if you dont have apparmor or selinux issues, but still get errorcode 13's:
mysql must be able to access the full path. I.e. all folders must be mysql accessible, not just the one you intend in pointing to.
example, you try using this in your mysql configuration: tmp = /some/folder/on/disk
# will work, as user root:
mkdir -p /some/folder/on/disk
chown -R mysql:mysql /some
# will not work, also as user root:
mkdir -p /some/folder/on/disk
chown -R mysql:mysql /some/folder/on/disk
This maybe helpful for MySql with AppArmor
stop mysql :
sudo /etc/init.d/mysql stop
Create directory called /somewhere/tmp
Edit Config:
sudo vim /etc/mysql/my.cnf # or perhaps sudo vim /etc/mysql/mysql.conf.d/mysqld.cnf
change
tmpdir = /somewhere/tmp/
Then
sudo vim /etc/apparmor.d/usr.sbin.mysqld
Add
# Allow data dir access
/somewhere/ r,
/somewhere/** rwk,
sudo chown -R root:root /somewhere
sudo chmod -R 1777 /somewhere
Restart
sudo /etc/init.d/apparmor reload
sudo /etc/init.d/mysql restart
You can also set the TMPDIR environment variable.
In some situations (Docker in my case) it's more convenient to set an environment variable than to update a config file.
This is answered in the documentation:
Where MySQL Stores Temporary Files
On Unix, MySQL uses the value of the TMPDIR environment variable as the path name of the directory in which to store temporary files. If TMPDIR is not set, MySQL uses the system default, which is usually /tmp, /var/tmp, or /usr/tmp.
On Windows, Netware and OS2, MySQL checks in order the values of the TMPDIR, TEMP, and TMP environment variables. For the first one found to be set, MySQL uses it and does not check those remaining. If none of TMPDIR, TEMP, or TMP are set, MySQL uses the Windows system default, which is usually C:\windows\temp.
Here is an example to move the mysqld tmpdir from /tmp to /run/mysqld which already exists on Ubuntu 13.04 and is a tmpfs (memory/ram):
sudo vim /etc/mysql/conf.d/local.cnf
Add:
[mysqld]
tmpdir = /run/mysqld
Then:
sudo service mysql restart
Verify:
SHOW VARIABLES LIKE 'tmpdir';
==================================================================
If you get an error on MySQL restart, you may have AppArmor enabled:
sudo vim /etc/apparmor.d/local/usr.sbin.mysqld
Add:
# Site-specific additions and overrides for usr.sbin.mysqld.
# For more details, please see /etc/apparmor.d/local/README.
/run/mysqld/ r,
/run/mysqld/** rwk,
Then:
sudo service apparmor reload
sources: http://2bits.com/articles/reduce-your-servers-resource-usage-moving-mysql-temporary-directory-ram-disk.html, https://blogs.oracle.com/jsmyth/entry/apparmor_and_mysql
Source: Stackoverflow.com