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Linux Basics Lab Guide ​

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 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 ​