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?
There is no guarantee that "24" is an OS-level error number, so don't assume that this means that too many file handles are open. It could be some type of internal error code used within mysql itself. I'd suggest asking on the mysql mailing lists about this.
Wait, I lied. In this case, 24 probably does mean what you think it means. At least one other person seems to have experienced this -- see this bug report on the mysql bug tracker, though this is a rather old report. Are you using mysql 5.0 by chance?
It could also be possible that by some code that accesses the tables dint close those properly and over a point of time, the number of open files could be reached.
Please refer to http://dev.mysql.com/doc/refman/5.0/en/table-cache.html for a possible reason as well.
Restarting mysql should cause this problem to go away (although it might happen again unless the underlying problem is fixed).
You can increase your OS limits by editing /etc/security/limits.conf.
You can also install "lsof" (LiSt Open Files) command to see Files <-> Processes relation.
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 you OS vendor ships this version with the basic Linux configuration which is 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