Troubleshoot SQL Server on Linux

THIS TOPIC APPLIES TO: yesSQL Server (Linux only)noAzure SQL DatabasenoAzure SQL Data WarehousenoParallel Data Warehouse

This document describes how to troubleshoot Microsoft SQL Server running on Linux or in a Docker container. When troubleshooting SQL Server on Linux, please remember to review the supported features and known limitations in the SQL Server on Linux Release Notes.

Troubleshoot connection failures

If you are having difficulty connecting to your Linux SQL Server, there are a few things to check.

  • Verify that the server name or IP address is reachable from your client machine.


    To find the IP address of your Ubuntu machine, you can run the ifconfig command as in the following example:

    sudo ifconfig eth0 | grep 'inet addr'

    For Red Hat, you can use the ip addr as in the following example:

    sudo ip addr show eth0 | grep "inet"

    One exception to this technique relates to Azure VMs. For Azure VMs, find the public IP for the VM in the Azure portal.

  • If applicable, check that you have opened the SQL Server port (default 1433) on the firewall.

  • For Azure VMs, check that you have a network security group rule for the default SQL Server port.

  • Verify that the user name and password do not contain any typos or extra spaces or incorrect casing.

  • Try to explicitly set the protocol and port number with the server name like the following: tcp:servername,1433.

  • Network connectivity issues can also cause connection errors and timeouts. After verifying your connection information and network connectivity, try the connection again.

Manage the SQL Server service

The following sections show how to start, stop, restart, and check the status of the SQL Server service.

Manage the mssql-server service in Red Hat Enterprise Linux (RHEL) and Ubuntu

Check the status of the status of the SQL Server service using this command:

sudo systemctl status mssql-server

You can stop, start, or restart the SQL Server service as needed using the following commands:

sudo systemctl stop mssql-server
sudo systemctl start mssql-server
sudo systemctl restart mssql-server

Manage the execution of the mssql Docker container

You can get the status and container ID of the latest created SQL Server Docker container by running the following command (The ID will be under the “CONTAINER ID” column):

sudo docker ps -l

You can stop or restart the SQL Server service as needed using the following commands:

sudo docker stop <container ID>
sudo docker restart <container ID>


For more troubleshooting tips for Docker, see Troubleshooting SQL Server Docker containers.

Access the log files

The SQL Server engine logs to the /var/opt/mssql/log/errorlog file in both the Linux and Docker installations. You need to be in ‘superuser’ mode to browse this directory.

The installer logs here: /var/opt/mssql/setup-< time stamp representing time of install> You can browse the errorlog files with any UTF-16 compatible tool like ‘vim’ or ‘cat’ like this:

sudo cat errorlog

If you prefer, you can also convert the files to UTF-8 to read them with ‘more’ or ‘less’ with the following command:

sudo iconv –f UTF-16LE –t UTF-8 <errorlog> -o <output errorlog file>

Extended events

Extended events can be queried via a SQL command. More information about extended events can be found here:

Crash dumps

Look for dumps in the log directory in Linux. Check under the /var/opt/mssql/log directory for Linux Core dumps (.tar.gz2 extension) or SQL minidumps (.mdmp extension)

For Core dumps

sudo ls /var/opt/mssql/log | grep .tar.gz2 

For SQL dumps

sudo ls /var/opt/mssql/log | grep .mdmp 

Start SQL Server in Minimal Configuration or in Single User Mode

Start SQL Server in Minimal Configuration Mode

This is useful if the setting of a configuration value (for example, over-committing memory) has prevented the server from starting.

sudo -u mssql /opt/mssql/bin/sqlservr -f

Start SQL Server in Single User Mode

Under certain circumstances, you may have to start an instance of SQL Server in single-user mode by using the startup option -m. For example, you may want to change server configuration options or recover a damaged master database or other system database. For example, you may want to change server configuration options or recover a damaged master database or other system database

Start SQL Server in Single User Mode

sudo -u mssql /opt/mssql/bin/sqlservr -m

Start SQL Server in Single User Mode with SQLCMD

sudo -u mssql /opt/mssql/bin/sqlservr -m SQLCMD


Start SQL Server on Linux with the "mssql" user to prevent future startup issues. Example "sudo -u mssql /opt/mssql/bin/sqlservr [STARTUP OPTIONS]"

If you have accidentally started SQL Server with another user, you will need to change ownership of SQL Server database files back to the 'mssql' user prior to starting SQL Server with systemd. For example, to change ownership of all database files under /var/opt/mssql to the 'mssql' user, run the following command

chown -R mssql:mssql /var/opt/mssql/

Common issues

  1. You can not connect to your remote SQL Server instance.

    See the troubleshooting section of the topic, Connect to SQL Server on Linux.

  2. ERROR: Hostname must be 15 characters or less.

    This is a known-issue that happens whenever the name of the machine that is trying to install the SQL Server Debian package is longer than 15 characters. There are currently no workarounds other than changing the name of the machine. One way to achieve this is by editing the hostname file and rebooting the machine. The following website guide explains this in detail.

  3. Resetting the system administration (SA) password.

    If you have forgotten the system administrator (SA) password or need to reset it for some other reason please follow these steps.


    Following these steps will stop the SQL Server service temporarily.

    Log into the host terminal, run the following commands and follow the prompts to reset the SA password:

    sudo systemctl stop mssql-server
    sudo /opt/mssql/bin/mssql-conf setup
  4. Using special characters in password.

    If you use some characters in the SQL Server login password you may need to escape them when using them in the Linux terminal. You will need to escape the $ anytime using the backslash character you are using it in a terminal command/shell script:

    Does not work:

    sudo sqlcmd -S myserver -U sa -P Test$$


    sqlcmd -S myserver -U sa -P Test\$\$

    Resources: Special characters Escaping


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