Troubleshooting Connection Issues
If you are completely new to MariaDB and relational databases, you may want
to start with the MariaDB Primer. Also, make sure you understand the
connection parameters discussed in the Connecting to MariaDB article.

There are a number of common problems that can occur when connecting to
MariaDB.



Server Not Running in Specified Location
If the error you get is something like:
	mariadb -uname -p -uname -p
ERROR 2002 (HY000): Can't connect to local MySQL server through 
 socket '/var/run/mysqld/mysqld.sock' (2 "No such file or directory")

or
	mariadb -uname -p --port=3307 --protocol=tcp
ERROR 2003 (HY000): Can't connect to MySQL server on 'localhost' 
 (111 "Connection refused")

the server is either not running, or not running on the specified port,
socket or pipe. Make sure you are using the correct host, port, pipe, socket
and protocol options, or alternatively, see Getting, Installing and
Upgrading MariaDB, Starting and Stopping MariaDB or Troubleshooting
Installation Issues.

The socket file can be in a non-standard path. In this case, the socket
option is probably written in the my.cnf file. Check that its value is
identical in the [mysqld] and [client] sections; if not, the client will
look for a socket in a wrong place.

If unsure where the Unix socket file is running, it's possible to find this
out, for example:
	netstat -ln | grep mysqld
unix 2 [ ACC ] STREAM LISTENING 33209505 /var/run/mysqld/mysqld.sock



Unable to Connect from a Remote Location
Usually, the MariaDB server does not by default accept connections from a
remote client or connecting with tcp and a hostname and has to be configured
to permit these.
	(/my/maria-10.4) ./client/mysql --host=myhost --protocol=tcp --port=3306
test
ERROR 2002 (HY000): Can't connect to MySQL server on 'myhost' (115)
(/my/maria-10.4) telnet myhost 3306
Trying 192.168.0.11...
telnet: connect to address 192.168.0.11: Connection refused
(/my/maria-10.4) perror 115
OS error code 115: Operation now in progress

To solve this, see Configuring MariaDB for Remote Client Access



Authentication Problems
Note that from MariaDB 10.4.3, the unix_socket authentication plugin is
enabled by default on Unix-like systems. This uses operating system
credentials when connecting to MariaDB via the local Unix socket file. See
unix_socket authentication plugin for instructions on connecting and on
switching to password-based authentication as well as Authentication from
MariaDB 10.4 for an overview of the MariaDB 10.4 changes..

Authentication is granted to a particular username/host combination.
user1'@'localhost', for example, is not the same as user1'@'166.78.144.191'.
See the GRANT article for details on granting permissions.

Passwords are hashed with PASSWORD function. If you have set a password with
the SET PASSWORD statement, the PASSWORD function must be used at the same
time. For example, SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass')
rather than just SET PASSWORD FOR 'bob'@'%.loc.gov' = 'newpass';



Problems Exporting Query Results
If you can run regular queries, but get an authentication error when running
the SELECT ... INTO OUTFILE, SELECT ... INTO DUMPFILE or LOAD DATA INFILE
statements, you do not have permission to write files to the server. This
requires the FILE privilege. See the GRANT article.



Access to the Server, but not to a Database

If you can connect to the server, but not to a database, for example:
	USE test;
ERROR 1044 (42000): Access denied for user 'ian'@'localhost' to database
'test'

or can connect to a particular database, but not another, for example
mariadb -uname -p -u name db1 works but not mariadb -uname -p -u name db2,
you have not been granted permission for the particular database. See the
GRANT article.



Option Files and Environment Variables
It's possible that option files or environment variables may be providing
incorrect connection parameters. Check the values provided in any option
files read by the client you are using (see mysqld Configuration Files and
Groups and the documentation for the particular client you're using - see
Clients and Utilities).

Option files can usually be suppressed with no-defaults option, for
example:
	mariadb-import --no-defaults ... 



Unable to Connect to a Running Server 
/ Lost root Password
If you are unable to connect to a server, for example because you have lost
the root password, you can start the server without using the privilege
tables by running the --skip-grant-tables option, which gives users full
access to all tables. You can then run FLUSH PRIVILEGES to resume using the
grant tables, followed by SET PASSWORD to change the password for an
account.



localhost and %
You may have created a user with something like:
	CREATE USER melisa identified by 'password';

This creates a user with the '%' wildcard host.
	select user,host from mysql.user where user='melisa';
+--------+------+
| user | host |
+--------+------+
| melisa | % |
+--------+------+

However, you may still be failing to login from localhost. Some setups
create anonymous users, including localhost. So the following records exist
in the user table:

select user,host from mysql.user where user='melisa' or user='';
	+--------+-----------+
| user | host |
+--------+-----------+
| melisa | % |
| | localhost |
+--------+-----------+

Since you are connecting from localhost, the anonymous credentials, rather
than those for the 'melisa' user, are used. The solution is either to add a
new user specific to localhost, or to remove the anonymous localhost user.



See Also

CREATE USER
GRANT
Authentication from MariaDB 10.4
Authentication from MariaDB 10 4 video tutorial
Error 1698: Access denied for user