diff --git a/.vscode/settings.json b/.vscode/settings.json
index 56b9931..0a4a5e1 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -308,6 +308,7 @@
         "wodle",
         "xattr",
         "xkcd",
+        "yellowdog",
         "yubikey",
         "zstd"
     ]
diff --git a/README.md b/README.md
index 13b5cef..15788b4 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,6 @@ This commonly applies to telecommunication, computer networks, and computer hard
 
 In short, my private collection of notes and scripts. I use them to ease my tech life.
 
-## Table of contents <!-- omit in toc -->
-
 1. [License](#license)
 1. [Status](#status)
 1. [Support](#support)
@@ -37,7 +35,8 @@ I might accept suggestions, though. Use the repository's hosting platform's tool
 - [myshittycode.com]
 
 <!--
-  References
+  Reference
+  ═╬═Time══
   -->
 
 <!-- In-article sections -->
diff --git a/knowledge base/dnf.md b/knowledge base/dnf.md
index cf42115..5ff8b60 100644
--- a/knowledge base/dnf.md	
+++ b/knowledge base/dnf.md	
@@ -1,5 +1,9 @@
 # DNF
 
+A.K.A. _Dandified YUM_.
+
+Rewrite of [YUM] using [`libsolv`][libsolv].
+
 1. [TL;DR](#tldr)
 1. [Lock packages versions](#lock-packages-versions)
 1. [Further readings](#further-readings)
@@ -166,10 +170,13 @@ Not to mention,
 - [How to lock kernel (or another package) on Fedora]
 
 <!--
-  References
+  Reference
+  ═╬═Time══
   -->
 
-<!-- In-article sections -->
+<!-- Knowledge base -->
+[yum]: yum.md
+
 <!-- Upstream -->
 [dnf command reference]: https://dnf.readthedocs.io/en/latest/command_ref.html
 [dnf configuration reference]: https://dnf.readthedocs.io/en/latest/conf_ref.html
@@ -180,4 +187,5 @@ Not to mention,
 [how to install only security and bugfixes updates with dnf]: https://fedoramagazine.org/how-to-install-only-security-and-bugfixes-updates-with-dnf/
 [how to lock kernel (or another package) on fedora]: https://robbinespu.gitlab.io/posts/locking-package-fedora/
 [how to use yum/dnf to downgrade or rollback some package updates?]: https://access.redhat.com/solutions/29617
+[libsolv]: https://github.com/openSUSE/libsolv
 [man page]: https://man7.org/linux/man-pages/man8/dnf.8.html
diff --git a/knowledge base/yum.md b/knowledge base/yum.md
new file mode 100644
index 0000000..0d78edf
--- /dev/null
+++ b/knowledge base/yum.md	
@@ -0,0 +1,64 @@
+# Yellowdog Updater Modified
+
+Command-line utility for RPM used by Red Hat Linux and derivates.<br/>
+Replaced by [DNF] in Fedora.
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+   1. [Sources](#sources)
+
+## TL;DR
+
+Global configuration file at `/etc/yum/yum.conf`.<br/>
+Repositories `.repo` files reside under `/etc/yum.repos.d/`.<br/>
+Configuration files use the INI format. **Some** options in the repository definition override the global settings for
+YUM.
+
+<details>
+  <summary>Usage</summary>
+
+```sh
+# Check for updates.
+sudo yum check-update
+
+# List available packages.
+sudo yum --showduplicates list available 'gitlab-ee'
+
+# Display information about packages.
+sudo yum info 'gitlab-ee'
+
+# Install packages.
+sudo yum install 'buildah' 'jq-0.5.6-1.fc24'
+sudo yum -y install 'Downloads/tito-0.6.2-1.fc22.noarch.rpm' --setopt='install_weak_deps=False'
+sudo yum install 'https://kojipkgs.fedoraproject.org/packages/tito/0.6.0/1.fc22/noarch/tito-0.6.0-1.fc22.noarch.rpm'
+
+# Upgrade packages.
+sudo yum update 'gitlab-ee-16.11.3'
+
+# Clear the cache.
+sudo yum clean packages
+sudo yum clean all
+```
+
+</details>
+
+## Further readings
+
+- [DNF]
+
+### Sources
+
+- [What is yum and how do I use it?]
+- [Yum Command Cheat Sheet for Red Hat Enterprise Linux]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- Knowledge base -->
+[dnf]: dnf.md
+
+<!-- Upstream -->
+[what is yum and how do i use it?]: https://access.redhat.com/solutions/9934
+[yum command cheat sheet for red hat enterprise linux]: https://access.redhat.com/articles/yum-cheat-sheet
diff --git a/snippets/gitlab.package.sh b/snippets/gitlab.package.sh
index db1d6f7..f1eccbf 100644
--- a/snippets/gitlab.package.sh
+++ b/snippets/gitlab.package.sh
@@ -86,13 +86,15 @@ gitlab-rails runner '
 sudo yum check-update
 sudo yum info 'gitlab-ee'        # informational
 sudo rpm -qa | grep 'gitlab-ee'  # informational
+sudo yum --showduplicates list available 'gitlab-ee'
 sudo gitlab-backup create        # not strictly necessary: the upgrade will create a partial one
 tmux new-session -A -s 'gitlab-upgrade' "sudo yum update 'gitlab-ee'"
+tmux new-session -A -s 'gitlab-upgrade' "sudo yum update 'gitlab-ee-16.11.3'"
 sudo gitlab-rake 'gitlab:check'
 
 # Password reset
 sudo gitlab-rake 'gitlab:password:reset[root]'
-sudo gitlab-rails console \
+sudo gitlab-rails console
 	# --> user = User.find_by_username 'root'
 	# --> user.password = 'QwerTy184'
 	# --> user.password_confirmation = 'QwerTy184'