显然清除和/或重新安装mysql可能mariadb会导致冲突，因此尝试：
root@mordor:~#
root@mordor:~# sudo apt purge mariadb-server mariadb-client mysql-client mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package 'mysql-client' is not installed, so not removed
Package 'mysql-server' is not installed, so not removed
The following packages will be REMOVED:
mariadb-client* mariadb-server*
0 upgraded, 0 newly installed, 2 to remove and 1 not upgraded.
After this operation, 20.5 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 181581 files and directories currently installed.)
Removing mariadb-client (1:10.4.17+maria~focal) ...
Removing mariadb-server (1:10.4.17+maria~focal) ...
root@mordor:~#
root@mordor:~#
root@mordor:~# rm -rf /var/lib/mysql
root@mordor:~#
root@mordor:~# sudo apt install mariadb-client mariadb-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
mariadb-client mariadb-server
0 upgraded, 2 newly installed, 0 to remove and 1 not upgraded.
Need to get 0 B/6252 B of archives.
After this operation, 20.5 kB of additional disk space will be used.
Selecting previously unselected package mariadb-client.
(Reading database ... 181576 files and directories currently installed.)
Preparing to unpack .../mariadb-client_1%3a10.4.17+maria~focal_all.deb ...
Unpacking mariadb-client (1:10.4.17+maria~focal) ...
Selecting previously unselected package mariadb-server.
Preparing to unpack .../mariadb-server_1%3a10.4.17+maria~focal_all.deb ...
Unpacking mariadb-server (1:10.4.17+maria~focal) ...
Setting up mariadb-client (1:10.4.17+maria~focal) ...
Setting up mariadb-server (1:10.4.17+maria~focal) ...
root@mordor:~#
root@mordor:~# mariadb
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
root@mordor:~#
root@mordor:~# systemctl status mariadb.service
● mariadb.service - MariaDB 10.4.17 database server
Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/mariadb.service.d
└─migrated-from-my.cnf-settings.conf
Active: failed (Result: exit-code) since Sat 2020-11-14 10:43:31 PST; 1h 23min ago
Docs: man:mysqld(8)
https://mariadb.com/kb/en/library/systemd/
Main PID: 90075 (code=exited, status=1/FAILURE)
Status: "MariaDB server is down"
Nov 14 10:43:29 mordor systemd[1]: Starting MariaDB 10.4.17 database server...
Nov 14 10:43:29 mordor mysqld[90075]: 2020-11-14 10:43:29 0 [Note] /usr/sbin/mysqld (mysqld 10.4.17-MariaDB-1:10.4.17+maria~focal-l>
Nov 14 10:43:29 mordor mysqld[90075]: 2020-11-14 10:43:29 0 [Warning] Could not increase number of max_open_files to more than 1638>
Nov 14 10:43:29 mordor mysqld[90075]: 2020-11-14 10:43:29 0 [Warning] Changed limits: max_open_files: 16384 max_connections: 500 (>
Nov 14 10:43:31 mordor systemd[1]: mariadb.service: Main process exited, code=exited, status=1/FAILURE
Nov 14 10:43:31 mordor systemd[1]: mariadb.service: Failed with result 'exit-code'.
Nov 14 10:43:31 mordor systemd[1]: Failed to start MariaDB 10.4.17 database server.
root@mordor:~#
我该如何开始mariadb？我可以再次清除它，但这只是一个循环。
答案1
首先检查 mariadb 是否正在运行。如果没有运行，则无法连接。
你忘了做
sudo mysql_secure_installation
设置用户和密码。
关于此命令请还...
- 删除匿名用户
- 删除测试数据库
- 禁止远程 root 登录
一般来说你也可以这样做：
sudo -i
{admin password}
mariadb
然后设置用户和密码。尽量避免使用常用名称作为用户（即，没有root，admin您的用户名等），并使用个人用户名。这会使别人需要猜测更多的事情。
答案2
至少可以进入数据库：
root@mordor:~#
root@mordor:~# sudo apt purge mariadb-server-core-10.4 mariadb-server-10.4 mariadb-client-core-10.4 mariadb-client-10.4
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package 'mariadb-client-10.4' is not installed, so not removed
Package 'mariadb-client-core-10.4' is not installed, so not removed
Package 'mariadb-server-10.4' is not installed, so not removed
Package 'mariadb-server-core-10.4' is not installed, so not removed
The following packages were automatically installed and are no longer required:
galera-4 libdbd-mysql-perl libdbi-perl libterm-readkey-perl socat
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
root@mordor:~#
root@mordor:~# sudo apt purge mysql-server-core-8.0 mysql-server-8.0 mysql-client-core-8.0 mysql-client-8.0
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package 'mysql-client-8.0' is not installed, so not removed
Package 'mysql-client-core-8.0' is not installed, so not removed
Package 'mysql-server-8.0' is not installed, so not removed
Package 'mysql-server-core-8.0' is not installed, so not removed
The following packages were automatically installed and are no longer required:
galera-4 libdbd-mysql-perl libdbi-perl libterm-readkey-perl socat
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
root@mordor:~#
root@mordor:~# rm -rf /var/lib/mysql
root@mordor:~#
root@mordor:~# sudo apt install mariadb-client mariadb-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
mariadb-client-10.4 mariadb-client-core-10.4 mariadb-server-10.4 mariadb-server-core-10.4
Suggested packages:
mailx mariadb-test tinyca
The following NEW packages will be installed:
mariadb-client mariadb-client-10.4 mariadb-client-core-10.4 mariadb-server mariadb-server-10.4 mariadb-server-core-10.4
0 upgraded, 6 newly installed, 0 to remove and 1 not upgraded.
Need to get 0 B/12.9 MB of archives.
After this operation, 142 MB of additional disk space will be used.
Do you want to continue? [Y/n]
Preconfiguring packages ...
Selecting previously unselected package mariadb-client-core-10.4.
(Reading database ... 181260 files and directories currently installed.)
Preparing to unpack .../0-mariadb-client-core-10.4_1%3a10.4.17+maria~focal_amd64.deb ...
Unpacking mariadb-client-core-10.4 (1:10.4.17+maria~focal) ...
Selecting previously unselected package mariadb-client-10.4.
Preparing to unpack .../1-mariadb-client-10.4_1%3a10.4.17+maria~focal_amd64.deb ...
Unpacking mariadb-client-10.4 (1:10.4.17+maria~focal) ...
Selecting previously unselected package mariadb-server-core-10.4.
Preparing to unpack .../2-mariadb-server-core-10.4_1%3a10.4.17+maria~focal_amd64.deb ...
Unpacking mariadb-server-core-10.4 (1:10.4.17+maria~focal) ...
Selecting previously unselected package mariadb-server-10.4.
Preparing to unpack .../3-mariadb-server-10.4_1%3a10.4.17+maria~focal_amd64.deb ...
Unpacking mariadb-server-10.4 (1:10.4.17+maria~focal) ...
Selecting previously unselected package mariadb-client.
Preparing to unpack .../4-mariadb-client_1%3a10.4.17+maria~focal_all.deb ...
Unpacking mariadb-client (1:10.4.17+maria~focal) ...
Selecting previously unselected package mariadb-server.
Preparing to unpack .../5-mariadb-server_1%3a10.4.17+maria~focal_all.deb ...
Unpacking mariadb-server (1:10.4.17+maria~focal) ...
Setting up mariadb-server-core-10.4 (1:10.4.17+maria~focal) ...
Setting up mariadb-client-core-10.4 (1:10.4.17+maria~focal) ...
Setting up mariadb-client-10.4 (1:10.4.17+maria~focal) ...
Setting up mariadb-client (1:10.4.17+maria~focal) ...
Setting up mariadb-server-10.4 (1:10.4.17+maria~focal) ...
Failed to stop mysql.service: Unit mysql.service not loaded.
Created symlink /etc/systemd/system/mysql.service → /lib/systemd/system/mariadb.service.
Created symlink /etc/systemd/system/mysqld.service → /lib/systemd/system/mariadb.service.
Created symlink /etc/systemd/system/multi-user.target.wants/mariadb.service → /lib/systemd/system/mariadb.service.
Setting up mariadb-server (1:10.4.17+maria~focal) ...
Processing triggers for man-db (2.9.1-1) ...
root@mordor:~#
root@mordor:~# sudo mysql_secure_installation
NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB
SERVERS IN PRODUCTION USE! PLEASE READ EACH STEP CAREFULLY!
In order to log into MariaDB to secure it, we'll need the current
password for the root user. If you've just installed MariaDB, and
haven't set the root password yet, you should just press enter here.
Enter current password for root (enter for none):
OK, successfully used password, moving on...
Setting the root password or using the unix_socket ensures that nobody
can log into the MariaDB root user without the proper authorisation.
You already have your root account protected, so you can safely answer 'n'.
Switch to unix_socket authentication [Y/n] n
... skipping.
You already have your root account protected, so you can safely answer 'n'.
Change the root password? [Y/n] y
New password:
Re-enter new password:
Password updated successfully!
Reloading privilege tables..
... Success!
By default, a MariaDB installation has an anonymous user, allowing anyone
to log into MariaDB without having to have a user account created for
them. This is intended only for testing, and to make the installation
go a bit smoother. You should remove them before moving into a
production environment.
Remove anonymous users? [Y/n]
... Success!
Normally, root should only be allowed to connect from 'localhost'. This
ensures that someone cannot guess at the root password from the network.
Disallow root login remotely? [Y/n]
... Success!
By default, MariaDB comes with a database named 'test' that anyone can
access. This is also intended only for testing, and should be removed
before moving into a production environment.
Remove test database and access to it? [Y/n]
- Dropping test database...
... Success!
- Removing privileges on test database...
... Success!
Reloading the privilege tables will ensure that all changes made so far
will take effect immediately.
Reload privilege tables now? [Y/n]
... Success!
Cleaning up...
All done! If you've completed all of the above steps, your MariaDB
installation should now be secure.
Thanks for using MariaDB!
root@mordor:~#
root@mordor:~# mariadb -u root
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 57
Server version: 10.4.17-MariaDB-1:10.4.17+maria~focal-log mariadb.org binary distribution
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> exit
Bye
root@mordor:~#
或者作为普通用户：
nicholas@mordor:~$
nicholas@mordor:~$ mariadb -u root -p
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 60
Server version: 10.4.17-MariaDB-1:10.4.17+maria~focal-log mariadb.org binary distribution
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]>
MariaDB [(none)]> exit
Bye
nicholas@mordor:~$