mssh

Open a new window and connect to multiple SSH servers

$ mssh [user@host1 user@host2 ...]

$ mssh [[-a|--alias]] [alias_name]

mssh [OPTIONS] {HOSTS | -f HOSTS_FILE} [--] COMMAND [ARGS...]

Examples:
mssh host1 host2 host3 -- uptime
mssh -f /path/to/hosts.txt -u myuser -- df -h

{HOSTS}
    A space-separated list of remote hostnames or IP addresses on which to execute the command.

-f {HOSTS_FILE}
    Specifies a file containing a list of remote hostnames or IP addresses, one per line.

-u {USER}
    The username to use for SSH authentication on remote hosts. If not specified, the current local username is often used.

-i {IDENTITY_FILE}
    Path to an SSH identity (private key) file for authentication.

-p {PORT}
    The SSH port number to connect to on remote hosts. Defaults to 22.

-P {PARALLELISM}
    Sets the maximum number of concurrent SSH connections to establish. This helps manage system load and network bandwidth.

--
    A mandatory separator used to distinguish mssh options from the command and its arguments to be executed on remote hosts.

{COMMAND}
    The command string to be executed on each remote host.

[ARGS...]
    Optional arguments for the COMMAND.

mssh, often an abbreviation for "Multi-SSH", refers to a class of utilities or custom scripts designed to run the same command on multiple remote Linux servers simultaneously via SSH. Unlike a single ssh command, mssh streamlines administrative tasks across a fleet of machines, making it invaluable for system administrators, DevOps engineers, and anyone managing a cluster of servers. It typically works by iterating through a list of hosts, establishing parallel SSH connections, and executing the specified command on each. The output from all hosts is usually collected and presented to the user, though the formatting can vary depending on the specific mssh implementation. Its primary benefits include automation, efficiency, and reducing manual repetitive tasks, especially useful for deployments, patching, configuration management, or health checks.

The command mssh is not a universally standardized Linux utility. Its implementation and available options can vary significantly. Many users create simple shell scripts or wrappers, while more robust versions might be community-driven projects. Therefore, the specific syntax and features described might differ from a particular mssh script or tool you encounter. Always check the specific documentation or source code if you're using an unfamiliar mssh implementation. Security considerations, such as proper SSH key management and host verification, are crucial when using any multi-host execution tool.

mssh is commonly used for:
System Health Checks: Quickly checking disk space, uptime, or running processes across a server farm.
Software Deployment: Distributing and installing packages or applications to multiple servers simultaneously.
Configuration Management: Pushing small configuration changes or restarting services on groups of machines.
Patching: Applying security patches or updates across a cluster.
Data Collection: Gathering log files or system metrics from various hosts.

Different mssh implementations handle output differently. Some might interleave output from various hosts, while others might prefix each line with the hostname or group output per host. For extensive output or structured data, piping mssh's output to tools like grep, awk, or custom scripts is often necessary to parse and analyze the results effectively.

The concept behind mssh emerged from the fundamental need for system administrators to manage multiple servers efficiently. As server infrastructures grew, manually logging into each machine became impractical. Early solutions often involved simple shell loops around the ssh command. Over time, these basic scripts evolved into more sophisticated tools and specialized projects (like pdsh or parallel-ssh) that provide advanced features like parallel execution, robust error handling, and output formatting. While there isn't a single definitive historical lineage for a command specifically named mssh, it represents this ongoing development towards automating multi-host interactions, driven by the increasing scale and complexity of distributed systems.

ssh(1), pdsh(1), cssh(1), pssh(1), ansible(1)