我对 Linux 还不熟悉，正在 Windows 上的 Virtualbox 中测试各种 LAMP 设置。目前，我有一台 Centos 7 VM，正在尝试在其上安装 MariaDB。我遵循以下说明：http://www.tecmint.com/install-lamp-in-centos-7
我跑了
# yum install mariadb-server mariadb
根据终端输出，安装成功，但是当我运行时：
# systemctl start mariadb
我明白了
Failed to start mariadb.service: Unit not found.
我花了几个小时在谷歌上搜索这个问题，但似乎没有什么能解决我的问题，包括这个（mariadb-server 安装后没有 mysqld 或 mysql.server) 以及许多其他帖子。
任何帮助是极大的赞赏。
更新 01
我卸载了 mariadb：
[root@centos7 admin]# yum remove mysql
Loaded plugins: fastestmirror
Resolving Dependencies
--> Running transaction check
---> Package MariaDB-client.x86_64 0:10.0.30-1.el7.centos will be erased
--> Processing Dependency: MariaDB-client for package: MariaDB-server-10.0.30-1.el7.centos.x86_64
--> Running transaction check
---> Package MariaDB-server.x86_64 0:10.0.30-1.el7.centos will be erased
--> Finished Dependency Resolution
Dependencies Resolved
===================================================================================
Package Arch Version Repository Size
===================================================================================
Removing:
MariaDB-client x86_64 10.0.30-1.el7.centos @mariadb 49 M
Removing for dependencies:
MariaDB-server x86_64 10.0.30-1.el7.centos @mariadb 237 M
Transaction Summary
===================================================================================
Remove 1 Package (+1 Dependent package)
Installed size: 286 M
Is this ok [y/N]: y
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Erasing : MariaDB-server-10.0.30-1.el7.centos.x86_64 1/2
Erasing : MariaDB-client-10.0.30-1.el7.centos.x86_64 2/2
Verifying : MariaDB-client-10.0.30-1.el7.centos.x86_64 1/2
Verifying : MariaDB-server-10.0.30-1.el7.centos.x86_64 2/2
Removed:
MariaDB-client.x86_64 0:10.0.30-1.el7.centos
Dependency Removed:
MariaDB-server.x86_64 0:10.0.30-1.el7.centos
Complete!
跑了yum clean all，yum update
重新安装 mariadb：
# yum install mariadb-server mariadb
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* Webmin: download.webmin.com
* base: anorien.csc.warwick.ac.uk
* extras: centos.mirrors.nublue.co.uk
* updates: centos.serverspace.co.uk
Package mariadb-server is obsoleted by MariaDB-server, trying to install MariaDB-server-10.0.30-1.el7.centos.x86_64 instead
Package mariadb is obsoleted by MariaDB-client, trying to install MariaDB-client-10.0.30-1.el7.centos.x86_64 instead
Resolving Dependencies
--> Running transaction check
---> Package MariaDB-client.x86_64 0:10.0.30-1.el7.centos will be installed
---> Package MariaDB-server.x86_64 0:10.0.30-1.el7.centos will be installed
--> Finished Dependency Resolution
Dependencies Resolved
===================================================================================
Package Arch Version Repository Size
===================================================================================
Installing:
MariaDB-client x86_64 10.0.30-1.el7.centos mariadb 10 M
MariaDB-server x86_64 10.0.30-1.el7.centos mariadb 55 M
Transaction Summary
===================================================================================
Install 2 Packages
Total download size: 65 M
Installed size: 65 M
Is this ok [y/d/N]: y
Downloading packages:
(1/2): MariaDB-10.0.30-centos7-x86_64-client.rpm | 10 MB 00:00:22
(2/2): MariaDB-10.0.30-centos7-x86_64-server.rpm | 55 MB 00:01:15
-----------------------------------------------------------------------------------
Total 876 kB/s | 65 MB 01:15
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : MariaDB-client-10.0.30-1.el7.centos.x86_64 1/2
Installing : MariaDB-server-10.0.30-1.el7.centos.x86_64 2/2
libsemanage.map_file: Unable to open /usr/share/mysql/SELinux/mariadb.pp
(No such file or directory).
libsemanage.semanage_direct_install_file: Unable to read file /usr/share/mysql/SELinux/mariadb.pp
(No such file or directory).
/usr/sbin/semodule: Failed on /usr/share/mysql/SELinux/mariadb.pp!
Verifying : MariaDB-client-10.0.30-1.el7.centos.x86_64 1/2
Verifying : MariaDB-server-10.0.30-1.el7.centos.x86_64 2/2
Installed:
MariaDB-client.x86_64 0:10.0.30-1.el7.centos
MariaDB-server.x86_64 0:10.0.30-1.el7.centos
Complete!
还是不行，怎么回事？
# systemctl start mariadb.service
Failed to start mariadb.service: Unit not found.
更新 02
软件包版本和大小写可能存在问题，我使用 mariaDB repos 而不是 centos 进行安装，因此它选择了版本 10.0.30：
]# yum info mariadb-server
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* Webmin: download.webmin.com
* base: anorien.csc.warwick.ac.uk
* extras: centos.mirrors.nublue.co.uk
* updates: centos.serverspace.co.uk
Installed Packages
Name : MariaDB-server
Arch : x86_64
Version : 10.0.30
Release : 1.el7.centos
Size : 237 M
Repo : installed
From repo : mariadb
Summary : MariaDB: a very fast and robust SQL database server
URL : http://mariadb.org
License : GPLv2
Description : MariaDB: a very fast and robust SQL database server
:
: It is GPL v2 licensed, which means you can use the it free of charge
: under the conditions of the GNU General Public License Version 2
: (http://www.gnu.org/licenses/).
:
: MariaDB documentation can be found at https://mariadb.com/kb
: MariaDB bug reports should be submitted through
: https://jira.mariadb.org
Available Packages
Name : mariadb-server
Arch : x86_64
Epoch : 1
Version : 5.5.52
Release : 1.el7
Size : 11 M
Repo : base/7/x86_64
Summary : The MariaDB server and related files
URL : http://mariadb.org
License : GPLv2 with exceptions and LGPLv2 and BSD
Description : MariaDB is a multi-user, multi-threaded SQL database server. It is a
: client/server implementation consisting of a server daemon (mysqld)
: and many different client programs and libraries. This package
: contains the MariaDB server and some accompanying files and
: directories. MariaDB is a community developed branch of MySQL.
答案1
进一步的研究表明，在 MariaDB repo (v 10.0.30) 中服务被称为，mysql而在 centos repo (v5.5) 中它被称为mariadb，所以这是一个混淆/问题。
参考问题：Centos7 上的 MariaDB，服务仍称为 MySql
跑动# service mysql start返回ERROR
使用 grep 命令检查错误：
journalctl -xe|grep 'mysqld.*errno'
这显示了：
/usr/bin/mysqld_safe_helper: Cannot change uid/gid (errno: 1)
以下这篇文章似乎已经修复了该问题，该问题与 MariaDB 10.0.XX 版本和 SELinux 有关：
https://www.penguinprompt.com/mariadb-10-0-29-update-failure-selinux/
我可以启动 mysql 服务并配置它mysql_secure_installation
答案2
我想我应该检查 mariadb-server 是否正确安装 - 它似乎包含服务定义：
rpm -qvla mariadb-server | grep service
-rw-r--r-- 1 root root 1697 Nov 14 16:44 /usr/lib/systemd/system/mariadb.service
你也可以使用 yum 检查：
> yum info mariadb-server
Loaded plugins: fastestmirror, ovl
Loading mirror speeds from cached hostfile
* base: centos.mirror.triple-it.nl
* extras: centos.mirror.transip.nl
* updates: centos.ams.host-engine.com
Installed Packages
Name : mariadb-server
Arch : x86_64
Epoch : 1
Version : 5.5.52
Release : 1.el7
Size : 56 M
Repo : installed
您正在寻找上面的最后一行来表示installed，而不是base/7/x86_64。
我刚刚在全新的 centos7 映像（官方 centos docker 容器）上尝试了您的安装命令，但无法重现您的问题。
您可能需要尝试重新安装 mariadb-server。
更新：我认为您的问题是由于您的 MariaDB 软件包来自 webmin 存储库，而不是基础存储库。暂时（或永久）禁用它可能会有所帮助：sudo yum install --disablerepo=Webmin mariadb-server应该可以解决您的当前问题（和/或让您获得所需的文件）。
所有其他的都失败了，服务定义非常简单：
# It's not recommended to modify this file in-place, because it will be
# overwritten during package upgrades. If you want to customize, the
# best way is to create a file "/etc/systemd/system/mariadb.service",
# containing
# .include /lib/systemd/system/mariadb.service
# ...make your changes here...
# or create a file "/etc/systemd/system/mariadb.service.d/foo.conf",
# which doesn't need to include ".include" call and which will be parsed
# after the file mariadb.service itself is parsed.
#
# For more info about custom unit files, see systemd.unit(5) or
# http://fedoraproject.org/wiki/Systemd#How_do_I_customize_a_unit_file.2F_add_a_custom_unit_file.3F
# For example, if you want to increase mariadb's open-files-limit to 10000,
# you need to increase systemd's LimitNOFILE setting, so create a file named
# "/etc/systemd/system/mariadb.service.d/limits.conf" containing:
# [Service]
# LimitNOFILE=10000
# Note: /usr/lib/... is recommended in the .include line though /lib/...
# still works.
# Don't forget to reload systemd daemon after you change unit configuration:
# root> systemctl --system daemon-reload
[Unit]
Description=MariaDB database server
After=syslog.target
After=network.target
[Service]
Type=simple
User=mysql
Group=mysql
ExecStartPre=/usr/libexec/mariadb-prepare-db-dir %n
# Note: we set --basedir to prevent probes that might trigger SELinux alarms,
# per bug #547485
ExecStart=/usr/bin/mysqld_safe --basedir=/usr
ExecStartPost=/usr/libexec/mariadb-wait-ready $MAINPID
# Give a reasonable amount of time for the server to start up/shut down
TimeoutSec=300
# Place temp files in a secure directory, not /tmp
PrivateTmp=true
[Install]
WantedBy=multi-user.target
答案3
我也遇到了同样的问题。我的解决方案是：sudo systemctl start mysql.service和sudo chkconfig mysql on。
也许你应该暂时禁用 SeLinux：sudo setenforce 0
问候