Service question

[Spinnifex]

Hello
I have some quesiton about linux service unit.

For example mysql.service.

Here is the ouput of

Code: Select all

systemctl status mysql.service


Code: Select all

● mysqld.service - MySQL database server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since Sat 2020-04-11 17:41:59 CEST; 1h 12min left
 Main PID: 4551 (mysqld)
   Status: "Taking your SQL requests now..."
   Memory: 66.7M
   CGroup: /system.slice/mysqld.service
           └─4551 /usr/sbin/mysqld

Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 2020-04-11 17:41:59 0 [Note] InnoDB: Waiting for purge to start
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 2020-04-11 17:41:59 0 [Note] InnoDB: 10.3.22 started; log sequence number 1625716; transaction id 21
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 2020-04-11 17:41:59 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql/ib_buffer_pool
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 200411 17:41:59 server_audit: MariaDB Audit Plugin version 1.4.8 STARTED.
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 200411 17:41:59 server_audit: Query cache is enabled with the TABLE events. Some table reads can be veiled.2020-04-11 17:41:59 0 [Note] InnoDB: Buffer pool(s) load completed at 200411 17:41:59
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 2020-04-11 17:41:59 0 [Note] Reading of all Master_info entries succeeded
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 2020-04-11 17:41:59 0 [Note] Added new Master_info '' to hash table
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: 2020-04-11 17:41:59 0 [Note] /usr/sbin/mysqld: ready for connections.
Apr 11 17:41:59 localhost.localdomain mysqld[4551]: Version: '10.3.22-MariaDB'  socket: '/var/lib/mysql/mysql.sock'  port: 0  Mageia MariaDB Server
Apr 11 17:41:59 localhost.localdomain systemd[1]: Started MySQL database server.


My questions

1. What means disabled/enabled
2. What means CGroup
3. localhost.localdomain systemd[1]: Started MySQL database server
So do I need to start this service by hand each time I want to use mysql?
4. I had a shutdown error because the mysql service did not stop. I waited over 5 min and this service did not stop. So I disable the service again. How can I avoid this?

Regards

Spinnifex

[doktor5000]

1. What means disabled/enabled

In what context? For the whole service or the vendor preset? enabled/disabled for the service defines whether it should start at boot-time.
See https://www.freedesktop.org/software/systemd/man/systemctl.html#enable%20UNIT%E2%80%A6 / https://www.freedesktop.org/software/systemd/man/systemctl.html#disable%20UNIT%E2%80%A6

2. What means CGroup

cgroups are control groups, this a kernel mechanism for controlling ressources.
See https://www.kernel.org/doc/Documentatio ... groups.txt / https://www.kernel.org/doc/Documentation/cgroup-v2.txt or maybe http://0pointer.de/blog/projects/resources.html

3. localhost.localdomain systemd[1]: Started MySQL database server
So do I need to start this service by hand each time I want to use mysql?

No, as it's already starting at boot time, as far as I can tell. But if it would not be enabled, then yes you would have to start it once per each boot where you want to use it - as with every other service.

4. I had a shutdown error because the mysql service did not stop. I waited over 5 min and this service did not stop. So I disable the service again. How can I avoid this?

Well better check why it will not shutdown. What did you do after the 5 minutes ?