Gfilui

I am running MySQL 5.7.19, under LAMP, on two Ubuntu 16.04. This is an AWS EC2 instance.

It is some time since I installed MySQL and I have not used it so it would not be a problem if I reinstalled it. Nothing I enter for the root password works.

I tried

 sudo /etc/init.d/mysql stop
 sudo /usr/sbin/mysqld --skip-grant-tables --skip-networking &
sudo mysql -u root

Resulted in

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

I then tried the procedure outlined here. When I entered

 sudo apt-get install mysql-server

I got

Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 linux-headers-generic : Depends: linux-headers-4.4.0-119-generic but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

When I enter

ps -aux | grep mysql

the result is

ubuntu 27152 0.0 0.0 12948 984 pts/1 S+ 12:30 0:00 grep --color=auto mysql

When I enter

 mysql -u root -p

I get

Enter password:

So mysql has not been uninstalled and I cannot reconfigure it.

Update 1:

When I ran

sudo dpkg-reconfigure mysql-server-5.7

I got

update-alternatives: warning: forcing reinstallation of alternative 
/etc/mysql/mysql.cnf because link group my.cnf is broken
update-alternatives: warning: not replacing /etc/mysql/my.cnf with a link
mysql_upgrade: [ERROR] unknown option '--~'
Upgrade process encountered error and will not continue.

 mysql -u root -p

results in

Enter password:
ERROR 1698 (28000): Access denied for user 'root'@'localhost'

Edit 2

I tried the following with the associated results.

ubuntu@ip-10-0-1-73:~$ sudo apt autoremove --purge mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 linux-headers-generic : Depends: linux-headers-4.4.0-119-generic but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).
ubuntu@ip-10-0-1-73:~$ sudo apt install mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 linux-headers-generic : Depends: linux-headers-4.4.0-119-generic but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

Running

apt-get -f install

did not change anything.

Edit 3:

If I use

sudo mysql -u root

it take me into mysql. If I use the -p switch, it accepts anything as a password. However, when I enter

mysql> UPDATE mysql.user SET authentication_string=PASSWORD('newPassword') WHERE User='root';

I get

Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 1

Warning (Code 1681): 'PASSWORD' is deprecated and will be removed in a future release.

I then entered

FLUSH PRIVILEGES;

and got the following message

Query OK, 0 rows affected (0.00 sec)

I then quit and still get the same result if I do not use sudo

 mysql -u root -p
Enter password:
ERROR 1698 (28000): Access denied for user 'root'@'localhost'

Edit 4:

I tried the following with the ensuing results.

$ sudo apt install linux-headers-4.4.0-119-generic
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 linux-headers-4.4.0-119-generic : Depends: linux-headers-4.4.0-119 but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).
ubuntu@ip-10-0-1-73:~$ sudo apt-get -f install linux-headers-4.4.0-119- generic
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 linux-headers-4.4.0-119-generic : Depends: linux-headers-4.4.0-119 but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).
$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
 linux-headers-4.4.0-64 linux-headers-4.4.0-64-generic linux-headers-4.4.0- 66 linux-headers-4.4.0-66-generic linux-headers-4.4.0-70 linux-headers-4.4.0-70-generic
 linux-headers-4.4.0-71 linux-headers-4.4.0-71-generic linux-headers-4.4.0- 72 linux-headers-4.4.0-72-generic linux-headers-4.4.0-75 linux-headers-4.4.0-75- generic
 linux-headers-4.4.0-78 linux-headers-4.4.0-78-generic linux-headers-4.4.0- 79 linux-headers-4.4.0-79-generic linux-headers-4.4.0-81 linux-headers-4.4.0-81-generic
 linux-headers-4.4.0-83 linux-headers-4.4.0-83-generic linux-headers-4.4.0-87 linux-headers-4.4.0-87-generic linux-headers-4.4.0-89 linux-headers-4.4.0-89-generic
 linux-headers-4.4.0-91 linux-headers-4.4.0-91-generic linux-headers-4.4.0-92 linux-headers-4.4.0-92-generic linux-image-4.4.0-112-generic
 linux-image-4.4.0-64-generic linux-image-4.4.0-66-generic linux-image- 4.4.0-70-generic linux-image-4.4.0-71-generic linux-image-4.4.0-72-generic
 linux-image-4.4.0-75-generic linux-image-4.4.0-78-generic linux-image-4.4.0-79-generic linux-image-4.4.0-81-generic linux-image-4.4.0-83-generic
 linux-image-4.4.0-87-generic linux-image-4.4.0-89-generic linux-image-4.4.0-91-generic linux-image-4.4.0-92-generic linux-image-4.4.0-97-generic
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
 linux-headers-4.4.0-119 linux-headers-4.4.0-119-generic
The following NEW packages will be installed:
 linux-headers-4.4.0-119 linux-headers-4.4.0-119-generic
0 upgraded, 2 newly installed, 0 to remove and 224 not upgraded.
10 not fully installed or removed.
Need to get 0 B/10.8 MB of archives.
After this operation, 78.3 MB of additional disk space will be used.
Do you want to continue? [Y/n]
(Reading database ... 512472 files and directories currently installed.)
Preparing to unpack .../linux-headers-4.4.0-119_4.4.0-119.143_all.deb ...
Unpacking linux-headers-4.4.0-119 (4.4.0-119.143) ...
dpkg: error processing archive /var/cache/apt/archives/linux-headers-4.4.0- 119_4.4.0-119.143_all.deb (--unpack):
 unable to create '/usr/src/linux-headers-4.4.0- 119/include/linux/cpufeature.h.dpkg-new' (while processing './usr/src/linux- headers-4.4.0-119/include/linux/cpufeature.h'): No space left on device
No apport report written because the error message indicates a disk full error
 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Preparing to unpack .../linux-headers-4.4.0-119-generic_4.4.0- 119.143_amd64.deb ...
Unpacking linux-headers-4.4.0-119-generic (4.4.0-119.143) ...
dpkg: error processing archive /var/cache/apt/archives/linux-headers-4.4.0- 119-generic_4.4.0-119.143_amd64.deb (--unpack):
 unable to create '/usr/src/linux-headers-4.4.0-119- generic/include/config/rtc/drv/88pm860x.h.dpkg-new' (while processing './usr/src/linux-headers-4.4.0-119-generic/include/config/rtc/drv/88pm860x.h'): No space left on device
No apport report written because the error message indicates a disk full error
 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Errors were encountered while processing:
 /var/cache/apt/archives/linux-headers-4.4.0-119_4.4.0-119.143_all.deb
 /var/cache/apt/archives/linux-headers-4.4.0-119-generic_4.4.0- 119.143_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

$df
Filesystem 1K-blocks Used Available Use% Mounted on
udev 498080 0 498080 0% /dev
tmpfs 101440 12068 89372 12% /run
/dev/xvda1 8117828 5515716 2166836 72% /
tmpfs 507184 0 507184 0% /dev/shm
tmpfs 5120 0 5120 0% /run/lock
tmpfs 507184 0 507184 0% /sys/fs/cgroup
tmpfs 101444 0 101444 0% /run/user/1000

To reset MySQL passord please follow the procedure from "B.5.3.2.2 Resetting the Root Password: Unix and Unix-Like Systems":

Stop the MySQL server by sending a normal kill (not kill -9) to the
mysqld process. Use the actual path name of the .pid file in the
following command:

kill `cat /mysql-data-directory/host_name.pid`

Use backticks (not forward quotation marks) with the cat command.
These cause the output of cat to be substituted into the kill command.

Create a text file containing the password-assignment statement on a
single line. Replace the password with the password that you want to
use.

ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';

Save the file. This example assumes that you name the file
/home/me/mysql-init. The file contains the password, so do not save it
where it can be read by other users. If you are not logged in as mysql
(the user the server runs as), make sure that the file has permissions
that permit mysql to read it.

Start the MySQL server with the special --init-file option:

mysqld --init-file=/home/me/mysql-init &

The server executes the contents of the file named by the --init-file
option at startup, changing the 'root'@'localhost' account password.

Other options may be necessary as well, depending on how you normally
start your server. For example, --defaults-file may be needed before
--init-file.

After the server has started successfully, delete /home/me/mysql-init.

First, let's fix your package manager problem. Install the missing dependencies using:

sudo apt install -f

After that, if you had already uninstalled mysql-server, please reinstall it:

sudo apt install mysql-server

If you didn't uninstall it yet, or if reinstalling it did not prompt you for a new MySQL root password, now run (adapting the version number if necessary):

sudo dpkg-reconfigure mysql-server-5.7

That should have reset your password by now. Try logging in again as root with interactive password prompt:

mysql -u root -p

If you still get the error

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

that most likely means that the MySQL server is not running. Try starting it with:

sudo systemctl restart mysql

After that, systemctl status mysql should report it as "active(running)". Try logging in again then.

Finally sorted it out.

First, found and remove all instances of my.cnf.bak. Also removed /etc/alternatives/my.cnf, /var/lib/dpkg/alternatives/my.cnf and /etc/mysql/conf.d (but backed them up). Then

sudo apt-get remove --purge mysql-*
sudo apt-get install mysql-server mysql-client

If you still get something like

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

this is often resolved with

sudo service mysql start