Ubuntu-L4-Lieutenant

Debugging & Inspection

1. strace — Trace system calls of a process

   strace ls

2. lsof — List open files and network connections

   lsof -i :8080

3. watch -n — Re-run a command at intervals

   watch -n 2 free -h

4. time — Measure command execution time

   time python script.py

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Networking & Remote Access

1. ssh — Secure remote login

   ssh user@server_ip

2. scp — Copy files over SSH

   scp file.txt user@server:/path

3. rsync — Fast file synchronization

   rsync -av src/ dest/

4. nc (netcat) — Network testing and debugging

   nc -zv localhost 80

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Permissions & Security

1. getfacl — View Access Control Lists

   getfacl file.txt

2. setfacl — Set Access Control Lists

   setfacl -m u:user:r file.txt

3. id — Show user/group IDs

   id

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Filesystem & Storage

1. mountpoint — Check if directory is mounted

   mountpoint /mnt

2. sync — Flush write buffers

   sync

3. fallocate — Preallocate file space

   fallocate -l 1G test.img

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Logs & Monitoring

1. journalctl — Query system logs

   journalctl -xe

2. dmesg — Kernel ring buffer messages

   dmesg | less

3. vmstat — Memory statistics

   vmstat 2

4. iostat — Disk I/O stats (install first)

   sudo apt install sysstat
   iostat

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Shell Power Tools

1. xclip — Clipboard access from terminal

   echo "text" | xclip -selection clipboard

2. column — Align output into columns

   column -t data.txt

3. select — Bash menu creation

   select opt in start stop exit; do echo $opt; break; done

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User & System Control

1. loginctl — Manage user sessions

   loginctl list-sessions

2. ulimit — Control resource limits

   ulimit -n

3. hostnamectl — Manage system hostname

   hostnamectl set-hostname mymachine

4. poweroff — Shut down system

   sudo poweroff

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