ubuntu - mysql start and restart issue on ubuntu 16.04 server - mysql

Question

i installed mysql 5.7 but then found out I need mysql 5.6 so i deleted all mysql related packages with
apt-get remove --purge mysql*
so it gotten removed. then i issued:
apt-get install mysql-server-5.6 mysql-client-5.6
so the mentioned packages gotten installed.
but its not starting using systemctl start mysql or service mysql start or even restart. the result is this:
service mysql restart
or
service mysql start
or
systemctl restart mysql
or
systemctl start mysql
returns:
Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.
but
systemctl status mysql
returns
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'.
what is Failed to start LSB: Start and stop the mysql database server daemon.
before installing 5.6 the 5.7 version was working fine but now its like this.
the /var/log/mysql/errors.log is empty and these are the /var/log/syslog last lines
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'.
output of 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
and this is my /etc/mysql/my.cnf and there is no /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/

Answer 1

This problem arrives when your /etc/mysql/mysql.conf.d/mysqld.cnf file is wrongly set. If you recently made changes to this file please revert to the previous one or copy the default one here
#
# 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

Answer 2

Stop mysql service:
sudo service mysql stop
Remove mysql:
sudo apt-get remove mysql
sudo apt-get purge mysql
Then issue a whereis mysql command in terminal and remove all of the locations that command lists using rm -rf command. For example rm -rf /etc/mysql .
Then reinstall the version of mysql you desire. All should work as expected.

Answer 3

Just check if you db has been given the rights to write the logs give it the logs writing rights and this will get resolved .

Answer 4

1)First remove already installed mysql-server using--
sudo apt-get remove --purge mysql-server mysql-client mysql-common
2)Then clean all files
sudo apt-get autoremove
3)Then install mysql-server --
sudo apt-get remove -f mysql-server
4)Start mysql server--
sudo systemctl start mysql
5)Check status of mysql-server--
systemctl status mysql