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I have a problem to move the default datadir of Maria DB to another partition, it appears to be very common but i tried everything I can without luck.

Mysql is installed as Mariadb 10.1.26 with the default debian package (apt-get install mysql-server) on a Debian 9.1 (stretch) server, mysqld -v returns mysqld 10.1.26-MariaDB-0+deb9u1

Default_mysql_datadir : /var/lib/mysql

New_mysql_datadir : /home/mysql

/var/lib/mysql is mounted to "/" (/dev/md3)

/home/mysql is mounted to "/home" (/dev/md4)

What I've tried

# systemctl stop mysql
# mv /var/lib/mysql /home

Change datadir in /etc/mysql/my.cnf

datadir = /home/mysql

Check if the rights/permissions are ok

# chown -R mysql.mysql /home/mysql

apparmor is NOT installed nor running on the system though the /etc/apparmor.d/usr.sbin.mysqld file is existing with the following rules :

/home/mysql/ r,
/home/mysql/** rwk,

I even tried to create and empty /var/lib/mysq folder refering to this bug

But when I start I always get the same error :

# systemctl start mysql
[Warning] Can't create test file /home/mysql/<user>.lower-test
#007/usr/sbin/mysqld: Can't change dir to '/home/mysql/' (Errcode: 13 "Permission denied") 2017-09-07  0:16:59 140119808397888 [ERROR] Aborting
mariadb.service: Main process exited, code=exited, status=1/FAILURE
Failed to start MariaDB database server.
mariadb.service: Unit entered failed state.
mariadb.service: Failed with result 'exit-code'.

Any suggestion ?

Thanks

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2 Answers 2

Reset to default
5

You must set ProtectHome=false in the systemd config file in order to move your datadir to the /home directory.

According to Debian policy rules, you should set this option value in a custom file like /etc/systemd/system/mariadb.service.d/YOUR_CUSTOM_FILE.conf containing:

[Service]

# Prevent accessing /home, /root and /run/user
ProtectHome=false

Then reload systemctl daemon:

systemctl daemon-reload

After that you should be able to change MariaDB datadir from /var/lib/mysql to /home/mysql.

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  • We just ran into this after a version upgrade on a production server. We had to add ProtectSystem=false in addition to ProtectHome=false. After adding ProtectHome=false, the error changed to: [ERROR] mysqld: File '/home/mysql/mysql-bin.index' not found (Errcode: 30 "Read-only file system") When it was clearly not actually a read only situation.
    – Jestep
    Feb 7, 2018 at 16:04
  • systemd documentation for mariadb contains this an other tips. Needing ProtectSystem=false seems odd. Did you miss running daemon-reload maybe?
    – danblack
    Feb 20, 2019 at 0:09
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This whitelist in /etc/systemd/mariadb.service.d/whatever.conf:

[Service]
ReadWritePaths=/home/mysql

may be another solution, but I would not have found it without Mr. Payart's wisdom.

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  • FYI: It turns out the ProtectHome=false is also required.
    – Brian Carcich
    Feb 21, 2019 at 11:09

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