我安装了mysql 5.7但后来发现我需要mysql 5.6所以我删除了所有与mysql相关的包
apt-get remove --purge mysql*
所以它被删除了。然后我发了：
apt-get install mysql-server-5.6 mysql-client-5.6
所以提到的软件包已经安装好了。
但它没有开始使用systemctl start mysql或service mysql start甚至重新启动。结果是：
service mysql restart
or
service mysql start
or
systemctl restart mysql
or
systemctl start mysql
返回：
Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.
但
systemctl status mysql
返回
mysql.service - LSB: Start and stop the mysql database server daemon
Loaded: loaded (/etc/init.d/mysql; bad; vendor preset: enabled)
Active: failed (Result: exit-code) since Mon 2017-04-10 13:24:00 EDT; 29s ago
Docs: man:systemd-sysv-generator(8)
Process: 15820 ExecStart=/etc/init.d/mysql start (code=exited, status=1/FAILURE)
Main PID: 1323 (code=exited, status=0/SUCCESS)
Apr 10 13:23:30 server mysqld[15926]: 2017-04-10 13:23:30 15925 [Note] InnoDB: Compressed tables use zlib 1.2.8
Apr 10 13:23:30 server mysqld[15926]: 2017-04-10 13:23:30 15925 [Note] InnoDB: Using Linux native AIO
Apr 10 13:23:30 server mysqld[15926]: 2017-04-10 13:23:30 15925 [Note] InnoDB: Using CPU crc32 instructions
Apr 10 13:23:30 server mysqld[15926]: 2017-04-10 13:23:30 15925 [Note] InnoDB: Initializing buffer pool, size = 128.0M
Apr 10 13:23:30 server mysqld[15926]: 2017-04-10 13:23:30 15925 [Note] InnoDB: Completed initialization of buffer pool
Apr 10 13:24:00 server mysql[15820]: ...fail!
Apr 10 13:24:00 server systemd[1]: mysql.service: Control process exited, code=exited status=1
Apr 10 13:24:00 server systemd[1]: Failed to start LSB: Start and stop the mysql database server daemon.
Apr 10 13:24:00 server systemd[1]: mysql.service: Unit entered failed state.
Apr 10 13:24:00 server systemd[1]: mysql.service: Failed with result 'exit-code'.
什么是Failed to start LSB: Start and stop the mysql database server daemon.
在安装5.6之前，5.7版本工作正常，但现在就像这样。
/var/log/mysql/errors.log为空，这些是/var/log/syslog最后一行
Apr 10 13:23:30 server mysqld: 2017-04-10 13:23:30 15925 [Note] InnoDB: Completed initialization of buffer pool
Apr 10 13:23:30 server mysqld_safe: mysqld from pid file /var/lib/mysql/server.pid ended
Apr 10 13:24:00 server /etc/init.d/mysql[16277]: 0 processes alive and '/usr/bin/mysqladmin --defaults-file=/etc/mysql/debian.cnf ping' resulted in
Apr 10 13:24:00 server /etc/init.d/mysql[16277]: #007/usr/bin/mysqladmin: connect to server at 'localhost' failed
Apr 10 13:24:00 server /etc/init.d/mysql[16277]: error: 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)'
Apr 10 13:24:00 server /etc/init.d/mysql[16277]: Check that mysqld is running and that the socket: '/var/run/mysqld/mysqld.sock' exists!
Apr 10 13:24:00 server /etc/init.d/mysql[16277]:
Apr 10 13:24:00 server mysql[15820]: ...fail!
Apr 10 13:24:00 server systemd[1]: mysql.service: Control process exited, code=exited status=1
Apr 10 13:24:00 server systemd[1]: Failed to start LSB: Start and stop the mysql database server daemon.
Apr 10 13:24:00 server systemd[1]: mysql.service: Unit entered failed state.
Apr 10 13:24:00 server systemd[1]: mysql.service: Failed with result 'exit-code'.
mysqld_safe
170410 13:33:28 mysqld_safe Logging to syslog.
170410 13:33:28 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
170410 13:33:28 mysqld_safe mysqld from pid file /var/lib/mysql/server.pid ended
这是我的/etc/mysql/my.cnf，没有/etc/my.cnf
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# 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.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
# Here is entries for some specific programs
# The following values assume you have at least 32M ram
!includedir /etc/mysql/conf.d/
答案 0 :(得分：1)
当错误地设置了/etc/mysql/mysql.conf.d/mysqld.cnf文件时，就会出现此问题。如果您最近对此文件进行了更改，请还原为上一个文件或在此处复制默认文件
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# 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.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
# Here is entries for some specific programs
# The following values assume you have at least 32M ram
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
nice = 0
[mysqld]
#
# * Basic Settings
#
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address = 0.0.0.0
#
# * Fine Tuning
#
key_buffer_size = 16M
max_allowed_packet = 16M
thread_stack = 192K
thread_cache_size = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover-options = BACKUP
#max_connections = 100
#table_open_cache = 64
#thread_concurrency = 10
#
# * Query Cache Configuration
#
query_cache_limit = 1M
query_cache_size = 16M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file = /var/log/mysql/mysql.log
#general_log = 1
#
# Error log - should be very few entries.
#
log_error = /var/log/mysql/error.log
#
# Here you can see queries with especially long duration
#slow_query_log = 1
#slow_query_log_file = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
# other settings you may need to change.
#server-id = 1
#log_bin = /var/log/mysql/mysql-bin.log
#expire_logs_days = 10
max_binlog_size = 100M
#binlog_do_db = include_database_name
#binlog_ignore_db = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem
答案 1 :(得分：0)
停止mysql服务：
sudo service mysql stop
删除mysql：
sudo apt-get remove mysql
sudo apt-get purge mysql
然后在终端中发出whereis mysql命令，并使用rm -rf命令删除命令列表的所有位置。例如rm -rf /etc/mysql。
然后重新安装您想要的mysql版本。一切都应该按预期工作。
答案 2 :(得分：0)
只需检查您的数据库是否具有写日志的权限，再给它日志写权限，这将得到解决。
答案 3 :(得分：0)
1）首先使用-删除已经安装的mysql服务器 sudo apt-get remove --purge mysql-server mysql-client mysql-common
2）然后清理所有文件 sudo apt-get autoremove
3）然后安装mysql-server- sudo apt-get删除-f mysql-server
4）启动mysql服务器- sudo systemctl启动mysql
5）检查mysql服务器的状态- systemctl状态mysql