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# Database Configuration

Nextcloud requires a database in which administrative data is stored. The following databases are currently supported:

- MySQL / MariaDB
- PostgreSQL
- Oracle

The MySQL or MariaDB databases are the recommended database engines.

## Requirements

Choosing to use MySQL / MariaDB, PostgreSQL, or Oracle as your database requires that you install and set up the server software first.

Note

The steps for configuring a third party database are beyond the scope of this document. Please refer to the documentation for your specific database choice for instructions.

### MySQL / MariaDB with Binary Logging Enabled

Nextcloud is currently using a `TRANSACTION_READ_COMMITTED` transaction isolation to avoid data loss under high load scenarios (e.g. by using the sync client with many clients/users and many parallel operations). This requires a disabled or correctly configured binary logging when using MySQL or MariaDB. Your system is affected if you see the following in your log file during the installation or update of Nextcloud:

> An unhandled exception has been thrown: exception ‘PDOException’ with message ‘SQLSTATE[HY000]: General error: 1665 Cannot execute statement: impossible to write to binary log since BINLOG_FORMAT = STATEMENT and at least one table uses a storage engine limited to row-based logging. InnoDB is limited to row-logging when transaction isolation level is READ COMMITTED or READ UNCOMMITTED.’

There are two solutions. One is to disable binary logging. Binary logging records all changes to your database, and how long each change took. The purpose of binary logging is to enable replication and to support backup operations.

The other is to change the BINLOG_FORMAT = STATEMENT in your database configuration file, or possibly in your database startup script, to BINLOG_FORMAT = MIXED. See Overview of the Binary Log and The Binary Log for detailed information.

### Database “READ COMMITED” transaction isolation level

As discussed above Nextcloud is using the `TRANSACTION_READ_COMMITTED` transaction isolation level. Some database configurations are enforcing other transaction isolation levels. To avoid data loss under high load scenarios (e.g. by using the sync client with many clients/users and many parallel operations) you need to configure the transaction isolation level accordingly. Please refer to the MySQL manual for detailed information.

## Parameters

For setting up Nextcloud to use any database, use the instructions in Installation Wizard. You should not have to edit the respective values in the `config/config.php`. However, in special cases (for example, if you want to connect your Nextcloud instance to a database created by a previous installation of Nextcloud), some modification might be required.

### Configuring a MySQL or MariaDB Database

If you decide to use a MySQL or MariaDB database, ensure the following:

- That you have installed and enabled the pdo_mysql extension in PHP
- That the mysql.default_socket points to the correct socket (if the database runs on the same server as Nextcloud).

Note

MariaDB is backwards compatible with MySQL. All instructions work for both. You will not need to replace mysql with anything.

The PHP configuration in `/etc/php5/conf.d/mysql.ini` could look like this:

    # configuration for PHP MySQL module
    extension=pdo_mysql.so

    [mysql]
    mysql.allow_local_infile=On
    mysql.allow_persistent=On
    mysql.cache_size=2000
    mysql.max_persistent=-1
    mysql.max_links=-1
    mysql.default_port=
    mysql.default_socket=/var/lib/mysql/mysql.sock  # Debian squeeze: /var/run/mysqld/mysqld.sock
    mysql.default_host=
    mysql.default_user=
    mysql.default_password=
    mysql.connect_timeout=60
    mysql.trace_mode=Off

Now you need to create a database user and the database itself by using the MySQL command line interface. The database tables will be created by Nextcloud when you login for the first time.

To start the MySQL command line mode use:

    mysql -uroot -p

Then a mysql> or MariaDB [root]> prompt will appear. Now enter the following lines and confirm them with the enter key:

    CREATE USER 'username'@'localhost' IDENTIFIED BY 'password';
    CREATE DATABASE IF NOT EXISTS nextcloud;
    GRANT ALL PRIVILEGES ON nextcloud.* TO 'username'@'localhost' IDENTIFIED BY 'password';

You can quit the prompt by entering:

    quit

An Nextcloud instance configured with MySQL would contain the hostname on which the database is running, a valid username and password to access it, and the name of the database. The `config/config.php` as created by the Installation Wizard would therefore contain entries like this:

    <?php

      "dbtype"        => "mysql",
      "dbname"        => "nextcloud",
      "dbuser"        => "username",
      "dbpassword"    => "password",
      "dbhost"        => "localhost",
      "dbtableprefix" => "oc_",

### PostgreSQL Database

If you decide to use a PostgreSQL database make sure that you have installed and enabled the PostgreSQL extension in PHP. The PHP configuration in `/etc/php5/conf.d/pgsql.ini` could look like this:

    # configuration for PHP PostgreSQL module
    extension=pdo_pgsql.so
    extension=pgsql.so

    [PostgresSQL]
    pgsql.allow_persistent = On
    pgsql.auto_reset_persistent = Off
    pgsql.max_persistent = -1
    pgsql.max_links = -1
    pgsql.ignore_notice = 0
    pgsql.log_notice = 0

The default configuration for PostgreSQL (at least in Ubuntu 14.04) is to use the peer authentication method. Check `/etc/postgresql/9.3/main/pg_hba.conf` to find out which authentication method is used in your setup. To start the postgres command line mode use:

    sudo -u postgres psql -d template1

Then a template1=# prompt will appear. Now enter the following lines and confirm them with the enter key:

    CREATE USER username CREATEDB;
    CREATE DATABASE nextcloud OWNER username;

You can quit the prompt by entering:

    \q

An Nextcloud instance configured with PostgreSQL would contain the path to the socket on which the database is running as the hostname, the system username the PHP process is using, and an empty password to access it, and the name of the database. The `config/config.php` as created by the Installation Wizard would therefore contain entries like this:

    <?php

      "dbtype"        => "pgsql",
      "dbname"        => "nextcloud",
      "dbuser"        => "username",
      "dbpassword"    => "",
      "dbhost"        => "/var/run/postgresql",
      "dbtableprefix" => "oc_",

Note

The host actually points to the socket that is used to connect to the database. Using localhost here will not work if postgreSQL is configured to use peer authentication. Also note, that no password is specified, because this authentication method doesn’t use a password.

If you use another authentication method (not peer), you’ll need to use the following steps to get the database setup: Now you need to create a database user and the database itself by using the PostgreSQL command line interface. The database tables will be created by Nextcloud when you login for the first time.

To start the postgres command line mode use:

    psql -hlocalhost -Upostgres

Then a postgres=# prompt will appear. Now enter the following lines and confirm them with the enter key:

    CREATE USER username WITH PASSWORD 'password';
    CREATE DATABASE nextcloud TEMPLATE template0 ENCODING 'UNICODE';
    ALTER DATABASE nextcloud OWNER TO username;
    GRANT ALL PRIVILEGES ON DATABASE nextcloud TO username;

You can quit the prompt by entering:

    \q

An Nextcloud instance configured with PostgreSQL would contain the hostname on which the database is running, a valid username and password to access it, and the name of the database. The `config/config.php` as created by the Installation Wizard would therefore contain entries like this:

    <?php

      "dbtype"        => "pgsql",
      "dbname"        => "nextcloud",
      "dbuser"        => "username",
      "dbpassword"    => "password",
      "dbhost"        => "localhost",
      "dbtableprefix" => "oc_",

## Troubleshooting

### How to workaround General error: 2006 MySQL server has gone away

The database request takes too long and therefore the MySQL server times out. Its also possible that the server is dropping a packet that is too large. Please refer to the manual of your database for how to raise the configuration options `wait_timeout` and/or `max_allowed_packet`.

Some shared hosters are not allowing the access to these config options. For such systems Nextcloud is providing a `dbdriveroptions` configuration option within your `config/config.php` where you can pass such options to the database driver. Please refer to Config.php Parameters for an example.

### How can I find out if my MySQL/PostgreSQL server is reachable?

To check the server’s network availability, use the ping command on the server’s host name (db.server.com in this example):

    ping db.server.dom

    PING db.server.dom (ip-address) 56(84) bytes of data.
    64 bytes from your-server.local.lan (192.168.1.10): icmp_req=1 ttl=64 time=3.64 ms
    64 bytes from your-server.local.lan (192.168.1.10): icmp_req=2 ttl=64 time=0.055 ms
    64 bytes from your-server.local.lan (192.168.1.10): icmp_req=3 ttl=64 time=0.062 ms

For a more detailed check whether the access to the database server software itself works correctly, see the next question.

### How can I find out if a created user can access a database?

The easiest way to test if a database can be accessed is by starting the command line interface:

MySQL:

Assuming the database server is installed on the same system you’re running the command from, use:

    mysql -uUSERNAME -p

To access a MySQL installation on a different machine, add the -h option with the respective host name:

    mysql -uUSERNAME -p -h HOSTNAME

    mysql> SHOW VARIABLES LIKE "version";
    +---------------+--------+
    | Variable_name | Value  |
    +---------------+--------+
    | version       | 5.1.67 |
    +---------------+--------+
    1 row in set (0.00 sec)
    mysql> quit

PostgreSQL:

Assuming the database server is installed on the same system you’re running the command from, use:

    psql -Uusername -dnextcloud

To access a MySQL installation on a different machine, add the -h option with the respective host name:

    psql -Uusername -dnextcloud -h HOSTNAME

    postgres=# SELECT version();
    PostgreSQL 8.4.12 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 4.1.3 20080704 (prerelease), 32-bit
    (1 row)
    postgres=# \q

### Useful SQL commands

Show Database Users:

    MySQL     : SELECT User,Host FROM mysql.user;
    PostgreSQL: SELECT * FROM pg_user;

Show available Databases:

    MySQL     : SHOW DATABASES;
    PostgreSQL: \l

Show Nextcloud Tables in Database:

    MySQL     : USE nextcloud; SHOW TABLES;
    PostgreSQL: \c nextcloud; \d

Quit Database:

    MySQL     : quit
    PostgreSQL: \q

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