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Author image Ferenc Erki
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Rex - the friendly automation framework


Rex is an automation framework that is friendly to any combinations of local and remote execution, push and pull style of management, or imperative and declarative approach.

Its flexibility makes it a great fit for many different use cases, but most commonly Rex is used to automate application deployment and data center infrastructure management tasks.


    bash# rex -h                      # Show usage
    bash# rex -T                      # List tasks
    bash# rex uname                   # Run the 'uname' task
    bash# rex -H server[01..10] uname # Run the 'uname' task on all the specified hosts
    bash# rex -G production uname     # Run 'uname' on hosts on the 'production' hostgroup
    bash# rex deploy --gracefully     # Pass '--gracefully' to the 'deploy' task


    rex [<options>] [-H <host>] [-G <group>] <task> [<task-options>]
    rex -T[m|y|v] [<string>]

    -b     Run batch
    -e     Run the given code fragment
    -E     Execute a task on the given environment
    -G|-g  Execute a task on the given server groups
    -H     Execute a task on the given hosts (space delimited)
    -z     Execute a task on hosts from this command's output
    -K     Public key file for the ssh connection
    -P     Private key file for the ssh connection
    -p     Password for the ssh connection
    -u     Username for the ssh connection
    -d     Show debug output
    -ddd   Show more debug output (includes profiling output)
    -m     Monochrome output: no colors
    -o     Output format
    -q     Quiet mode: no log output
    -qw    Quiet mode: only output warnings and errors
    -Q     Really quiet: output nothing
    -T     List tasks
    -Ta    List all tasks, including hidden
    -Tm    List tasks in machine-readable format
    -Tv    List tasks verbosely
    -Ty    List tasks in YAML format
    -c     Turn cache ON
    -C     Turn cache OFF
    -f     Use this file instead of Rexfile
    -F     Force: disregard lock file
    -h     Display this help message
    -M     Load this module instead of Rexfile
    -O     Pass additional options, like CMDB path
    -s     Use sudo for every command
    -S     Password for sudo
    -t     Number of threads to use (aka 'parallelism' param)
    -v     Display (R)?ex version


When you run rex it reads the file Rexfile in the current working directory. A Rexfile consists of 2 major parts: Configuration and Task Definitions.


Simple Authentication

    user "bruce";
    password "batman";

Key Authentication

    private_key "/path/to/your/private/key.file";
    public_key "/path/to/your/public/key.file";

Define Logging

    logging to_file => "rex.log";
    logging to_syslog => "local0";

Group your servers

Rex gives you the ability to define groups of servers. Groups can be defined the Rexfile:

    group "frontends" => "frontend01", "frontend02", "frontend03", "frontend04", "frontend[05..09]";

Groups can also be defined in a server.ini file:


Other Configuration

    timeout 10;    # ssh timeout
    parallelism 2; # execute tasks in parallel

Defining tasks

A basic task looks like this:

    # task description
    desc "This task tells you how long since the server was rebooted";
    # task definition
    task "shortname", sub {
        say run "uptime";

You can also set a default server group:

    desc "This is a long description of a task";
    task "shortname", group => "frontends", sub {
        say run "uptime";


Tab completion scripts are provided for Bash and Zsh in the share directory. They provide completions for the available CLI options, hosts, groups, environments and tasks.