Crucial_Linux_Commands_For_CloudAndDevOpsEngineer

As a Cloud and DevOps Engineer, mastering Linux commands is crucial for managing cloud infrastructure, automating deployments, and troubleshooting issues. Below is a categorized list of essential Linux commands:

1. System Monitoring & Performance

top / htop – Display system processes and resource usage.
vmstat – Show system performance statistics.
iostat – Monitor CPU and disk I/O performance.
free -m – Check available memory.
df -h – Check disk space usage.
du -sh * – Show disk usage of directories.
uptime – Display system uptime.
ps aux – View running processes.
kill -9 <PID> – Terminate a process forcefully.
netstat -tulnp / ss -tulnp – List open ports and services.

2. File Management & Permissions

ls -lah – List files with human-readable sizes and hidden files.
cp -r src dst – Copy directories recursively.
mv oldname newname – Rename/move files.
rm -rf dir/ – Remove files/directories recursively.
chmod 755 file – Modify file permissions.
chown user:group file – Change file ownership.
find /path -type f -name "*.log" – Find files by name.
locate filename – Find a file quickly.

3. User & Group Management

whoami – Display current user.
id – Show user ID (UID) and group ID (GID).
sudo su - – Switch to root user.
adduser username / userdel -r username – Add or remove a user.
passwd username – Change user password.
usermod -aG groupname username – Add user to a group.
groups username – List user's groups.

4. Networking & Connectivity

ip a / ifconfig – Show network interfaces.
ping google.com – Test network connectivity.
traceroute google.com – Trace network path to a host.
curl -I https://example.com – Fetch HTTP headers.
wget https://example.com/file.zip – Download files from a URL.
scp user@host:/path/file . – Secure copy files from a remote server.
rsync -avz src/ dest/ – Sync files between directories or servers.

5. Logs & Debugging

tail -f /var/log/syslog – View logs in real-time.
journalctl -xe – View system logs.
dmesg | grep error – Check kernel logs for errors.
cat /var/log/auth.log – Check authentication logs.
grep "error" /var/log/app.log – Search for "error" in logs.

6. Package Management

Debian/Ubuntu:
- apt update && apt upgrade -y – Update and upgrade packages.
- apt install package – Install a package.
- apt remove package – Remove a package.
RHEL/CentOS:
- yum update -y / dnf update -y
- yum install package / dnf install package
Common:
- dpkg -i package.deb – Install a .deb package.
- rpm -ivh package.rpm – Install an .rpm package.

7. Process & Job Management

& – Run a process in the background (e.g., command &).
jobs – List background jobs.
fg %1 – Bring job 1 to the foreground.
nohup command & – Run a command even after logout.
tmux / screen – Persistent terminal sessions.

8. Disk & Partition Management

fdisk -l – List disk partitions.
lsblk – Show block devices.
mount /dev/sdb1 /mnt – Mount a partition.
umount /mnt – Unmount a partition.
mkfs.ext4 /dev/sdb1 – Format a disk with ext4.

9. Compression & Archiving

tar -cvf archive.tar directory/ – Create a tar archive.
tar -xvf archive.tar – Extract a tar archive.
tar -czvf archive.tar.gz directory/ – Compress using gzip.
zip -r archive.zip directory/ – Zip a directory.
unzip archive.zip – Extract a zip file.

10. SSH & Remote Access

ssh user@host – Connect to a remote server.
ssh-keygen -t rsa -b 4096 – Generate an SSH key pair.
ssh-copy-id user@host – Copy SSH key to a server.
scp file user@host:/path/ – Securely copy files.

11. Cron Jobs & Automation

crontab -e – Edit cron jobs.
crontab -l – List cron jobs.
Example: 0 2 * * * /path/script.sh (Run script at 2 AM daily).

12. Kubernetes & Docker Commands

Docker:
- docker ps – List running containers.
- docker images – List available images.
- docker exec -it container_id bash – Access a running container.
- docker-compose up -d – Start services in the background.
Kubernetes:
- kubectl get pods – List running pods.
- kubectl logs pod-name – View logs of a pod.
- kubectl apply -f deployment.yaml – Deploy an application.

13. Cloud-Specific Commands

AWS CLI:
- aws s3 ls – List S3 buckets.
- aws ec2 describe-instances – Get EC2 instance details.
- aws rds describe-db-instances – Get RDS instance details.
- aws configure – Set up AWS CLI credentials.

These commands form the foundation of Linux system administration and are crucial for Cloud and DevOps engineers.

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