Mysqld startup error after mysql modifies Directory

Starting a mysql instance on a ubuntu testing machine should have been a simple task, but an error was reported during startup:

Mysqld_safe -- defaults-file =/etc/mysql/my3307.cnf
160218 15:45:13 mysqld_safe Can't log to error log and syslog at the same time. Remove all -- log-error configuration options for -- syslog to take effect.
160218 15:45:13 mysqld_safe Logging to '/var/log/mysql/error3307.log '.
160218 15:45:13 mysqld_safe Starting mysqld daemon with databases from/var/lib/mysql3307
160218 15:45:15 mysqld_safe mysqld from pid file/var/run/mysqld/mysqld3307.pid ended
View error logs/var/log/mysql/error3307.log

The ibdata file cannot be created due to permission issues:
 

160218 12:19:09 InnoDB: Completed initialization of buffer pool
160218 12:19:09 InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights
InnoDB: the directory.
InnoDB: File name./ibdata1
InnoDB: File operation call: 'create '.
InnoDB: Cannot continue operation.

In theory, you should have read and write permissions to view the directory:

Ls-ld/var/lib/mysql3307 drwx -- 4 mysql 4096 Feb 18/var/lib/mysql3307

Is there any other permission restriction?

Use dmesg to check whether there are some errors,

[4489099.208660] type = 1400 audit (1455768562.142: 57 ): apparmor = "DENIED" operation = "mknod" profile = "/usr/sbin/mysqld" name = "/var/lib/mysql3307/ibdata1" pid = 19775 comm = "mysqld" requested_mask = "c" denied_mask = "c" fsuid = 105 ouid = 105

View the configuration of/usr/sbin/mysqld:

Vi/etc/apparmor. d/usr. sbin. mysqld

Add the permission for the mysql3307 directory and restart apparmor:

/Var/lib/mysql3307/r,
/Var/lib/mysql3307/** rwk,
/Etc/init. d/apparmor restart

Restart mysqld again and report an error. However, the error message is different:

160218 12:44:03 [ERROR] Can't start server: Bind on unix socket: Permission denied
160218 12:44:03 [ERROR] Do you already have another mysqld server running on socket:/var/run/mysqld/mysqld3307.sock?
160218 12:44:03 [ERROR] Aborting

Dmesg can also see the error message:

[4491181.040673] type = 1400 audit (1455770643.975: 99 ): apparmor = "DENIED" operation = "mknod" profile = "/usr/sbin/mysqld" name = "/run/mysqld/mysqld3307.sock" pid = 24093 comm = "mysqld" requested_mask = "c" denied_mask = "c" fsuid = 105 ouid = 105
Add configuration to/etc/apparmor. d/usr. sbin. mysqld and restart apparmor.
/Var/run/mysqld/mysqld3307.pid rw,
/Var/run/mysqld/mysqld3307.sock w,
/Run/mysqld/mysqld3307.pid rw,
/Run/mysqld/mysqld3307.sock w,

Restart mysqld again or report an error, but this time it is a new error:

160218 12:57:27 [Note] Server socket created on IP: '0. 0.0.0 '.
160218 12:57:27 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'MySQL. Host' doesn' t exist
160218 12:57:27 mysqld_safe mysqld from pid file/var/run/mysqld/mysqld3307.pid ended
Run mysql_install_db-defaults-file =/etc/mysql/my3307.cnf
This time, mysqld can be started properly:
160218 14:44:59 [Note] Server socket created on IP: '0. 0.0.0 '.
160218 14:44:59 [Note] Event schedents: Loaded 0 events
160218 14:44:59 [Note]/usr/sbin/mysqld: ready for connections.
Version: '5. 5.46-0ubuntu0. 14.04.2 'socket: '/var/run/mysqld/mysqld3307.sock' port: 3307 (Ubuntu)