Today, I found that /tmp was showing 100% full but, After deleting all files from /tmp it was still showing full. After google it, I found that there are some file which deleted from /tmp folder but still used by process used all space. Generally these files used by apache or mysql.
Use following command to check files
# lsof | grep /tmp
mysqld 3236 mysql 6u REG 202,5 0 2373 /tmp/ibZzBzJ8 (deleted) mysqld 3236 mysql 7u REG 202,5 0 2378 /tmp/ibfoQY3a (deleted) mysqld 3236 mysql 11u REG 202,5 0 2393 /tmp/ibz2IDcI (deleted) mysqld 3236 mysql 220u REG 202,5 696842249 664 /tmp/ST1pexnQ (deleted) mysqld 3236 mysql 224u REG 202,5 1245184 683 /tmp/STfyPJQi (deleted) mysqld 3236 mysql 288u REG 202,5 226885632 748 /tmp/STF547ZN (deleted)
Check the output of above command and restart services according to it. In my case restarting mysql fixed issue.
# service mysqld restart
# service httpd restart
After restarting services all deleted tmp files will be cleared.