Redhat: Module Management

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2023 05 28 04 13 56


Modules are a new concept introduced in RHEL 8, and the yum/dnf command
has also been modified to handle them. The command can be used to
perform a number of operations on modules by specifying the module
subcommand with it. The following subsections elaborate with examples on
using this tool to list, enable, install, query, remove, and disable modules.
Listing Available and Installed Modules
The dnf command can list the modules available for installation from either or
both repos, as well as the modules that are already installed on the system.
To list all modules along with their stream, profile, and summary information
available from all configured repos:
You may limit the output to a list of modules available from a specific repo
such as AppStream by adding --repo AppStream to the above. The letters d, e, x, and i under the Stream and Profiles columns and at the last line of the
output indicate their status as default (d), enabled (e), disabled (x), or installed
(i).
To list all the streams for a specific module such as perl and display their
status:
The above output reveals that there are two streams (5.24 and 5.26) available
for the perl module from the AppStream repo, and the current default and
enabled version is the latter of the two.
To modify the above and list only the specified stream (5.24) for the module
perl:
To list all enabled module streams:
Similarly, you can use the --installed and --disabled options with dnf module
list to output only the installed or the disabled streams.
Refer to the module list subsection of the dnf command manual pages for
more details.
Installing and Updating Modules
Installing a module creates the necessary directory tree for all the packages
included in the module and all dependent packages, installs the required files
for the selected profile, and runs any post-installation steps. If the module
being loaded or a part of it is already present, the command attempts to
update all the packages included in the profile to the latest available versions.
By default, dnf prompts for a yes or no confirmation unless the -y flag is
entered with the command.
To install the perl module using its default stream and default profile:
The default stream and the default profile are the same, which is 5.26, and the
above command installed it.
To update a module called squid to the latest version:
To install the profile “common” with stream “rhel8” for the container-tools
module (run dnf module list to view available container-tools modules):
The syntax of entering module, stream, and profile together
(module:stream/profile) is illustrated on the above command line.
Displaying Module Information
Exhibiting information about a module shows its name, stream, version, list of
profiles, default profile, repo name it was installed or is available from,
summary, description, and artifacts. This information can be viewed by
supplying module info with dnf. Let’s take a look at the following examples.
To list all profiles available for the module perl: To limit the output to a particular stream such as 5.26:
To display details for a specific module stream (a non-default stream), specify
the module stream with the module name:
Refer to the module info subsection of the dnf command manual pages for
more details.
Removing Modules
Removing a module will uninstall all the included packages and delete all
associated files and directory structure. It also erases any dependencies as
part of the deletion process. By default, dnf prompts for a yes or no
confirmation unless the -y flag is specified at the command line.
To remove the container-tools module with “rhel8” stream:
The above output resolved dependencies and showed a list of the packages
that it would remove. It displayed the amount of disk space that their removal
would free up. After confirmation to proceed, it erased the identified packages
and verified their removal. A list of the removed packages was exposed at the
bottom of the output.