> For the complete documentation index, see [llms.txt](https://atomoh.gitbook.io/kubernetes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://atomoh.gitbook.io/kubernetes/en/lab-guides/labs/01-linux-basics-lab.md).
# Linux Basics Lab
> **Difficulty**: Beginner **Estimated Time**: 45 minutes **Last Updated**: February 11, 2026
## Learning Objectives
* Practice Linux process management commands
* Directly observe the isolation effect of Linux namespaces
* Understand resource limits through cgroups
* Practice file permissions and ownership management
## Prerequisites
* [ ] Linux terminal access (Ubuntu 20.04+ recommended)
* [ ] sudo privileges
* [ ] Completed [Linux Basics](/kubernetes/en/basic/01-linux-basics.md) learning
***
## Exercise 1: Process Management
### Goal
Practice process listing, background execution, and signal sending.
### Steps
**Step 1.1: Check currently running processes**
```bash
# Processes in the current terminal
ps aux | head -20
# View process relationships in tree format
ps auxf | head -30
```
**Step 1.2: Run a background process**
```bash
# Run a sleep process in the background
sleep 300 &
echo "PID: $!"
# Check background jobs
jobs -l
```
**Step 1.3: Send a signal to a process**
```bash
# Get the process ID
SLEEP_PID=$(pgrep -f "sleep 300")
echo "Sleep PID: $SLEEP_PID"
# Request termination with SIGTERM
kill $SLEEP_PID
# Verify the process has terminated
ps aux | grep "sleep 300" | grep -v grep
```
Need a hint?
* Use `kill -l` to see a list of available signals
* `kill -9 PID` forcefully terminates with SIGKILL
* `pkill -f "pattern"` allows name-based termination
### Verification
```bash
# The sleep process should not exist
pgrep -f "sleep 300" && echo "Still running" || echo "Termination complete"
```
***
## Exercise 2: Linux Namespace Isolation
### Goal
Create namespaces to observe process and network isolation.
### Steps
**Step 2.1: Verify PID namespace isolation**
```bash
# Run bash in a new PID namespace
sudo unshare --pid --fork --mount-proc bash -c '
echo "PID list inside the new namespace:"
ps aux
echo "Current process PID: $$"
'
```
Expected output:
```
PID list inside the new namespace:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.0 ... ... ... S ... 0:00 bash -c ...
root 2 0.0 0.0 ... ... ... R ... 0:00 ps aux
Current process PID: 1
```
**Step 2.2: Network namespace isolation**
```bash
# Create a network namespace
sudo ip netns add test-ns
# List namespaces
sudo ip netns list
# Check network inside the isolated namespace
sudo ip netns exec test-ns ip addr
# Cleanup
sudo ip netns delete test-ns
```
Need a hint?
* Host network interfaces are not visible inside the network namespace
* Only the `lo` (loopback) interface exists, and it's DOWN by default
* This is the principle behind container network isolation
### Verification
```bash
# Verify the namespace has been deleted
sudo ip netns list | grep test-ns && echo "Still exists" || echo "Deletion complete"
```
***
## Exercise 3: cgroup Resource Limits
### Goal
Use cgroups to limit process memory usage.
### Steps
**Step 3.1: Check cgroup information**
```bash
# Check cgroup v2 mount
mount | grep cgroup
# Check cgroup of current process
cat /proc/self/cgroup
# Check cgroup controllers
cat /sys/fs/cgroup/cgroup.controllers 2>/dev/null || echo "Using cgroup v1"
```
**Step 3.2: Check memory usage**
```bash
# System memory information
free -h
# Memory usage of specific processes
ps aux --sort=-%mem | head -10
```
**Step 3.3: Connection to Kubernetes resource limits**
```bash
# This is how resources.limits works in K8s
# Let's look at a Pod manifest example
cat << 'EOF'
apiVersion: v1
kind: Pod
metadata:
name: memory-demo
spec:
containers:
- name: memory-demo
image: nginx
resources:
requests:
memory: "64Mi"
limits:
memory: "128Mi"
EOF
```
Need a hint?
* K8s `resources.limits.memory` is translated to cgroup memory limits for the container
* Exceeding the limit results in OOMKilled status
* You can check resource limits with `kubectl describe pod`
***
## Exercise 4: File Permission Management
### Goal
Practice managing file permissions and ownership.
### Steps
**Step 4.1: Create a file and check permissions**
```bash
# Create a test file
mkdir -p /tmp/linux-lab
echo "Hello Linux" > /tmp/linux-lab/test.txt
# Check current permissions
ls -la /tmp/linux-lab/test.txt
```
**Step 4.2: Change permissions**
```bash
# Add execute permission
chmod +x /tmp/linux-lab/test.txt
ls -la /tmp/linux-lab/test.txt
# Set with numeric mode (read/write - read - none)
chmod 640 /tmp/linux-lab/test.txt
ls -la /tmp/linux-lab/test.txt
# Set the same permissions as K8s Secret volume defaults
chmod 0644 /tmp/linux-lab/test.txt
```
**Step 4.3: Change ownership**
```bash
# Check current user and group
id
# Change group (if executable)
sudo chown $USER:root /tmp/linux-lab/test.txt
ls -la /tmp/linux-lab/test.txt
```
### Verification
```bash
# Verify permissions are -rw-r--r--
stat -c "%a %U %G" /tmp/linux-lab/test.txt
```
***
## Cleanup
```bash
# Delete test files
rm -rf /tmp/linux-lab
# Clean up remaining processes
pkill -f "sleep 300" 2>/dev/null
```
## Troubleshooting
The unshare command is not found
Install the `util-linux` package:
```bash
sudo apt-get install util-linux # Ubuntu/Debian
sudo yum install util-linux # CentOS/RHEL
```
The ip netns command does not work
The `iproute2` package is required:
```bash
sudo apt-get install iproute2 # Ubuntu/Debian
sudo yum install iproute # CentOS/RHEL
```
## Next Steps
* [Linux Basics Quiz](/kubernetes/en/quiz-collection/quizzes/01-linux-basics-quiz.md)
* [Linux Advanced Skills Lab](/kubernetes/en/lab-guides/labs/02-linux-advanced-lab.md)