Today, MySQL server didn't start in the morning.
I checked log file of the server and found the following message:
121203 13:31:12 [ERROR] Can't start server: can't create PID file: No space left on device
121203 13:31:12 mysqld_safe Number of processes running now: 1
121203 13:31:12 mysqld_safe mysqld process hanging, pid 1708 - killed
121203 13:31:12 mysqld_safe mysqld restarted
121203 13:31:12 [Warning] '--default-character-set' is deprecated and will be removed in a future release. Please use '--character-set-server' instead.
I examined the usage of HDDs of the host.
$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_cloud-lv_root 953G 914G 0 100% /
tmpfs 3.3G 308K 3.3G 1% /dev/shm
/dev/sda1 485M 67M 393M 15% /boot
/dev/mapper/vg_cloud-lv_home 872G 249M 827G 1% /home
xenstore 3.8G 104K 3.8G 1%. /var/lib/xenstored
The reason was that I created a big sized virtual hard disk for my testing environment and it caused insufficient disk size. Now, I deleted this VHD and I will move to big sizes files to /dev/mapper/vg_cloud-lv_home to make enough space on root directory soon.