cPanel recommend that you use a separate partition for /tmp that is mounted with nosetuid. Nosetuid will force a process to run with the privileges of it’s executor. You may also wish to mount /tmp with noexec after installing cPanel.

How to increase /tmp partition in cpanel

1. Stop cpanel, apache, mysql services and other webserver service.

/etc/init.d/cpanel stop
/etc/init.d/mysql stop
/etc/init.d/httpd stop

2. Try to Umount /tmp and /var/tmp

umount -l /tmp
umount -l /var/tmp

3. Move /usr/tmpDSK file to another location (just in case you’ll need to mount it somewhere else to preserve data):

mv /usr/tmpDSK /usr/tmpDSK_back

4. Modify /scripts/securetmp to set tmpdsksize. For example 2G size

vi /scripts/securetmp

$tmpdsksize = 2048000

5. Run:

/scripts/securetmp

6. Once completed, restart all the service.

/etc/init.d/cpanel start
/etc/init.d/httpd start
/etc/init.d/mysql start

You can increse /tmp partition size directly without scripts.

Stop all the service.

# /etc/init.d/mysql stop

# cp -af /var/tmp /var/tmp.bak

# umount /var/tmp

# umount /tmp

# mv /usr/tmpDSK /usr/tmpDSK_bak

Increase /tmp partition size to 2G

# dd if=/dev/zero of=/usr/tmpDSK bs=1024 count=2097195

# mkfs /usr/tmpDSK

# tune2fs -j /usr/tmpDSK

# mount -t ext3 -o nosuid,noexec,loop /usr/tmpDSK /tmp

# mount -o bind,noexec,nosuid /tmp /var/tmp

# cp -a /var/tmp.bak/* /tmp/

# rm -rf /var/tmp.bak

# chmod 1777 /tmp

Start all the service.