Clarify kernel tuning limit documentation

.github/workflows/markdown-lint.yml

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+name: Markdown lint
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v4
+        with:
+          python-version: "3.11"
+      - name: Install pymarkdown
+        run: pip install pymarkdownlnt
+      - name: Run pymarkdown
+        run: pymarkdown --config .pymarkdown.json scan .

.pre-commit-config.yaml

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+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.5.0
+    hooks:
+      - id: end-of-file-fixer
+      - id: trailing-whitespace
+  - repo: https://github.com/jackdewinter/pymarkdown
+    rev: v0.9.14
+    hooks:
+      - id: pymarkdown
+        args: ["scan", "."]
+        additional_dependencies: []

.pymarkdown.json

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+{
+  "plugins": {
+    "md013": {
+      "enabled": false
+    },
+    "md033": {
+      "allowed_elements": [
+        "br"
+      ]
+    }
+  }
+}

Automation/Ansible-Beginner.md

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+# Learning Ansible
+
+- **Author:** nduytg
+- **Version:** 0.3
+- **Date:** 2017-04-12
+- **Tested on:** Ubuntu 16.04
+
+This quick-start shows how to install Ansible on Ubuntu and exercise it against
+lightweight LXC containers that simulate a small fleet of hosts.
+
+## Installation options
+
+### Option 1: Clone from Git
+
+```bash
+sudo apt-get install git-core
+cd ~
+git clone https://github.com/ansible/ansible
+cd ansible
+git log
+git submodule update --init --recursive
+sudo apt-get install python-jinja2 python-paramiko python-yaml sshpass
+```
+
+Activate Ansible's development environment and confirm the binary is available.
+
+```bash
+which ansible
+less ./hacking/env-setup
+source ./hacking/env-setup
+which ansible
+ansible --version
+```
+
+### Option 2: Install from apt
+
+```bash
+sudo apt-get update
+sudo apt-get install software-properties-common
+sudo apt-add-repository ppa:ansible/ansible
+sudo apt-get update
+sudo apt-get install ansible
+```
+
+## Prepare target containers with LXC
+
+Install LXC on the control node and create a few Ubuntu containers that mimic a
+small environment.
+
+```bash
+sudo apt-get update
+sudo apt-get install lxc
+lxc-ls --fancy
+```
+
+Create two web servers and one database server.
+
+```bash
+sudo lxc-create -n web1 -t ubuntu
+sudo lxc-create -n web2 -t ubuntu
+sudo lxc-create -n db1 -t ubuntu
+```
+
+List and start the containers as background services.
+
+```bash
+lxc-ls -f
+sudo lxc-start -n web1 -d
+sudo lxc-start -n web2 -d
+sudo lxc-start -n db1 -d
+```
+
+Log into a container to satisfy Ansible's prerequisites (Python 2.x and SSH).
+
+```bash
+sudo lxc-attach -n web1
+sudo apt-get install python-minimal
+exit
+```
+
+Repeat for the remaining containers as needed.
+
+## Create an inventory
+
+Build a simple inventory that groups the LXC instances into logical roles.
+
+```ini
+# inventory
+[allservers]
+10.0.3.113
+10.0.3.247
+10.0.3.95
+
+[web]
+10.0.3.247
+10.0.3.95
+
+[database]
+10.0.3.113
+```
+
+## Run ad-hoc commands
+
+Verify connectivity and perform common administrative actions.
+
+```bash
+ansible allservers -m ping -u ubuntu -i inventory
+ansible allservers -a "free -h" -u ubuntu -i inventory
+ansible allservers -a "apt list --installed | grep nginx" -u ubuntu -i inventory
+ansible allservers -a "apt-get update" -u root -i inventory
+ansible web -a "apt-get install -y nginx" -u root -i inventory
+ansible web -m service -a "name=nginx state=restarted" -u root -i inventory
+```

Backup/backup-rsync-crontab.md

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+# Rsync Backup Managed by Cron
+
+- **Author:** nduytg
+- **Version:** 0.5
+- **Date:** 2017-11-21
+- **Tested on:** CentOS 7
+
+Automate incremental backups with `rsync` and `cron`. Start with a local copy,
+expand to a remote target over SSH, and finish by restarting the cron service to
+apply schedule changes.
+
+## Local dry run
+
+```bash
+sudo yum install rsync
+rsync -av --dry-run --delete /home/nduytg/source/ /home/nduytg/backup/
+```
+
+## Remote dry run over SSH
+
+```bash
+sudo yum install openssh-clients rsync
+rsync -av --dry-run --delete -e ssh /home/nduytg/source/ \
+  root@192.168.31.131:/root/backup
+```
+
+Generate SSH keys and copy the public key to the remote host to avoid
+interactive password prompts when cron executes the job.
+
+## Schedule the synchronization
+
+```bash
+sudo crontab -e
+```
+
+Example entry (run every two minutes during testing):
+
+```cron
+*/2 * * * * rsync -av --delete -e ssh /home/nduytg/source/ \
+  root@192.168.31.131:/root/backup > /dev/null 2>&1
+```
+
+Restart the cron daemon after editing the schedule.
+
+```bash
+sudo systemctl restart crond
+```