow the temporary output to have unresolved references, then link with the rest of your objects/libraries. This can be split up as much as you want, and will make each step use less virtual memory. If you follow this scheme, only adding one object or archive at a time, you will actually emulate the behavior of other Unix linkers. If you decide to add more paging space, you should consider adding a new paging space on a second hard disk, as opposed to just increasing the existing one. Doing the latter could make you run out of free space on your first harddisk. It is more involved to shrink a paging space but easier to delete one. -- Luis Basto Computer Sciences Corporation Internet: basto@cactus.org Usenet: cs.utexas.edu!mavrick!luis