failed to restart mysql.service: unit not found

1、查看此路径下有没有对应的mysql.service文件，有且只能有一个对应的文件名称
ps: 我这里面有两个是因为之前换过mysql的版本，可能没有删除干净导致重启MySQL服务不好使。如果你有两个以上的话，保留最新的

2、如果没有mysql.service。在第一步的路径下面添加一个，有且只有一个。

# Copyright (c) 2016, 2023, Oracle and/or its affiliates.## This program is free software; you can redistribute it and/or modify# it under the terms of the GNU General Public License, version 2.0,# as published by the Free Software Foundation.## This program is also distributed with certain software (including# but not limited to OpenSSL) that is licensed under separate terms,# as designated in a particular file or component or in included license# documentation.  The authors of MySQL hereby grant you an additional# permission to link the program and your derivative works with the# separately licensed software that they have included with MySQL.## This program is distributed in the hope that it will be useful,# but WITHOUT ANY WARRANTY; without even the implied warranty of# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the# GNU General Public License, version 2.0, for more details.## You should have received a copy of the GNU General Public License# along with this program; if not, write to the Free Software# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA## systemd service file for MySQL forking server#[Unit]Description=MySQL Server
Documentation=man:mysqld(8)Documentation=http://dev.mysql.com/doc/refman/en/using-systemd.html
After=network-online.target
Wants=network-online.target
After=syslog.target

[Install]WantedBy=multi-user.target

[Service]User=mysql
Group=mysql

Type=notify

# Disable service start and stop timeout logic of systemd for mysqld service.TimeoutSec=0# Execute pre and post scripts as rootPermissionsStartOnly=true

# Needed to create system tablesExecStartPre=/usr/bin/mysqld_pre_systemd %I

# Start main serviceExecStart=/usr/sbin/mysqld --defaults-group-suffix=@%I $MYSQLD_OPTS# Use this to switch malloc implementationEnvironmentFile=-/etc/sysconfig/mysql

# Sets open_files_limit
LimitNOFILE =10000Restart=on-failure

RestartPreventExitStatus=1# Set enviroment variable MYSQLD_PARENT_PID. This is required for restart.Environment=MYSQLD_PARENT_PID=1PrivateTmp=false

3、再次尝试重启MySQL服务命令

systemctl restart mysqld.service