Did you have on this machine 10.1 MariaDB server installed from the Debian default repo before switching to 10.2?
no , it was fresh VPS . if i remove my old my.cnf file and install 10,2 it is installing . but without my.cnf how can i add replication and all other things?
If there was no MariaDB / MySQL before, how come you have an old my.cnf file?
And could you please attach this file that causes the trouble?
when i end up with this error , i uninstalled mariadb-server .but my.cnf was there inside /etc/mysql/. so i removed my.cnf . and re installed mariadb . it worked . It didnt create my.cnf automatically .
is there anything i should do ? please suggest me .Even i tried with reloading os in VPS . fresh debian installation . Again i tried fresh installation of mariadb -server . it shows unable to set root password.
I asked you if you had a 10.1 server, you said that no, you had a clean VPS. Now you are saying that you did have some mariadb-server which you uninstalled.
Please figure out which it is before trying things. If you had a mariadb/mysql server, even if you removed it, it's not a clean installation, unless you carefully purged all data, which you apparently didn't, since you still had at least a config to remove. If you have old data, authentication rules recorded there apply, and the result depends on what was there, which depends on what server was installed before.
If you want something resembling a clean installation,
1) run dpkg -l | grep -iE 'mysql|maria|galera|percona' and make sure there are no traces of MySQL, MariaDB or Percona server or client;
2) remove (recursively) all of /etc/mysql*, /var/lib/mysql, /var/log/mysql.
Then try to install.
Results are :
root@s:/# dpkg -l | grep -iE 'mysql|galera|maria|percona'
root@s:/# apt-get install mariadb-server
......
a window appeared for password , i typed 12345
again it said unable to set password for 'root' user
..........
[ERROR] InnoDB: The Auto-extending innodb_system data file './ibdata1' is of a different size 0 pages than specified in the .cnf file: initial 768 pages, max 0 (relevant if non-zero) pages!
[ERROR] InnoDB: Plugin initialization aborted with error Generic error
2017-11-16 8:16:38 139802988214144 [Note] InnoDB: Starting shutdown...
2017-11-16 8:16:38 139802988214144 [ERROR] Plugin 'InnoDB' init function returned error.
2017-11-16 8:16:38 139802988214144 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2017-11-16 8:16:38 139802988214144 [Note] Plugin 'FEEDBACK' is disabled.
ERROR: 1146 Table 'mysql.user' doesn't exist
2017-11-16 8:16:38 139802988214144 [ERROR] Aborting
Okay, I see.
After you got this error, without further uninstalling or removing anything, please find the option innodb_flush_method = O_DIRECT in your config files and comment it.
Then run sudo mysql_install_db.
And then try to start the server the way you would normally start it.
i commented out
innodb_flush_method = O_DIRECT inside my.cnf
root@s6:/etc/mysql# mysql_install_db
WARNING: The host 's6' could not be looked up with /usr/bin/resolveip.
This probably means that your libc libraries are not 100 % compatible
with this binary MariaDB version. The MariaDB daemon, mysqld, should work
normally with the exception that host name resolving will not work.
This means that you should use IP addresses instead of hostnames
when specifying MariaDB privileges !
Installing MariaDB/MySQL system tables in '/var/lib/mysql' ...
2017-11-16 8:52:50 140192713385856 [ERROR] InnoDB: The Auto-extending innodb_system data file './ibdata1' is of a different size 0 pages than specified in the .cnf file: initial 768 pages, max 0 (relevant if non-zero) pages!
2017-11-16 8:52:50 140192713385856 [ERROR] InnoDB: Plugin initialization aborted with error Generic error
2017-11-16 8:52:51 140192713385856 [ERROR] Plugin 'InnoDB' init function returned error.
2017-11-16 8:52:51 140192713385856 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2017-11-16 8:52:51 140192713385856 [ERROR] Unknown/unsupported storage engine: InnoDB
2017-11-16 8:52:51 140192713385856 [ERROR] Aborting
Installation of system tables failed! Examine the logs in
/var/lib/mysql for more information.
Okay, that's a bit confusing. Just in case the directory got damaged by the previous failed attempt, keep the option commented, and run
sudo rm -rf /var/lib/mysql/*
|
sudo mysql_install_db
|
If it doesn't work this way, then you probably have permission problems on /var/lib/mysql.
But if it helps and mysql_install_db works, please let us know what df -kT /var/lib/mysql say.
root@s6:/rm -rf /var/lib/mysql/*
root@s6:/mysql_install_db
root@s6:/systemctl status mariadb.service
root@s6:/var/lib/mysql# systemctl status mariadb.service
● mariadb.service - MariaDB database server
Loaded: loaded (/lib/systemd/system/mariadb.service; enabled)
Drop-In: /etc/systemd/system/mariadb.service.d
└─migrated-from-my.cnf-settings.conf
Active: active (running) since Thu 2017-11-16 10:49:48 CST; 39s ago
yes that worked 
root@s6:/var/lib/mysql# df -kT /var/lib/mysql
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/xvda2 ext3 102832424 1536596 96065492 2% /
Thank you
Thanks. ext3 confirms that you've encountered the bug MDEV-14244 . It's already fixed, the fix will be released with the next release 10.2.11.