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I am trying to move MySQL's data dir to an external drive on an odroid (raspberry-like mini computer).

I am using Ubuntu 14.04.

I changed the paths in all configuration files containing /var/lib/mysql and moved all mysql folders on my new drive.

The service does not start anymore and I dont know how to fix that.

Here are all changed paths:

root@odroid-server:/etc# grep -rnw '/etc' -e "/var/lib/mysql" root@odroid-server:/etc# grep -rnw '/etc' -e "/media/md0/mysql" /etc/apparmor.d/abstractions/mysql:12: /media/md0/mysql{,d}/mysql{,d}.sock rw, /etc/apparmor.d/tunables/alias:16:# alias /media/md0/mysql/ -> /home/mysql/, /etc/apparmor.d/usr.sbin.mysqld:49: /media/md0/mysql/ r, /etc/apparmor.d/usr.sbin.mysqld:50: /media/md0/mysql/** rwk, /etc/apparmor.d/usr.sbin.mysqld:53: /media/md0/mysql-files/ r, /etc/apparmor.d/usr.sbin.mysqld:54: /media/md0/mysql-files/** rwk, /etc/apparmor.d/usr.sbin.mysqld:57: /media/md0/mysql-keyring/ r, /etc/apparmor.d/usr.sbin.mysqld:58: /media/md0/mysql-keyring/** rwk, /etc/imscp/imscp.conf:37:DATABASE_DIR = /media/md0/mysql /etc/mysql/mysql.conf.d/mysqld.cnf:36:datadir = /media/md0/mysql /etc/mysql/mysql.conf.d/mysqld.cnf:92:# InnoDB is enabled by default with a 10MB datafile in /media/md0/mysql/. /etc/mysql/mysql.conf.d/mysqld.cnf:98:# chroot = /media/md0/mysql/

Then starting the service:

root@odroid-server:/etc# service mysql start Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.

I tried that command for more details and I can see that it still uses the old mysql datadir.

root@odroid-server:/etc# journalctl -xe Nov 18 13:06:45 odroid-server systemd[1]: Starting MySQL Community Server... -- Subject: Unit mysql.service has begun start-up -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel -- -- Unit mysql.service has begun starting up. Nov 18 13:06:45 odroid-server mysql-systemd-start[24276]: MySQL data dir not found at /var/lib/mysql. Please create one. Nov 18 13:06:45 odroid-server systemd[1]: mysql.service: Control process exited, code=exited status=1 Nov 18 13:06:45 odroid-server systemd[1]: Failed to start MySQL Community Server. -- Subject: Unit mysql.service has failed -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel -- -- Unit mysql.service has failed. -- -- The result is failed. Nov 18 13:06:45 odroid-server systemd[1]: mysql.service: Unit entered failed state. Nov 18 13:06:45 odroid-server systemd[1]: mysql.service: Failed with result 'exit-code'. Nov 18 13:06:45 odroid-server systemd[1]: mysql.service: Service hold-off time over, scheduling restart. Nov 18 13:06:45 odroid-server systemd[1]: Stopped MySQL Community Server. -- Subject: Unit mysql.service has finished shutting down -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel -- -- Unit mysql.service has finished shutting down. Nov 18 13:06:45 odroid-server systemd[1]: mysql.service: Start request repeated too quickly. Nov 18 13:06:45 odroid-server systemd[1]: Failed to start MySQL Community Server. -- Subject: Unit mysql.service has failed -- Defined-By: systemd -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel -- -- Unit mysql.service has failed. -- -- The result is failed.

Maybe there is some command to reload the configuration files back into ram?

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  • put the following line in your /etc/my.cfg file. log-error=/var/log/mysqld.log Is the data dir owned by the mysql user? Commented Nov 18, 2016 at 12:55
  • 2
    symlink /var/lib/mysql to new directory Commented Nov 18, 2016 at 13:37
  • Just do what @IporSircer said. Making symlinks instead of changing config files will avoid that kind of problems + no need to change any configuration + no need to write much extra documentation :D Commented Nov 18, 2016 at 16:49
  • symlinking worked indeed! i would accept that as an answer! Commented Nov 19, 2016 at 20:26

3 Answers 3

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From the comments:

Simply symlink /var/lib/mysql to the new directory.

Making symlinks is a quick, easy way of moving important files and directories. No need to change any configuration, and there is minimal documentation to keep track of.

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I just found a solution for this (years after it happened to me time).

The problem simply was that ubuntu server shipps with the malware apparmor. I only noticed that after inspecting dmesg. To get rid of it I simply ran

sudo apt remove --purge apparmor -y

and this made mysql start with my new mysql datadir (and fixed other problems too).

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SELINUX might also be the cause of your grief. Review my blogpost for more details on how to fix: https://sysengineers.wordpress.com/2021/03/22/mysqld-fails-to-start-after-moving-its-data-directory/

ps. Do note that apparmor and SELinux improves the overall security of your linux environment. Removing them might fix the issue at hand but will leave your install more vulnerable.

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  • In my experience, AppArmor profiles often include the standard data-location. Meaning, if you move the data location via my.conf, AppArmor will prevent MySQL from writing to the new location. Commented Mar 23, 2021 at 0:09

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