How to use the command 'genie' (with examples)

Genie is a command-line utility designed to facilitate a seamless experience of running systemd under the Windows Subsystem for Linux (WSL). Systemd is a popular system and service manager for Linux, and some applications that rely on it may not work properly in WSL environments without a helper like Genie. By setting up a “bottle” namespace, Genie emulates a more complete Linux environment, allowing systemd and systemd-managed services to run effectively.

Use case 1: Initialize the bottle (run once, at start)

Code:

genie -i

Motivation: Initializing the bottle is an essential first step for anyone wishing to use systemd in WSL. When starting a WSL session, the default setting doesn’t include systemd, making it challenging for users who rely on services that require systemd for their startup and operation. Initializing the bottle ensures that a pseudo-Linux environment suitable for systemd-based services is prepared, making it possible to tackle more complex tasks that mimic a standard Linux distribution setup.

Explanation:

• genie: This invokes the Genie command-line utility.
• -i: This flag is an argument to the Genie command that tells it to “initialize” or set up the bottle. This process involves starting the systemd system and preparing the environment needed to run it.

Example output:

Starting the bottle.
Bottle initialized successfully in the current WSL instance.

Use case 2: Run a login shell inside the bottle

Code:

genie -s

Motivation: After initializing the bottle, users will often want to start a shell session that fully benefits from the systemd environment. Running a login shell inside the bottle allows users to interact with WSL in a way that directly mirrors a standard Linux shell with systemd active. This can be particularly useful for developers who are testing deployment scripts or services that need systemd, enabling a more realistic test environment.

Explanation:

• genie: Again, this is the command-line utility being invoked.
• -s: This flag specifies that Genie should start a new interactive login shell within the already initialized bottle. This environment will include all necessary systemd functionalities.

Example output:

Welcome to Ubuntu 20.04.1 LTS (GNU/Linux 4.4.0-190-generic x86_64)
Systemd has been successfully started and is now running.

Use case 3: Run a specified command inside the bottle

Code:

genie -c command

Motivation: Sometimes, running a full shell isn’t necessary when you need to execute a specific command. Executing a command inside the bottle ensures that it benefits from the systemd environment and any other systemd-dependent services. This is particularly useful for scripting or automation, where specific tasks need to be carried out programmatically without starting an interactive shell.

Explanation:

• genie: The tool being used to manage systemd under WSL.
• -c: This flag tells Genie to run a specified command inside the bottle.
• command: This placeholder should be replaced by the actual command you wish to execute. By being run inside the bottle, the command benefits from any systemd-managed services and dependencies.

Example Output: Imagine the command was genie -c systemctl status sshd:

* ssh.service - OpenSSH Daemon
     Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2023-09-12 14:00:00 UTC; 2h 15min ago
     ...

Conclusion:

Genie serves as a versatile tool to bridge the gap between Linux’s systemd operational needs and the typical WSL environment, which lacks native support for systemd. Whether you’re initializing the bottle to kick-start your session, running a shell to perform multiple tasks, or executing a single command within the systemd-enabled namespace, Genie ensures you’re prepared for a more genuine Linux experience under Windows. By leveraging Genie, users can maintain consistency in their workflows, facilitate application testing, and leverage systemd’s capabilities seamlessly within WSL.