剛好同事遇到 mysql 無法正常開啟，但重裝(sudo apt-get install mysql-server-5.6)時卻一直顯示
start: Job failed to start invoke-rc.d: initscript mysql, action “start” failed.
dpkg: error processing mysql-server-5.5 (—configure):
subprocess installed post-installation script returned error exit status 1
或是
Unable to set password for the mysql “root” user…
嘗試執行 mysql 也會寫著服務的 socket 未開啟
ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/var/run/mysqld/mysqld.sock’ (2)
去看了一下 mysql 的 error.log(var/log/mysql/error.log)
裡面則寫了
InnoDB: Error: unable to create temporary file; errno: 28
Plugin ‘InnoDB’ init function returned error
Plugin ‘InnoDB’ registration as a STORAGE ENGINE failed.
看起來可能是 /tmp 目錄的權限有問題
以下指令將 /tmp 資料夾的權限做了正確的調整，完整移除 mysql 的所有資料後，重新安裝就正常了!
(以下指令會將原本的 mysql 資料全部刪除，操作前請先做好備份)
sudo chmod /tmp 777
sudo service mysql stop
sudo killall -KILL mysql mysqld_safe mysqld
sudo apt-get purge mysql-server* mysql-client*
sudo apt-get autoremove --purge
sudo apt-get autoclean
sudo deluser --remove-home mysql
sudo delgroup mysql
sudo rm -rf /etc/apparmor.d/abstractions/mysql /etc/apparmor.d/cache/usr.sbin.mysqld /etc/mysql /var/lib/mysql /var/lib/mysql-files/ /var/log/mysql* /var/log/upstart/mysql.log* /var/run/mysqld
sudo updatedb
sudo apt-get install mysql-server-5.6