diff --git a/knowledge base/cloud computing/aws/ssm.md b/knowledge base/cloud computing/aws/ssm.md
index fec4056..b8f66ff 100644
--- a/knowledge base/cloud computing/aws/ssm.md	
+++ b/knowledge base/cloud computing/aws/ssm.md	
@@ -40,6 +40,10 @@ aws ssm start-session \
   --target 'instance-id' \
   --document-name 'CustomCommandSessionDocument' \
   --parameters '{"logpath":["/var/log/amazon/ssm/amazon-ssm-agent.log"]}'
+aws ssm send-command \
+  --instance-ids 'i-0123456789abcdef0' \
+  --document-name 'AWS-RunShellScript' \
+  --parameters commands="echo 'hallo!'"
 ```
 
 </details>
@@ -52,6 +56,9 @@ instance_id='i-08fc83ad07487d72f' \
 && eval $(aws ssm get-connection-status --target "$instance_id" --query "Status=='connected'" --output text) \
 && aws ssm start-session --target "$instance_id" \
 || (echo "instance ${instance_id} not available" >&2 && false)
+
+aws ssm send-command --instance-ids "i-08fc83ad07487d72f" \
+  --document-name "AWS-RunShellScript" --parameters commands="echo 'hallo!'"
 ```
 
 </details>
diff --git a/knowledge base/gitlab.md b/knowledge base/gitlab.md
index f2f0ff1..643eef6 100644
--- a/knowledge base/gitlab.md	
+++ b/knowledge base/gitlab.md	
@@ -22,18 +22,33 @@
 
 ## Omnibus
 
+<details>
+  <summary>Installation</summary>
+
+Refer [Install self-managed GitLab].
+
+</details>
 <details>
   <summary>Configuration</summary>
 
+[Template][omnibus configuration template]
+
 The application of configuration changes is handled by [Chef Infra].<br/>
 It runs checks, ensures directories, permissions, and services are in place and working, and restarts components if any
 of their configuration files have changed.
 
 ```sh
-# Edit and validate.
+# Validate.
+# Just makes sure the file is readable from a ruby app.
+# Gitlab's internal checks do not really do anything.
 sudo vim '/etc/gitlab/gitlab.rb'
 sudo ruby -c '/etc/gitlab/gitlab.rb'
+sudo gitlab-ctl show-config
+
+# Check if there are any configuration in the configuration file that is removed in specified versions.
+# Useless by experience.
 sudo gitlab-ctl check-config
+sudo gitlab-ctl check-config -v '16.11.0'
 
 # Make Gitlab aware of the changes.
 sudo gitlab-ctl reconfigure
@@ -556,6 +571,8 @@ Solution: give that user _developer_ access or have somebody else with enough pr
 - [Tutorial: Use Buildah in a rootless container with GitLab Runner Operator on OpenShift]
 - [Use kaniko to build Docker images]
 - [Specify when jobs run with `rules`][specify when jobs run with rules]
+- [Install self-managed GitLab]
+- [Omnibus configuration template]
 
 <!--
   References
@@ -586,8 +603,10 @@ Solution: give that user _developer_ access or have somebody else with enough pr
 [docker machine's supported cloud providers]: https://docs.gitlab.com/runner/configuration/autoscale.html#supported-cloud-providers
 [global settings]: https://docs.gitlab.com/charts/charts/globals.html
 [how to restart gitlab]: https://docs.gitlab.com/ee/administration/restart_gitlab.html
+[install self-managed gitlab]: https://about.gitlab.com/install
 [merge request approval rules]: https://gitlab.ops.apolloagriculture.com/help/user/project/merge_requests/approvals/rules
 [minimal minikube example values file]: https://gitlab.com/gitlab-org/charts/gitlab/-/blob/master/examples/values-minikube-minimum.yaml
+[omnibus configuration template]: https://gitlab.com/gitlab-org/omnibus-gitlab/-/raw/master/files/gitlab-config-template/gitlab.rb.template
 [operator code]: https://gitlab.com/gitlab-org/cloud-native/gitlab-operator
 [operator guide]: https://docs.gitlab.com/operator/
 [predefined ci/cd variables reference]: https://docs.gitlab.com/ee/ci/variables/predefined_variables.html
diff --git a/snippets/gitlab.omnibus.install.sh b/snippets/gitlab.omnibus.install.sh
index 31481a0..9f20dcd 100644
--- a/snippets/gitlab.omnibus.install.sh
+++ b/snippets/gitlab.omnibus.install.sh
@@ -38,10 +38,4 @@ sudo EXTERNAL_URL="http://ip-172-31-73-256.eu-south-2.compute.internal" dnf inst
 # File automatically removed after 24h.
 sudo cat '/etc/gitlab/initial_root_password'
 
-# Should one need to tune the configuration.
-sudo dnf -y install 'vim'
-sudo vim '/etc/gitlab/gitlab.rb'
-sudo gitlab-ctl check-config
-sudo gitlab-ctl reconfigure
-
 xdg-open 'http://ip-172-31-73-256.eu-south-2.compute.internal'
diff --git a/snippets/gitlab.omnibus.reconfigure.sh b/snippets/gitlab.omnibus.reconfigure.sh
index 51f7988..51f01e6 100644
--- a/snippets/gitlab.omnibus.reconfigure.sh
+++ b/snippets/gitlab.omnibus.reconfigure.sh
@@ -1,6 +1,12 @@
 #!sh
 
+# Updated config template available at
+# https://gitlab.com/gitlab-org/omnibus-gitlab/blame/master/files/gitlab-config-template/gitlab.rb.template
+
+# Local template (corresponding to the installed version) available at '/opt/gitlab/etc/gitlab.rb.template'
+
+sudo dnf -y install 'ruby' 'vim'
 sudo vim '/etc/gitlab/gitlab.rb'
-sudo gitlab-ctl check-config
-sudo gitlab-ctl diff-config   # if one really needs to
+sudo ruby -c '/etc/gitlab/gitlab.rb'
+sudo gitlab-ctl show-config
 sudo gitlab-ctl reconfigure