Updating a Low-memory Server Running Fedora 36+

The Problem: dnf requires a lot of RAM!

I have been running Fedora Server for several years on a server with a small amount of RAM (1 GiB) and a small amount of swap (1.2 GiB). Over the last several months, I ran into a situation where the server was having high loads on occasion. Thinking that something malicious was happening, I investigated.

As it turned out, what was happening is that I had auto updates for Fedora turned on and they were failing due to the amount of metadata dnf had to handle—​it was running out of RAM and swap to complete the update process. This seemed crazy since I have successfully being using Fedora on that machine for some time and have upgraded the distribution in place many times.

In researching the situation, several people have run across this particular issue. In fact, there is a Red Hat Bugzilla issue for the situation. Buried deep in the posts, I ran across several things that were very helpful. First, as a background, it appears that the implementation of dnf (the standard Fedora package manager for years) has been written in Python (to some degree). As a result of using Python and the large number of packages in the Fedora repositories, just processing the updates and their dependencies can take a lot of RAM.

The Solution: microdnf

In the bug tracker post, though, there was several suggested solutions. The most promising was the use of microdnf in place of dnf for handling package management. microdnf is written in C and requires much less RAM and other resources to run. In fact, it was designed to run as the package manager for containers, so it is designed to reduce the resources required for package management.

Given that dnf was having issues, it might be challenging to install microdnf in the first place. The suggestion was to run the following to reduce the memory footprint for installing microdnf:

dnf --repoid=fedora makecache && dnf --repoid=fedora install microdnf

In particular, this is restricting the effort and memory costs to make the repository cache and installing microdnf by limiting dnf to using the fedora repository. Once it is installed you can run microdnf, much like you can dnf.

One operation that I wasn’t sure about, though, was how to update to a newer version of Fedora. For example, from Fedora 36 to Fedora 38. Thankfully, the Red Hat Bugzilla issue provided an example of how to do that:

microdnf --releasever=38 distro-sync

microdnf Command Reference

Here is the help provided by microdnf on the command line:

$ microdnf -h
Usage:
  dnf5 <COMMAND> [--help] ...

Description:
  DNF5 is a program for maintaining packages.

Software Management Commands:
  install                                Install software
  upgrade                                Upgrade software
  remove                                 Remove (uninstall) software
  distro-sync                            Upgrade or downgrade installed software to the latest available versions
  downgrade                              Downgrade software
  reinstall                              Reinstall software
  swap                                   Remove software and install another in one transaction
  mark                                   Change the reason of an installed package
  autoremove                             Remove all unneeded packages originally installed as dependencies.
  check-upgrade                          Check for available package upgrades

Query Commands:
  leaves                                 List groups of installed packages not required by other installed packages
  repoquery                              Search for packages matching various criteria
  search                                 Search for software matching all specified strings
  list                                   Lists packages depending on the packages' relation to the system
  info                                   Lists packages depending on the packages' relation to the system

Subcommands:
  group                                  Manage comps groups
  environment                            Manage comps environments
  module                                 Manage modules
  history                                Manage transaction history
  repo                                   Manage repositories
  advisory                               Manage advisories

Compatibility Aliases:
  dg                                     Alias for 'downgrade'
  groupinfo                              Alias for 'group info'
  grouplist                              Alias for 'group list'
  in                                     Alias for 'install'
  ls                                     Alias for 'list'
  rei                                    Alias for 'reinstall'
  repoinfo                               Alias for 'repo info'
  repolist                               Alias for 'repo list'
  rm                                     Alias for 'remove'
  up                                     Alias for 'upgrade'
  update                                 Alias for 'upgrade'
  updateinfo                             Alias for 'advisory'
  upgrade-minimal                        Alias for 'upgrade --minimal'
  check-update                           Alias for 'check-upgrade'

Commands:
  clean                                  Remove or expire cached data
  download                               Download software to the current directory
  makecache                              Generate the metadata cache

Global options:
  -h, --help                             Print help
  --config=CONFIG_FILE_PATH              Configuration file location
  -q, --quiet                            In combination with a non-interactive command, shows just the relevant cont
                                         ent. Suppresses messages notifying about the current state or actions of dn
                                         f5.
  --setopt=[REPO_ID.]OPTION=VALUE        set arbitrary config and repo options
  --setvar=VAR_NAME=VALUE                set arbitrary variable
  -y, --assumeyes                        automatically answer yes for all questions
  --assumeno                             automatically answer no for all questions
  --best                                 try the best available package versions in transactions
  --no-best                              do not limit the transaction to the best candidate
  --no-docs                              Don't install files that are marked as documentation (which includes man pa
                                         ges and texinfo documents)
  -x package,..., --exclude=package,...  exclude packages by name or glob
  --enable-repo=REPO_ID,...              Enable additional repositories. List option. Supports globs, can be specifi
                                         ed multiple times.
  --disable-repo=REPO_ID,...             Disable repositories. List option. Supports globs, can be specified multipl
                                         e times.
  --repo=REPO_ID,...                     Enable just specific repositories. List option. Supports globs, can be spec
                                         ified multiple times.
  --no-gpgchecks                         disable gpg signature checking (if RPM policy allows)
  --no-plugins                           disable all plugins
  --enable-plugin=PLUGIN_NAME,...        Enable plugins by name. List option. Supports globs, can be specified multi
                                         ple times.
  --disable-plugin=PLUGIN_NAME,...       Disable plugins by name. List option. Supports globs, can be specified mult
                                         iple times.
  --comment=COMMENT                      add a comment to transaction
  --installroot=ABSOLUTE_PATH            set install root
  --use-host-config                      use configuration, reposdir, and vars from the host system rather than the
                                         installroot
  --releasever=RELEASEVER                override the value of $releasever in config and repo files
  --debugsolver                          Dump detailed solving results into files
  --version                              Show DNF5 version and exit

Options Compatibility aliases:
  --nobest                               Alias for '--no-best'
  --nodocs                               Alias for '--no-docs'
  --enablerepo=REPO_ID,...               Alias for '--enable-repo'
  --disablerepo=REPO_ID,...              Alias for '--disable-repo'
  --repoid=REPO_ID,...                   Alias for '--repo'
  --nogpgcheck                           Alias for '--no-gpgchecks'
  --noplugins                            Alias for '--no-plugins'
  --enableplugin=PLUGIN_NAME,...         Alias for '--enable-plugin'
  --disableplugin=PLUGIN_NAME,...        Alias for '--disable-plugin'

It is interesting that microdnf is actually called dnf5. The documentation for dnf5 provides some nice additional information . dnf5 is a rewrite of dnf in C++ and is planned to replace dnf in Fedora 41, a few releases in the future.

In any case, using microdnf made it possible for me to continue to use Fedora on my small server where dnf ran out of RAM resources to run.