root@raspberrypi:/home/pi# apt install mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
  mysql-server
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
2 not fully installed or removed.
Need to get 0 B/1706 B of archives.
After this operation, 8192 B of additional disk space will be used.
apt-listchanges: Can't set locale; make sure $LC_* and $LANG are correct!
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
	LANGUAGE = (unset),
	LC_ALL = (unset),
	LC_TIME = "de_BE.UTF-8",
	LC_MONETARY = "de_BE.UTF-8",
	LC_ADDRESS = "de_BE.UTF-8",
	LC_TELEPHONE = "de_BE.UTF-8",
	LC_NAME = "de_BE.UTF-8",
	LC_MEASUREMENT = "de_BE.UTF-8",
	LC_IDENTIFICATION = "de_BE.UTF-8",
	LC_NUMERIC = "de_BE.UTF-8",
	LC_PAPER = "de_BE.UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
locale: Cannot set LC_ALL to default locale: No such file or directory
Selecting previously unselected package mysql-server.
(Reading database ... 124019 files and directories currently installed.)
Preparing to unpack .../mysql-server_5.5.9999+default_armhf.deb ...
Unpacking mysql-server (5.5.9999+default) ...
Setting up mariadb-server-10.1 (10.1.23-9+deb9u1) ...
locale: Cannot set LC_ALL to default locale: No such file or directory
Job for mariadb.service failed because the control process exited with error code.
See "systemctl status mariadb.service" and "journalctl -xe" for details.
invoke-rc.d: initscript mysql, action "start" failed.
● mariadb.service - MariaDB database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sun 2018-06-24 14:56:15 UTC; 210ms ago
  Process: 17979 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=1/FAILURE)
  Process: 17890 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ]   && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1 (code=exited, status=0/SUCCESS)
  Process: 17886 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 17883 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
 Main PID: 17979 (code=exited, status=1/FAILURE)
   Status: "MariaDB server is down"

Jun 24 14:56:10 raspberrypi systemd[1]: Starting MariaDB database server...
Jun 24 14:56:12 raspberrypi mysqld[17979]: 2018-06-24 14:56:12 3069258960 [N…...
Jun 24 14:56:15 raspberrypi systemd[1]: mariadb.service: Main process exited…URE
Jun 24 14:56:15 raspberrypi systemd[1]: Failed to start MariaDB database server.
Jun 24 14:56:15 raspberrypi systemd[1]: mariadb.service: Unit entered failed…te.
Jun 24 14:56:15 raspberrypi systemd[1]: mariadb.service: Failed with result …e'.
Hint: Some lines were ellipsized, use -l to show in full.
dpkg: error processing package mariadb-server-10.1 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of default-mysql-server:
 default-mysql-server depends on mariadb-server-10.1; however:
  Package mariadb-server-10.1 is not configured yet.

dpkg: error processing package default-mysql-server (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of mysql-server:
 mysql-server depends on default-mysql-server; however:
  Package default-mysql-server is not configured yet.

dpkg: error processing package mysql-server (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 mariadb-server-10.1
 default-mysql-server
 mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@raspberrypi:/home/pi# cd
root@raspberrypi:~# sudo apt-get remove mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  default-mysql-server galera-3 libaio1 libcgi-fast-perl libcgi-pm-perl
  libdbd-mysql-perl libdbi-perl libencode-locale-perl libfcgi-perl
  libhtml-parser-perl libhtml-tagset-perl libhtml-template-perl
  libhttp-date-perl libhttp-message-perl libio-html-perl libjemalloc1
  liblwp-mediatypes-perl libmariadbclient18 libreadline5 libterm-readkey-perl
  libtimedate-perl liburi-perl mariadb-client-10.1 mariadb-client-core-10.1
  mariadb-common mariadb-server-10.1 mariadb-server-core-10.1 mysql-common
  socat
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  mysql-server
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
3 not fully installed or removed.
After this operation, 8192 B disk space will be freed.
Do you want to continue? [Y/n] y
apt-listchanges: Can't set locale; make sure $LC_* and $LANG are correct!
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
	LANGUAGE = (unset),
	LC_ALL = (unset),
	LC_TIME = "de_BE.UTF-8",
	LC_MONETARY = "de_BE.UTF-8",
	LC_ADDRESS = "de_BE.UTF-8",
	LC_TELEPHONE = "de_BE.UTF-8",
	LC_NAME = "de_BE.UTF-8",
	LC_MEASUREMENT = "de_BE.UTF-8",
	LC_IDENTIFICATION = "de_BE.UTF-8",
	LC_NUMERIC = "de_BE.UTF-8",
	LC_PAPER = "de_BE.UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
locale: Cannot set LC_ALL to default locale: No such file or directory
(Reading database ... 124022 files and directories currently installed.)
Removing mysql-server (5.5.9999+default) ...
Setting up mariadb-server-10.1 (10.1.23-9+deb9u1) ...
locale: Cannot set LC_ALL to default locale: No such file or directory
Job for mariadb.service failed because the control process exited with error code.
See "systemctl status mariadb.service" and "journalctl -xe" for details.
invoke-rc.d: initscript mysql, action "start" failed.
● mariadb.service - MariaDB database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sun 2018-06-24 14:58:42 UTC; 314ms ago
  Process: 18412 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=1/FAILURE)
  Process: 18323 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ]   && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1 (code=exited, status=0/SUCCESS)
  Process: 18319 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 18316 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
 Main PID: 18412 (code=exited, status=1/FAILURE)
   Status: "MariaDB server is down"

Jun 24 14:58:37 raspberrypi systemd[1]: Starting MariaDB database server...
Jun 24 14:58:39 raspberrypi mysqld[18412]: 2018-06-24 14:58:39 3069951184 [N…...
Jun 24 14:58:42 raspberrypi systemd[1]: mariadb.service: Main process exited…URE
Jun 24 14:58:42 raspberrypi systemd[1]: Failed to start MariaDB database server.
Jun 24 14:58:42 raspberrypi systemd[1]: mariadb.service: Unit entered failed…te.
Jun 24 14:58:42 raspberrypi systemd[1]: mariadb.service: Failed with result …e'.
Hint: Some lines were ellipsized, use -l to show in full.
dpkg: error processing package mariadb-server-10.1 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of default-mysql-server:
 default-mysql-server depends on mariadb-server-10.1; however:
  Package mariadb-server-10.1 is not configured yet.

dpkg: error processing package default-mysql-server (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 mariadb-server-10.1
 default-mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@raspberrypi:~# apt-get --purge remove mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package 'mysql-server' is not installed, so not removed
The following packages were automatically installed and are no longer required:
  default-mysql-server galera-3 libaio1 libcgi-fast-perl libcgi-pm-perl
  libdbd-mysql-perl libdbi-perl libencode-locale-perl libfcgi-perl
  libhtml-parser-perl libhtml-tagset-perl libhtml-template-perl
  libhttp-date-perl libhttp-message-perl libio-html-perl libjemalloc1
  liblwp-mediatypes-perl libmariadbclient18 libreadline5 libterm-readkey-perl
  libtimedate-perl liburi-perl mariadb-client-10.1 mariadb-client-core-10.1
  mariadb-common mariadb-server-10.1 mariadb-server-core-10.1 mysql-common
  socat
Use 'apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
apt-listchanges: Can't set locale; make sure $LC_* and $LANG are correct!
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
	LANGUAGE = (unset),
	LC_ALL = (unset),
	LC_TIME = "de_BE.UTF-8",
	LC_MONETARY = "de_BE.UTF-8",
	LC_ADDRESS = "de_BE.UTF-8",
	LC_TELEPHONE = "de_BE.UTF-8",
	LC_NAME = "de_BE.UTF-8",
	LC_MEASUREMENT = "de_BE.UTF-8",
	LC_IDENTIFICATION = "de_BE.UTF-8",
	LC_NUMERIC = "de_BE.UTF-8",
	LC_PAPER = "de_BE.UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
locale: Cannot set LC_ALL to default locale: No such file or directory
Setting up mariadb-server-10.1 (10.1.23-9+deb9u1) ...
locale: Cannot set LC_ALL to default locale: No such file or directory
Job for mariadb.service failed because the control process exited with error code.
See "systemctl status mariadb.service" and "journalctl -xe" for details.
invoke-rc.d: initscript mysql, action "start" failed.
● mariadb.service - MariaDB database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sun 2018-06-24 15:01:24 UTC; 223ms ago
  Process: 18806 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=1/FAILURE)
  Process: 18717 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR=`/usr/bin/galera_recovery`; [ $? -eq 0 ]   && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1 (code=exited, status=0/SUCCESS)
  Process: 18712 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 18709 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
 Main PID: 18806 (code=exited, status=1/FAILURE)
   Status: "MariaDB server is down"

Jun 24 15:01:19 raspberrypi systemd[1]: Starting MariaDB database server...
Jun 24 15:01:21 raspberrypi mysqld[18806]: 2018-06-24 15:01:21 3069680848 [N…...
Jun 24 15:01:24 raspberrypi systemd[1]: mariadb.service: Main process exited…URE
Jun 24 15:01:25 raspberrypi systemd[1]: Failed to start MariaDB database server.
Jun 24 15:01:25 raspberrypi systemd[1]: mariadb.service: Unit entered failed…te.
Jun 24 15:01:25 raspberrypi systemd[1]: mariadb.service: Failed with result …e'.
Hint: Some lines were ellipsized, use -l to show in full.
dpkg: error processing package mariadb-server-10.1 (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of default-mysql-server:
 default-mysql-server depends on mariadb-server-10.1; however:
  Package mariadb-server-10.1 is not configured yet.

dpkg: error processing package default-mysql-server (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 mariadb-server-10.1
 default-mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@raspberrypi:~# ^C
root@raspberrypi:~#