Too many open files error on Ubuntu 8.04

Question

mysqldump: Couldn't execute 'show fields from `tablename`': Out of resources when opening file './databasename/tablename#P#p125.MYD' (Errcode: 24) (23)

on checking the error 24 on the shell it says

>>perror 24

OS error code  24:  Too many open files

how do I solve this?

Answer 1

At first, to identify the certain user or group limits you have to do the following:

root@ubuntu:~# sudo -u mysql bash
mysql@ubuntu:~$ ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 71680
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 71680
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
mysql@ubuntu:~$

The important line is:

open files (-n) 1024

As you can see, your operating system vendor ships this version with the basic Linux configuration - 1024 files per process.

This is obviously not enough for a busy MySQL installation.

Now, to fix this you have to modify the following file:

/etc/security/limits.conf

mysql             soft    nofile           24000
mysql             hard    nofile           32000

Some flavors of Linux also require additional configuration to get this to stick to daemon processes versus login sessions. In Ubuntu 10.04, for example, you need to also set the pam session limits by adding the following line to /etc/pam.d/common-session:

session required pam_limits.so