Essential Linux Commands- 2

Shortcuts:

Reverse Search

Ctrl + R then type the command you want to search then Tab

Commands:

Info of Command

# brief description of command
whatis cat

Real time process info

# Real time process
top

# Wrapper: Graphical
htop

List Process & Hierarchy

# List Process not a Real time
ps

# Detail process list
ps aux

# Process Hierarchy
pstree -p

# Port used by Process
lsof -i :8085

Inspect Network Connection

# Get active ports in Use
netstat -tuln

# Network Interface Info
ifconfig

# Network Troubleshoot (Can WireShark tool)
# enX0: Network Interface
sudo tcpdump -i enX0 port 80

# Test Connectivity
ping google.com

# Tarce the path packet to reach destination
traceroute google.com

Disk Space, Size & Memory

# Check Disk Space
df -h

# Size of dir or file
# opt: directory
du -sh opt

# Memory (RAM)
free -h

Services

• Systemd manages services

# Logs of Services
journalctl

# Particular Service
journalctl -u nginx

# Logs of services from Last Boot
journalctl -b

Logs Filter

# Last 10 line of logs
tail -n 10 /var/log/auth.log

# First 10 line of logs
head -n 10 /var/log/auth.log

Alias

alias detail_list='ls -la'

# Want to persist the Alias, add in '~/.bashrc'

Symbolic Link

• Soft Link (Like Windows Shortcuts)- It can be broken

    # ln: link
    # -s: flag for soft link 
    # myfile: file you want to crate soft link
    # slink: name of soft link file created
    ln -s myfile slink
  

• Hard Link (Actual Copy)- Doesn’t break the other one

    # ln: link
    # myfile: file you want to crate soft link
    # hlink: name of hard link file created
    ln myfile hlink
  

Refer Linux Journey

Linux Journey