Mysql. Bind on unix socket: Permission denied
1) First make sure you delete the existing socket file using the rm command.
rm /var/lib/mysql/mysql.sock
2) Kill all existing MySQL processes via the following command.
service mysql stop
3) Very important: Make sure the permission for the MySQL database directory under /var/lib/ folder should be mysql:root
chown -R mysql:root /var/lib/mysql
4) With the above information you should be able to start MySQL successfully and the socket file should be created successfully under the database directory.
service mysql start
Thanks to @Abhishek's answer combined with mysqld output(Can't use /var/run/mysqld/mysqld.sock) I managed to solve this with one command:
chown -R mysql:root /var/run/mysqld
Then it starts properly:
root@***:~# service mysql start
df: Warning: cannot read table of mounted file systems: No such file or directory
[ ok ] Starting MySQL database server: mysqld ..
[info] Checking for tables which need an upgrade, are corrupt or were
not closed cleanly..
Your problem can be caused by any condition that prevents the MySQL daemon from writing a socket file to the path /var/lib/mysql. The other answers, such as a read-only filesystem or incorrect directory ownership, address various reasons that MySQL may not be able to write to the socket.
Another possible reason is that /var/lib/mysql may have the incorrect SELinux context. You can diagnose this condition by checking for recent SELinux AVC denials after attempting to start the MySQL daemon:
ausearch -m avc --start recent
If SELinux is denying access to create the socket file, you will see an error message like this:
time->Thu Feb 2 03:46:27 2017
type=SYSCALL msg=audit(1566106187.784:152): arch=c000004e syscall=49 success=no exit=-13 a0=4f a1=7ff3fd652e80 a2=6e a3=7fcd2d6523d40 items=0 ppid=1 pid=1820 auid=4294967295 uid=996 gid=994 euid=996 suid=996 fsuid=996 egid=994 sgid=994 fsgid=994 tty=(none) ses=4294967295 comm="mysqld" exe="/usr/sbin/mysqld" subj=system_u:system_r:mysqld_t:s0 key=(null)
type=AVC msg=audit(1566106187.784:152): avc: denied { create } for pid=1820 comm="mysqld" name="mysql.sock" scontext=system_u:system_r:mysqld_t:s0 tcontext=system_u:object_r:var_log_t:s0 tclass=sock_file
To resolve an SELinux denial, try to restore the default context of the directory (your distribution should set the correct context of mysqld_db_t when you installed MySQL or MariaDB):
restorecon -R -v -f /var/lib/mysql
If you have customized the contexts on your system, fixing the problem is beyond the scope of this post.