Week 1 – Linux + Networking Foundations (Cloud Base)
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🚀 Week 1 – Linux + Networking Foundations (Cloud Base)
🐧 Linux Section
✅ File System Commands
pwd # show current directory path
ls # list files
ls -l # long listing (permissions, owner, size)
ls -a # show hidden files
ls -lh # human readable sizes
ls -lrt # latest modified files at bottom
cd /var/log # move to log directory
cd .. # go back one directory
mkdir test # create directory
mkdir -p a/b/c # create nested directories
cp file1 file2 # copy file
cp -r dir1 dir2 # copy directory recursively
mv file newfile # rename file
mv file /tmp # move file
rm file # delete file
rm -r dir # delete directory
rm -rf dir # force delete (careful ⚠️)
find / -name nginx # search file by name
du -sh * # check size of each file/folder
tree # show directory structure
✅ Permissions & Ownership
ls -l # view permissions
chmod 755 file # rwxr-xr-x
chmod +x script.sh # add execute permission
chown user file # change owner
chown user:group file # change owner + group
chgrp dev file # change group only
umask # show default permission mask
Special bits
chmod 4755 file # SUID
chmod 2755 dir # SGID
chmod 1777 /shared # sticky bit (like /tmp)
✅ Process Management
ps # current shell processes
ps aux # all processes detailed
top # live CPU/memory monitor
htop # better UI monitor
kill 1234 # stop process using PID
kill -9 1234 # force kill
pkill nginx # kill by name
bg # run job in background
fg # bring job to foreground
jobs # list background jobs
nice -n 10 app # lower CPU priority
uptime # server running time + load
✅ Services (systemctl)
systemctl start nginx # start service
systemctl stop nginx # stop service
systemctl restart nginx # restart service
systemctl reload nginx # reload config only
systemctl status nginx # check service status
systemctl enable nginx # start at boot
systemctl disable nginx # disable at boot
journalctl -xe # view system logs
journalctl -u nginx # logs of specific service
✅ Logs (Debugging hero tools)
cd /var/log # go to logs directory
tail file.log # last 10 lines
tail -f file.log # live log streaming
less file.log # scroll log safely
grep ERROR file.log # search only ERROR lines
grep -i fail file.log # case-insensitive search
awk '{print $1}' file.log # print first column
cut -d" " -f1 file.log # split and extract column
✅ Disk & Storage
df -h # disk usage summary
du -sh * # folder size
du -ah | sort -rh # biggest files first
lsblk # show disks
mount # show mounted volumes
mount /dev/sdb1 /mnt # mount disk
umount /mnt # unmount disk
✅ Memory & System Info
free -m # memory usage
top # CPU/memory usage
vmstat # performance stats
cat /proc/meminfo # detailed memory info
✅ Package Manager
Ubuntu/Debian
apt update # refresh repo list
apt upgrade # upgrade packages
apt install nginx # install package
apt remove nginx # uninstall
apt search docker # search package
RHEL/CentOS
yum install nginx # install
yum remove nginx # remove
yum update # update packages
✅ Bash Scripting Basics
#!/bin/bash # shebang
name="ghouse" # variable
echo $name # print variable
if [ $name == "ghouse" ]; then # condition
echo "Hello"
fi
for i in {1..5}; do # loop
echo $i
done
Run:
chmod +x script.sh # make executable
./script.sh # run script
🌐 Networking Section
✅ IP & Interface
ip a # show IP address
ip route # show routes
ifconfig # old command alternative
hostname -I # show local IP
✅ DNS
nslookup google.com # check DNS resolution
dig google.com # detailed DNS info
cat /etc/resolv.conf # DNS server config
✅ Connectivity
ping google.com # test connectivity
traceroute google.com # show path packets take
mtr google.com # live traceroute (if installed)
✅ Ports & Services
netstat -tulnp # show open ports + process
ss -lntp # modern netstat alternative
lsof -i :8080 # which app using port 8080
✅ HTTP Testing
curl google.com # fetch webpage
curl -I google.com # headers only
curl -v google.com # verbose debug
wget file.zip # download file
✅ SSH
ssh user@ip # connect server
ssh -i key.pem user@ip # connect using key
scp file user@ip:/tmp # copy file to server
scp user@ip:/tmp/file . # copy from server
✅ Advanced Debug (Powerful)
telnet ip 80 # test port manually
nc -zv ip 80 # port open check
tcpdump -i eth0 # capture packets
🧠 MUST-KNOW THEORY
Memorize:
OSI Model
Application
Presentation
Session
Transport
Network
Data Link
Physical
Important Ports
22 → SSH
80 → HTTP
443 → HTTPS
3306 → MySQL
5432 → PostgreSQL
6379 → Redis
🎯 Week 1 Final Practice (Real DevOps Tasks)
Do these WITHOUT Google:
✅ Install nginx
✅ Host webpage
✅ Check logs
✅ Kill high CPU process
✅ Fix permission denied
✅ Find which app using port
✅ Fix DNS issue
✅ Disk full cleanup
✅ Write auto-restart script
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- Other Apps
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