Maintaining free space in filesystems

One important responsibility of the system administrator is ensuring that there is adequate disk space for the users. To do this, you must monitor the free space in each filesystem and take corrective action whenever free space gets too low. The amount of free space depends on the size of the disk containing the filesystem and the number of files on the disk. To determine how much free space is available in a filesystem, see ``Displaying filesystem and directory usage statistics''.

A UNIX system operates best when at least 15% of the space in each filesystem is free. If a filesystem has less than 15% free space, system operation typically becomes sluggish.

When a filesystem has little or no space left to work, the system displays the following:

   out of space on device

If the free space falls below 15%, you can do any of the following:

• Remove files from the /tmp directory.

• Remind users to remove unused files.

  You can include a reminder in the /etc/motd (message of the day) file, send e-mail, or send a message to the terminals of all users currently logged in. See mail(1) and wall(1M) (``write to all'').

• Locate large files and ask owners to remove them.

  See Finding files of a certain size.

• Locate system files to remove.

  See ``Finding temporary files''.
  

• Clear system log files.

  See ``Checking and clearing system log files''.
  

• Back up and remove unused data.

  For example, delete data in the /var/adm, such as the sar data in the /var/adm/sa directory or, if accounting is enabled, the data in the /var/adm/acct directory.

  Back up these files before removing them.

• Compress infrequently used files.

  See compress(1).

• Archive files into one larger file to free up inodes. See tar(1).

• Add more disk space.

  See ``Adding disk space and restructuring filesystems''.

• Add another disk and increase the size of the filesystem using the See Volume Manager.