SuSE eMail Server II, SuSE eMail Server III
Some services of the SuSE eMail Server are temporarily or completely
not available, with messages in /var/log/messages
about
'too many open files in system'. Mostly imapd is
affected.
For every single connection to one of the services (IMAP, SMTP, LDAP) the respective dæmon opens several files and sockets. These open files then get referenced by file descriptors. The number of descriptors is limited by the kernel and normally allows up to 8192 open files and sockets in the system.
This value can be too small for a system with many users accessing the services simultaniously, however.
Increase the number of file descriptors available through the /proc file system, in the following example to 65536:
echo "65536" >/proc/sys/fs/file-max
The kernel used for SuSE eMail Server II has another important parameter which affects the maximum number of open files. The maximum number of cached inodes, which should also be increased:
echo "131072" >/proc/sys/fs/inode-max
(This parameter does not exist anymore for Linux kernel 2.4 used by SuSE eMail Server III)
Both values should be as high as needed but as low as possible, yet with a little room left for times of high activity. Values too high waste too much memory while with values too low you will experience the problems again after a while, though less often. Furthermore the value inode-max should be larger than file-max.
To keep the adjustments over reboots you can add above commands
to the start script /etc/init.d/boot.local
(SuSE Linux
eMail Server II: /sbin/init.d/boot.local
)
Please note that we cannot offer support or any kind of liability for the consequences of using this hint.