我能够在 WSL1 上重现您的问题（或看起来非常相似的问题）。您能否确认您使用的是 WSL1？
我创建了 Ubuntu 20.04 的两个克隆实例（wsl --import 的干净备份）——一个在 WSL1 上，另一个在 WSL2 上。不幸的是，我没有一个方便的 18.04 可以使用，但我希望问题是一样的。
在 WSL2 上，一切正常。在安装步骤之后（几乎是您在评论中添加的步骤，但对于 20.04），我能够：
sudo service mariadb start
然后sudo mysql -u root成功。
然而，在 WSL1 上，MariaDB 安装似乎以一种奇怪的方式失败。它不会创建/etc/mysql/mariadb.cnf，这会导致您看到空的/etc/mysql/my.cnf，因为它是mariadb.cnf 的符号链接。
所以我手动创建了 mariadb.cnf：
sudo vi /etc/mysql/mariadb.cnf
内容：
# The MariaDB configuration file
#
# The MariaDB/MySQL tools read configuration files in the following order:
# 0. "/etc/mysql/my.cnf" symlinks to this file, reason why all the rest is read.
# 1. "/etc/mysql/mariadb.cnf" (this file) to set global defaults,
# 2. "/etc/mysql/conf.d/*.cnf" to set global options.
# 3. "/etc/mysql/mariadb.conf.d/*.cnf" to set MariaDB-only options.
# 4. "~/.my.cnf" to set user-specific options.
#
# If the same option is defined multiple times, the last one will apply.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# If you are new to MariaDB, check out https://mariadb.com/kb/en/basic-mariadb-articles/
#
# This group is read both by the client and the server
# use it for options that affect everything
#
[client-server]
# Port or socket location where to connect
# port = 3306
socket = /run/mysqld/mysqld.sock
# Import all .cnf files from configuration directory
!includedir /etc/mysql/conf.d/
!includedir /etc/mysql/mariadb.conf.d/
这只是 WSL2 上安装正确创建的默认 mariadb.cnf。
尝试启动服务时出现了一个关于缺少/etc/mysql/debian-start 的错误，所以我重复了相同的步骤将其复制过来：
sudo vi /etc/mysql/debian-start
附内容：
#!/bin/bash
#
# This script is executed by "/etc/init.d/mariadb" on every (re)start.
#
# Changes to this file will be preserved when updating the Debian package.
#
# NOTE: This file is read only by the traditional SysV init script, not systemd.
#
source /usr/share/mysql/debian-start.inc.sh
# Read default/mysql first and then default/mariadb just like the init.d file does
if [ -f /etc/default/mysql ]; then
. /etc/default/mysql
fi
if [ -f /etc/default/mariadb ]; then
. /etc/default/mariadb
fi
MYSQL="/usr/bin/mysql --defaults-file=/etc/mysql/debian.cnf"
MYADMIN="/usr/bin/mysqladmin --defaults-file=/etc/mysql/debian.cnf"
# Don't run full mysql_upgrade on every server restart, use --version-check to do it only once
MYUPGRADE="/usr/bin/mysql_upgrade --defaults-extra-file=/etc/mysql/debian.cnf --version-check"
MYCHECK="/usr/bin/mysqlcheck --defaults-file=/etc/mysql/debian.cnf"
MYCHECK_SUBJECT="WARNING: mysqlcheck has found corrupt tables"
MYCHECK_PARAMS="--all-databases --fast --silent"
MYCHECK_RCPT="${MYCHECK_RCPT:-root}"
## Checking for corrupt, not cleanly closed (only for MyISAM and Aria engines) and upgrade needing tables.
# The following commands should be run when the server is up but in background
# where they do not block the server start and in one shell instance so that
# they run sequentially. They are supposed not to echo anything to stdout.
# If you want to disable the check for crashed tables comment
# "check_for_crashed_tables" out.
# (There may be no output to stdout inside the background process!)
# Need to ignore SIGHUP, as otherwise a SIGHUP can sometimes abort the upgrade
# process in the middle.
trap "" SIGHUP
(
upgrade_system_tables_if_necessary;
check_root_accounts;
check_for_crashed_tables;
) >&2 &
exit 0
然后chmod 755 /etc/mysql/debian-start
然后，瞧：
sudo service mariadb restart
sudo mysql -u root
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 32
Server version: 10.5.8-MariaDB-1:10.5.8+maria~focal 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)]>
鉴于您迄今为止尝试过的步骤，我建议您放弃几乎所有步骤以尝试“干净”重新开始：
sudo apt remove mariadb-server
sudo apt autoremove
sudo rm -rf /etc/mysql
sudo rm -rf /var/lib/mysql
sudo rm -rf /usr/lib/mysql
然后重新安装 mariadb-server 并按照上述步骤创建正确的文件。