Can't reset root password with --skip-grant-tables on ubuntu 16

Question

I am trying to reset the root password following MysqlPasswordReset but when I try to start the server with --skip-grant-tables the server doesn't start

• Ubuntu 16.04.1 LTS (GNU/Linux 4.4.0-59-generic x86_64)
• mysql Ver 14.14 Distrib 5.7.17, for Linux (x86_64)

Server is running

$ mysql -u root
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

Stop server

$ sudo /etc/init.d/mysql stop
[ ok ] Stopping mysql (via systemctl): mysql.service.

Trying to start with --skip-grant-tables

sudo /usr/sbin/mysqld --skip-grant-tables --skip-networking &
[1] 9856

Connect with no password

$ mysql -u root
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
[1]+  Exit 1                  sudo /usr/sbin/mysqld --skip-grant-tables --skip-networking

I also tried to start with mysql_safe (error.log is empty)

sudo mysqld_safe --skip-grant-tables
2017-02-01T16:33:31.382105Z mysqld_safe Logging to syslog.
2017-02-01T16:33:31.383942Z mysqld_safe Logging to '/var/log/mysql/error.log'.
2017-02-01T16:33:31.386058Z mysqld_safe Logging to '/var/log/mysql/error.log'.
2017-02-01T16:33:31.388009Z mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists.

Answer 1

I found that the mysql.sock is deleted when the mysql service is stoped and mysqld_safe can't create it (I couldn't find the reason), so my solution was back up the sock folder and restore before start mysqld_safe

Start server

$ sudo service mysql start

Go to sock folder

$ cd /var/run

Back up the sock

$ sudo cp -rp ./mysqld ./mysqld.bak

Stop server

$ sudo service mysql stop

Restore the sock

$ sudo mv ./mysqld.bak ./mysqld

Start mysqld_safe

$ sudo mysqld_safe --skip-grant-tables --skip-networking &

Init mysql shell

mysql -u root

Change password

FLUSH PRIVILEGES;

SET PASSWORD FOR root@'localhost' = PASSWORD('my_new_password');