Introduction to the systemd-cgls Command

The systemd-cgls command is a Linux utility used to list and query control groups (cgroups) on a system. It is part of the systemd suite of tools and is used to manage and monitor system processes. The command can be used to view cgroup information and the processes associated with them.

Basic Usage and Syntax

The basic syntax for the systemd-cgls command is:

systemd-cgls [OPTIONS] [CGROUP...]

The command takes a number of different options and flags, which can be used to customize the output and query specific cgroups. Some of the most commonly used options are listed below:

• -h, --help - displays a help message.
• -t, --tree - displays a tree-like output.
• -r, --recursive - recursively lists all cgroups in the hierarchy.
• -l, --list - lists all cgroups in the hierarchy.
• -d, --depth - displays the depth of the cgroups.
• -n, --no-pager - disables the pager.

Examples of Common Use Cases

The systemd-cgls command can be used to view and query information about cgroups on a system. Some common examples of how to use the command are listed below:

• To view the cgroups hierarchy on a system:

  systemd-cgls

• To view the cgroups hierarchy in a tree-like output:

  systemd-cgls -t

• To view the cgroups hierarchy recursively:

  systemd-cgls -r

• To view the cgroups hierarchy with the depth of each cgroup:

  systemd-cgls -d

• To list all cgroups in the hierarchy:

  systemd-cgls -l

Advanced Options and Flags

The systemd-cgls command has a number of advanced options and flags that can be used to customize the output and query specific cgroups. Some of the most commonly used advanced options and flags are listed below:

• -p, --processes - displays the processes associated with each cgroup.
• -s, --all-slices - displays all slices, including those with no cgroups.
• -a, --all - displays all cgroups, including those with no processes.
• -e, --extra - displays extra information about each cgroup.
• -f, --full - displays full information about each cgroup.
• -x, --full-tree - displays a full tree-like output.

Examples in Real-World Scenarios

The systemd-cgls command can be used in a variety of real-world scenarios. Some examples of how the command can be used are listed below:

• To view the processes associated with a specific cgroup:

  systemd-cgls -p /sys/fs/cgroup/systemd/user.slice/user-1001.slice

• To view the cgroups hierarchy with extra information:

  systemd-cgls -e

• To view the cgroups hierarchy in a full tree-like output:

  systemd-cgls -x

• To view all cgroups in the hierarchy, including those with no processes:

  systemd-cgls -a

Troubleshooting Tips and Potential Errors

When using the systemd-cgls command, there are a few potential errors that can occur. Some troubleshooting tips and potential errors are listed below:

• If the command is not found, make sure that the systemd-cgls binary is installed on the system.
• If the command does not produce any output, make sure that the cgroup hierarchy is properly configured.
• If the command produces an error, make sure that the correct options and flags are being used.
• If the command produces an error, make sure that the user has the proper permissions to query the cgroups.