Unable to start MYSQL service after data directory change - mysql

Question

This is going to be a long one. Please read.
I created an new Azure Ubuntu 18.04 with a 1 TB drive. Setup went fine. Then I installed MySql server using this link. Everything went fine. I was able to start up the mysql with no issues.
My next step was to change the data directory path. I followed this guide. The only difference I changed from the guide was the sudo rsync -av /var/lib/mysql /mnt/MYSQLDATA. When I ran that command, it didn't do anything. Nothing copied over. I replace it with cp * -r /mnt/MYSQLDATA to copy everything over.
I followed the guide to the end. I changed the cnf for mysql /etc/mysql/mysql.conf.d/mysqld.cnf to read:
datadir = /mnt/MYSQLDATA
Next, I changed the alias also sudo nano /etc/apparmor.d/tunables/alias:
`# alias /var/lib/mysql/ -> /mnt/MYSQLDATA/`,
I figured I had to change the [/etc/apparmor.d/usr.sbin.mysqld][3] config. This is the code I used:
# Allow data dir access
/mnt/MYSQLDATA/ r,
/mnt/MYSQLDATA** rwk,
Restarted the apparmor. Everything looked like it was set. I even went to make sure that mysql was the owner of the folder path, so I can chown -R mysql:mysql /mnt/MYSQLDATA. Now it was time to restart the service and it doesnt restart. I keep getting
Job for mysql.service failed because the control process exited with an error code. See "systemctl status mysql.service" and "journalctl -xe" for details.
2022-07-18T23:01:30.236755Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2022-07-18T23:01:30.236994Z 0 [Warning] Can't create test file /mnt/MYSQLDATA/LEGMYSQLR.lower-test
2022-07-18T23:01:30.237046Z 0 [Note] /usr/sbin/mysqld (mysqld 5.7.38-0ubuntu0.18.04.1) starting as process 7569 ...
2022-07-18T23:01:30.240273Z 0 [Warning] Can't create test file /mnt/MYSQLDATA/LEGMYSQLR.lower-test
2022-07-18T23:01:30.240311Z 0 [Warning] Can't create test file /mnt/MYSQLDATA/LEGMYSQLR.lower-test
2022-07-18T23:01:30.244072Z 0 [Note] InnoDB: PUNCH HOLE support available
2022-07-18T23:01:30.244101Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2022-07-18T23:01:30.244106Z 0 [Note] InnoDB: Uses event mutexes
2022-07-18T23:01:30.244110Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
2022-07-18T23:01:30.244131Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.11
2022-07-18T23:01:30.244135Z 0 [Note] InnoDB: Using Linux native AIO
2022-07-18T23:01:30.244437Z 0 [Note] InnoDB: Number of pools: 1
2022-07-18T23:01:30.244573Z 0 [Note] InnoDB: Using CPU crc32 instructions
2022-07-18T23:01:30.247391Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2022-07-18T23:01:30.255749Z 0 [Note] InnoDB: Completed initialization of buffer pool
2022-07-18T23:01:30.258357Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
2022-07-18T23:01:30.268405Z 0 [ERROR] InnoDB: The innodb_system data file 'ibdata1' must be writable
2022-07-18T23:01:30.268428Z 0 [ERROR] InnoDB: The innodb_system data file 'ibdata1' must be writable
2022-07-18T23:01:30.268444Z 0 [ERROR] InnoDB: Plugin initialization aborted with error Generic error
2022-07-18T23:01:30.869299Z 0 [ERROR] Plugin 'InnoDB' init function returned error.
2022-07-18T23:01:30.869354Z 0 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2022-07-18T23:01:30.869360Z 0 [ERROR] Failed to initialize builtin plugins.
2022-07-18T23:01:30.869364Z 0 [ERROR] Aborting
2022-07-18T23:01:30.869421Z 0 [Note] Binlog end
2022-07-18T23:01:30.869518Z 0 [Note] Shutting down plugin 'CSV'
2022-07-18T23:01:30.869895Z 0 [Note] /usr/sbin/mysqld: Shutdown complete
I have no idea what I did wrong and where it went wrong. In the journalctl -xe it just shows mysql.services: control process exited, code=exited status=1 or mysql.services: start request repeated too quickly. I am pulling my hair out trying to figure out what went wrong. Please help.

Answer 1

I was also running into similar problem.
The main problem was /mnt/mysqldisk/mysql the mysqldisk was created by my user so in the /var/log/syslog it was complaining it could not write to mysql directory.
I changed the permissions to mysql:mysql using shown on the directory. that should solve your problem
The easiest solution I found is using softlink
This is the final solution I did and you don't need to go through any complicated steps
-stop the mysql server
-sudo cp -a /var/lib/mysql /mnt/mysqldisk/mysql
-sudo mv /var/lib/mysql /var/lib/mysql.bak
` #create a soft link that points to the new mount mysql directory
sudo ln -s /mnt/mysqldisk/mysql/ /var/lib/mysql
Start the mysql service and check it comes up.
you do not need to do any change to /etc/mysql/mysql.conf.d/mysqld.cnf or any Alias etc.
This since to the mysql it looks as if mysql is still at the same place and the original config will still be able to access the new location from the soft link.
This is on ubuntu 18.04 LTS