root@colo18:~# mysqldump -u root --all-databases > colo18.sql
mysqldump: Couldn't execute 'show fields from `crongal`': Can't create/write to file '/tmp/#sql_b8c_0.MYI' (Errcode: 13) (1)

Lets set the proper permissions to /temp

sudo chmod 1777 /tmp

It will solve the issue.

Resources:

• http://askubuntu.com/questions/442536/mysql-couldnt-write-to-tmp-then-failed-to-restart/557531
• http://unix.stackexchange.com/questions/71622/what-are-common-rights-for-tmp-i-unintentionnally-set-it-all-public-recursive