AIX Interview question : PART 1

IBM has announced "AIX5L".  It's essentialy AIX Version 5.  The 'L' stands
for "Linux Affinity".  A statement that AIX is going to support some of the
Linux API's and interfaces (for instance: the /proc filesystem)

Some changes to the filesystem limits, virtual IP's, dynamic dealocation
of swapspaces.

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.

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

If the other box is non-AIX,  copy the password and group entries for
the non-system users into AIX's /etc/passwd and /etc/group files.
Then run /bin/pwdck -t ALL.  This will create the proper entries in
the shadow password file (/etc/security/users).  You should also run
usrck and grpck.

To duplicate the password and  group entries from another AIX box,
copy /etc/passwd, /etc/group, /etc/security/passwd, /etc/security/group,
/etc/security/user, /etc/security/limits, /etc/security/environ.  The
last three are optional unless you modified them.  If you modified
/etc/security/login.cfg, you should also copy that file.
How to fsck the root filesystem

You can run fsck either in maintenance mode or on mounted filesystems.
Try this:

  1. boot from diskette (AIX 3 only --- AIX 4 boot from CD or tape)
  2. select maintenance mode
  3. type /etc/continue hdisk0 exit (replace hdisk0 with boot disk if
     not hdisk0)
  4. fsck /dev/hd4
How can I unmount /usr to run fsck on it?

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".

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

You can use SMIT as described below or simply use lsattr/chdev.
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, do as follows:

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)
How do I shrink the default paging space on hd6?

create a paging space to use temporarily
   mkps -s 20 -a rootvg
change default paging space hd6 so it is not used at next reboot
   chps -a n hd6
swapon /dev/paging00
sysdumpdev -p /dev/paging00
Update information in boot logical volume

   bosboot -ad /dev/hdisk0 
reboot
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>
swapon /dev/hd6
change the dump device back to hd6:

   sysdumpdev -p /dev/hd6
Update information in boot logical volume

   bosboot -ad hdisk0
change current paging device (paging00) so it is inactive at next boot
   chps -a n /dev/paging00
shutdown, reboot, remove paging00 using the command:
    rmps paging00
You can check your paging space with `lsps -a`
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.
How do I remove a committed lpp?

installp has a new option, uninstall (-u) which can be used to remove lpps.  BEWARE of pre-requisite chains.
How can I recover space after installing updates?

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: 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 superseder 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*
Where are the AIX log files kept?
AIX logs messages as specified in /etc/syslog.conf.  Here's an
example

#
*.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                       *
How can I log information about ftp accesses to a file?

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".

How do I find a file name from the inode number?

ncheck -i nnnn /mntpoint