Unix Articles & FAQ

From IBM, replace /var with /usr, of course:

How to reduce the /var or /tmp filesystem

The following steps reduce the size of the
/var or /tmp file system in all supported releases
 of AIX Versions 4 and 5. If either file system
on your machine is 8192KB in size or smaller, you
 probably should not reduce it. The default size of
the /var file system(on installation) is 4096KB,
which fills up rather quickly.If you can afford the
 space, it is better to have /var be 8192KB total.
The default size of the /tmp file system (upon installation)
is 8192KB.

NOTE: Back up the data before proceeding. If you have a
tape drive connected to your system, this can
 be achieved
by executing the following sequence of commands
on either /var or /tmp:

    cd /
    tar -cvf /dev/rmt0 /var

/dev/rmt0 can be replaced with /dev/fd0 or the full path of
a directory NOT in the same file system.


Boot your system into a limited function maintenance shell
(Service or Maintenance mode) from bootable
AIX media.

Please refer to your system's user's or installation and service
 guide for specific IPL procedures related
to the type and model of your system. Additionally,
the document titled "Booting in Service Mode", has specific
 procedures for most types of systems. The document
is available at this location:

http://techsupport.services.ibm.com/rs6k/techbrowse


With bootable media of the same version and level as the
 system, boot the system into Service mode.
The bootable media can be any ONE of the following:

Bootable CD-ROM
NON_AUTOINSTALL, bootable mksysb
Bootable Install Tape
Follow the screen prompts or icons to the Welcome to Base OS menu.


Choose Start Maintenance Mode for System Recovery (Option 3). The next
screen displays prompts for the
Maintenance menu.

Choose Access a Root Volume Group (Option 1).
The next screen displays a warning that indicates you will not be able
to return to the Base OS menu without
rebooting.


Choose 0 continue.
The next screen displays information about all volume groups on the system.


Select the root volume group by number. The logical volumes in rootvg will
be displayed with two options.

Choose Access this volume group and start a shell. (Option 1).
If you get errors from the preceding option, do not continue with this
procedure. Correct the problem causing the error.
 If you need assistance correcting the problem causing the error, contact
one of the following:

Local branch office
Your point of sale
Your AIX support center
If no errors occur, proceed with the following steps.


Unmount the file system. (The following examples use /var.
If you intend to reduce the /tmp file system, substitute /tmp
for /var in the commands.) Execute:
    umount /var

Remove the file system by executing:
    rmfs /var


Determine the physical partition (PP) size of your rootvg
volume group with the command:
   lsvg rootvg

Create the logical volume with one of these commands:
    mklv -y hd9var rootvg [x]     (for /var)
    mklv -y hd3 rootvg [x]           (for /tmp)

where x is the number of logical partitions you want to allocate.
If your
rootvg volume group has a PP size of 4MB, and you want the
total size of the /var file system to be 8MB, then x would be 2.
 For example:

    mklv -y hd9var rootvg 2

This command makes a logical volume hd9var of size 8MB (two 4MB partitions)
 in the rootvg volume group.

NOTE:The logical volume name used for the /tmp file system is
hd3, and hd9var is the logical volume name used for /var.
These names must be used if you wish to maintain your AIX system
in an IBM supported state.
 

Create the file system with the following command:
    crfs -v jfs -d hd9var -m /var -a check=false -a free=false -a vol=/var


NOTE: Substitute hd3 for hd9var and /tmp for /var if needed. Refer to the section
Example of /etc/filesystems for the different attributes required for these filesystems.


Mount the file system:
    mount /var        (OR    mount /tmp)

If you are recreating /var, now create the /var/tmp directory for the vi editor. Execute:
    mkdir /var/tmp

Set your TERM variable and export it. If you are using a megapel display,
 try setting TERM=hft. If you are using an ASCII terminal such as an IBM 3151,
 set your TERM to the appropriate terminal type. For example:
    TERM=hft
    export TERM

Edit /etc/filesystems. If you have been recreating /tmp, invoke the vi editor
by executing the following command:
    vi -c "set dir=/" /etc/filesystems

If you have not been recreating /tmp, execute:

    vi /etc/filesystems

Skip down to the stanza for either /var or /tmp. Within that stanza, go to the
line that says mount = false and change the word false to automatic. Save the file.


Change the ownership and permissions to the proper values, as follows:
    chmod g-s /var
    chmod 755 /var
    chown bin.bin /var
 
         or
 
    chmod g-s /tmp
    chmod 1777 /tmp
    chown bin.bin /tmp

Restore the files from your backup. If you used the backup method given
 earlier in this document, execute:
    cd /
    tar -xvf /dev/rmt0

Remove the bootable media if you have not already done so.

If your system has a mode select key, switch it to the Normal position.

Reboot the system into Normal mode with the following:
   sync;sync;sync;reboot