Ubuntu-L2-Corporal

File Permissions & Ownership

chmod — Change file permissions

Changes file or directory permission bits. Controls read, write, and execute access.

$ chmod 644 file.txt

$ chmod +x script.sh

chown — Change file owner

Changes file owner and group. Requires root privileges.

$ sudo chown user:user logfile.txt

stat — Detailed file information

Displays detailed file metadata. Shows permissions, size, and timestamps.

$ stat logfile.txt

  File: logfile.txt
  size: 30        	Blocks: 8          IO Block: 4096   regular file
Device: 31h/49d	Inode: 430         Links: 1
Access: (0644/-rw-r--r--)  Uid: (  501/     csp)   Gid: ( 1000/     csp)
Access: 2026-02-04 20:22:37.252816950 -0500
Modify: 2026-02-04 20:22:35.421653163 -0500
Change: 2026-02-04 20:22:35.421653163 -0500
 Birth: 2026-02-04 20:21:32.777697977 -0500

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Process & System Control

ps — View running processes

Lists running processes. aux shows all users and full details.

$ ps
    
    PID TTY          TIME CMD
 121032 pts/0    00:00:00 bash
 121410 pts/0    00:00:00 ps

$ ps
    
    PID TTY          TIME CMD
 121032 pts/0    00:00:00 bash
 121410 pts/0    00:00:00 ps

top — Real-time process monitor

Shows real-time system processes. Updates CPU and memory usage continuously.

$ top

top - 20:56:04 up 11 days, 13:29,  1 user,  load average: 0.00, 0.00, 0.00
Tasks: 128 total,   1 running, 126 sleeping,   0 stopped,   1 zombie
%Cpu(s):  0.1 us,  0.1 sy,  0.0 ni, 99.8 id,  0.1 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :   3898.2 total,    411.4 free,    490.2 used,   3185.5 buff/cache
MiB Swap:      0.0 total,      0.0 free,      0.0 used.   3408.1 avail Mem

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
   4320 csp       20   0 1267348  23644  12432 S   0.3   0.6  33:32.27 containerd
 123638 csp       20   0   11168   5276   3144 R   0.3   0.1   0:00.01 top
      1 root      20   0   24780  14176   9944 S   0.0   0.4   1:12.87 systemd
      2 root      20   0       0      0      0 S   0.0   0.0   0:00.56 kthreadd

htop — Enhanced process viewer (install first)

Interactive and user-friendly process viewer. Supports mouse control and process tree.

$ sudo apt install htop

$ htop

kill — Stop a process by PID

Sends a signal to a process by PID. Commonly used to terminate processes.

$ kill 1234

pkill — Kill process by name

Kills processes by name. Faster than searching PID manually.

$ pkill firefox

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Networking Basics

ip a — Show IP addresses

Displays network interfaces and IP addresses. Replaces older ifconfig.

$ ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:55:55:37:74:5e brd ff:ff:ff:ff:ff:ff
    altname enx52555537745e
    inet 192.168.5.15/24 metric 200 brd 192.168.5.255 scope global dynamic eth0
       valid_lft 3522sec preferred_lft 3522sec
    inet6 fe80::5055:55ff:fe37:745e/64 scope link proto kernel_ll
       valid_lft forever preferred_lft forever

ping — Test network connectivity

Tests network reachability. Measures latency and packet loss.

$ ping google.com

PING google.com (142.250.137.102) 56(84) bytes of data.
64 bytes from 142.250.137.102: icmp_seq=1 ttl=64 time=1.27 ms
64 bytes from 142.250.137.102: icmp_seq=2 ttl=64 time=0.396 ms
64 bytes from 142.250.137.102: icmp_seq=3 ttl=64 time=0.403 ms
^C
--- google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2037ms
rtt min/avg/max/mdev = 0.396/0.688/1.266/0.408 ms

curl — Fetch data from a URL

Transfers data from URLs. Commonly used for APIs and HTTP testing.

$ curl ipconfig.io

174.89.144.10

wget — Download files

Downloads files from the internet. Works well for scripts and automation.

$ wget https://example.com/file.zip

--2026-02-04 20:59:41--  https://sample-files.com/downloads/compressed/zip/basic-text.zip
Resolving sample-files.com (sample-files.com)... 15.235.219.232
Connecting to sample-files.com (sample-files.com)|15.235.219.232|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 999 [application/zip]
Saving to: ‘basic-text.zip’

basic-text.zip                                        100%[=======================================================================================================================>]     999  --.-KB/s    in 0s

2026-02-04 20:59:42 (6.85 MB/s) - ‘basic-text.zip’ saved [999/999]

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Compression & Archives

tar — Create/extract archives

Creates or extracts archive files. Commonly used with gzip compression.

$ tar -czvf two.tar.gz two/

a two
a two/21
a two/21/file.txt

$ tar -xzvf two.tar.gz

x two/
x two/21/
x two/21/file.txt

zip — Create ZIP archives

Creates ZIP archive files. Widely supported across platforms.

$ zip three.zip file.txt logfile.txt

  adding: file.txt (deflated 27%)
  adding: logfile.txt (deflated 27%)

unzip — Extract ZIP files

Extracts ZIP archives. Preserves file structure.

$ unzip files.zip

Archive:  four.zip
  inflating: file.txt
  inflating: logfile.txt

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Disk & Hardware

lsblk — List block devices

Lists block storage devices. Shows disks, partitions, and mount points.

$ lsblk

NAME    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
vda     253:0    0   100G  0 disk
├─vda1  253:1    0    99G  0 part /
├─vda13 253:13   0   923M  0 part /boot
└─vda15 253:15   0    99M  0 part /boot/efi
vdb     253:16   0 294.7M  1 disk /mnt/lima-cidata

mount — Mount a filesystem

Attaches a filesystem to a directory. Makes storage accessible.

$ sudo mount /dev/sdb1 /mnt

umount — Unmount a filesystem

Detaches a mounted filesystem. Must be done before device removal.

$ sudo umount /mnt

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Terminal Productivity

clear — Clear terminal screen

Clears the terminal display. Does not delete command history.

$ clear

history — Show command history

Shows previously executed commands. Useful for command recall.

$ history

  168  ping google.com
  169  clear
  170  logut
  171  clear
  172  logout
  173  clear
  174  lsblk
  175  clear
  176  history

alias — Create command shortcuts

Creates command shortcuts. Improves productivity.

$ alias ll='ls -la'

csp@lima-default:/Users/csp/kact/lima-base$ alias ll='ls -la'
csp@lima-default:/Users/csp/kact/lima-base$ ll
total 36
drwxr-xr-x+  17 csp csp  544 Feb  4 21:03 .
drwxr-xr-x+ 291 csp csp 9312 Feb  3 15:32 ..
-rw-r--r--+   1 csp csp 3322 Jan 12 16:13 .ant
drwxr-xr-x+  12 csp csp  384 Jan 28 21:35 .git
-rw-r--r--+   1 csp csp 1969 Jan 12 16:13 .gitignore
-rw-r--r--+   1 csp csp    0 Jan 12 16:13 README.md
-rw-r--r--+   1 csp csp  999 Jul 15  2024 basic-text.zip
-rw-r--r--+   1 csp csp   30 Feb  4 20:41 file.txt
-rw-r--r--+   1 csp csp  360 Feb  4 21:02 four.zip
-rw-r--r--+   1 csp csp   30 Feb  4 20:22 logfile.txt
drwxr-xr-x+   3 csp csp   96 Feb  4 20:23 one
drwxr-xr-x+   3 csp csp   96 Feb  4 21:01 three
-rw-r--r--+   1 csp csp  360 Feb  4 21:02 three.zip
drwxr-xr-x+   3 csp csp   96 Feb  4 20:23 two
-rw-r--r--+   1 csp csp  504 Feb  4 21:00 two.tar.gz
drwxr-xr-x+   3 csp csp   96 Feb  4 20:23 two2
-rw-r--r--+   1 csp csp  217 Jan 12 16:13 ubuntu-20.04.yaml

watch — Run a command repeatedly

Runs a command at fixed intervals. Useful for live monitoring.

$ watch df -h

Every 2.0s: df -h                                                                                                                                                               lima-default: Wed Feb  4 21:04:36 2026

Filesystem      Size  Used Avail Use% Mounted on
tmpfs           390M  1.1M  389M   1% /run
efivarfs         56K  1.4K   55K   3% /sys/firmware/efi/efivars
/dev/vda1        96G  5.8G   91G   6% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock

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Text Editing & Input

nano — Terminal text editor

Simple terminal-based text editor. Beginner-friendly with on-screen help.

$ nano notes.txt

xargs — Build argument lists from input

Builds command arguments from input. Used in pipelines for batch operations.

$ cat file.txt | xargs rm

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User & Session Control

logout — End terminal session

Ends the current shell session. Logs the user out of the terminal.

$ logout

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