Rocky Linux
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đ These are Linux commands notes taken from the Rocky Linux docs, maybe I'll move them to a more Linux general section later.
Treat everything as a file.
Value portability.
Do one thing and do it well.
KISS: Keep It Simple Stupid.
"UNIX is a simple operating system, but you have to be a genius to understand the simplicity." (Dennis Ritchie)
"Unix is user-friendly. It just isn't promiscuous about which users it's friendly with." (Steven King)
# command [option(s)] [argument(s)]
/bin/bash
cat /etc/passwd
cat /etc/shadow
cat /etc/profile
cat /etc/sudoers
apropos --exact password -a change
whatis clear
man clear
reboot
shutdown -r +5
shutdown now
shutdown -h 0:30
shutdown -h 0:30 "Server shutdown at 0:30"
shutdown --show
shutdown -c
history
clear
echo -ne "\t Hello \n"
echo $LANG
echo $PATH
date
date +%F
date +%x
date +%T
date -d 20250310 +%j
# Convert timestamp to a date
date -d "1970-01-01 20156 days"
# Convert date to timestamp
echo $(($(date --date="2025-01-25" +%s)/86400+1))
id root
whoami
who
who -r
pwd
cd
ls
ls -l
ls -ld
ls -lX
ls -g
ls -dl
ls -lah
ls -ltr
ls -lhS
ls -lhR
ls -liah
ls -lAhR
ls -lhR /var/ | grep ^\- | grep -E "[1-9]*\.[0-9]*M"
alias
ll
du -sh /etc
mkdir -p /tmp/newdir/newsubdir
touch file
touch -t [AAAA]MMJJhhmm[ss] file
rmdir /tmp/newdir/newsubdir
rm file
rm -r dir
rm -rf dir/files
rm -f -- -file
mv file1 file2
mv file1 file2 /tmp
cp file1 file2
cp file /tmp
cp -pr dir1 dir2
file /etc/passwd
more /etc/passwd
less file1
/text # search
g or G # first/last page
cat /etc/passwd
cat -n /etc/passwd
cat -b /etc/profile
cat /etc/passwd /etc/group
tac /var/log/messages | less
head -n 20 /etc/profile
tail -n 20 /etc/profile
tail -f /var/log/messages
sort -k 3,4 -t ":" -n /etc/passwd
sort -u FILE
sort FILE | uniq
sort -nr ips.txt
sort -hr size.txt
wc -c
wc -l
find /tmp -name *.txt -exec rm -f {} \;
find /tmp -name *.txt -delete
find /var -size +1M -a -size -1024M -a -type f -exec ls -lh {} \;
whereis ls
which ls
grep "root*" /etc/passwd
grep -w "root:" /etc/passwd
grep -w "^root" /etc/passwd
grep -i version /etc/os-release
grep -iv version /etc/os-release
grep -R "systemd" /var/log/# Input redirection
ftp -in serverftp << ftp-commands.txt
wc -l /etc/profile
wc -l < /etc/profile
# Output redirection
date +%F > date_file # overwrite
date +%F >> date_file # append
# stderr output redirection
ls -R / 2> errors_file
ls -R / >> ok_file 2>> nok_file
ls -R / >> log_file 2>&1
ls -R / 2>> /dev/null
# Copy stdin to file and to stdout
cat /etc/os-release | tee release
# Pipes
ls -lia / | head
ls -lia / | tail
ls -lia / | sort
ls -lia / | wc
ls -lia / | grep etc
ls -lia / | tee list
# Aliases
alias
cat .bashrc # permanent user's aliases file
cat /etc/bashrc # all users file
type ls
ls
\ls
mount | column -t
ls /; cd /home; ls -lia; cd /sort firstnames.txt | uniq
sort firstnames.txt | uniq -cd
xargs ls -ld
/home
/tmp
<CTRL+D>
xargs -L 1 find /var/log -name
xargs -n 1 find /var/log -name
find /var/log/ -name "*.log" -mtime -1 | xargs tar cvfP /root/log.tar
mkdir /tmp/backup && find /var/log -type f -name "*.log" | xargs -I % cp % /tmp/backup
watch
watch -n 5 tail -n 5 /var/log/secure
watch -n 1 'ls -l | wc -l'
watch -t -n 1 date
install -d /tmp/samples
install /tmp/test.txt /tmp/samples/
install -v -o syselement -g users -m 644 -D -t /tmp/samples/ /tmp/test.txt
install -v -b -S ".bak" -D -t /tmp/samples/ /tmp/test.txt
tree
tree -ah
tree -hugp /etc/security/
stat /var/log/messages# yum/dnf
# yum-utils / dnf-utils package
dnf install dnf-utils
repoquery
repoquery -l yum-utils
rpm -ql yum-utils # same
yumdownloader --destdir /var/tmp/ --resolve samba
dnf download --downloadonly --downloaddir /var/tmp --resolve samba # same
# pmisc package
pstree
killall nc
fuser# Files
/etc/passwd
/etc/shadow
/etc/group
/etc/gshadow
/etc/skel/
/etc/default/useradd
/etc/login.defs# Groups
cat /etc/group
cat /etc/gshadow
groupadd -g 1020 group1
# Debian
addgroup
groupmod -g 1022 group1
groupmod -n group3 group2
sudo find / -gid 1020 -exec chgrp 1022 {} \;
groupdel group1
# root GID = 0
gpasswd -a user2 group1
gpasswd -d user2 group1
echo $SHLVL ; echo $BASH_SUBSHELL
newgrp group1 # child shell with temp group1# Users
# root (uid=0) - system admin
# system users (uid=201~999)
# regulare users (uid>=1000)
cat /etc/passwd
cat /etc/shadow
# ! For each line in the /etc/passwd file there must be a corresponding line in the /etc/shadow file.
# default settings
ls -lah /etc/skel/ # file templates for new user home dir
cat /etc/login.defs
cat /etc/default/useradd
useradd -D # shows /etc/default/useradd contents
useradd user1 # defaults from /etc/default/useradd
useradd -N user1 # no user group, uses the default (users:100)
useradd -u 1002 -g 1020 -d /home/user user2
passwd user1
tail -n 2 /etc/passwd
tail -n 2 /etc/shadow
tail -n 2 /etc/group ; tail -n 2 /etc/gshadow
# Debian
adduser
deluser
usermod -u 1005 user1
usermod -L user2 # lock user
usermod -G user1 user2
userldel -r user1 # deletes user's home dir, mail files and primary group
# File owners
chown user1 file
chown :group1 file
chown user1:group1 file
chown -R -v user1:group1 /tmp/dir
chown --reference=./file2 file
chgrp group1 filepasswd
passwd user1
passwd -S user1
passwd -l user1 # lock user
passwd -u user1 # unlock user
sudo echo "p@ssw0rd" | passwd --stdin user1 # default pw, e.g. in scripts
chage user1
chage -m 60 -M 90 -W 80 -I 10 user1 # pw expire
su # login as root
su - user1 # - = -l = make the shell a login shell
su - root -c "cat /etc/shadow"/
Contains special directories
/boot
Files related to system startup
/sbin
Commands necessary for system startup and repair
system binaries
/bin
Executables of basic system commands
binaries
/usr/bin
System administration commands
/lib
Shared libraries and kernel modules
libraries
/usr
Saves data resources related to UNIX
UNIX System Resources
/mnt
Temporary mount point directory
mount
/media
For mounting removable media
/misc
To mount the shared directory of the NFS service.
/root
Administrator's login directory
/home
The upper-level directory of a common user's home directory
/tmp
The directory containing temporary files
temporary
/dev
Special device files
device
/etc
Configuration and script files
editable text configuration
/opt
Specific to installed applications
optional
/proc
This is a mount point for the proc filesystem, which provides information about running processes and the kernel
processes
/var
This directory contains files which may change in size, such as spool and log files
variables
/sys
Virtual file system, similar to /proc
/run
That is /var/run
/srv
Service Data Directory
service
ls -lah /dev/
# (Standard) Partitions
cat /proc/partitions
fdisk -l
fdisk -l /dev/nvme0n1
cfdisk /dev/nvme0 # optimized, to managed partitions
parted
parted -l /dev/nvme0
gparted # GUI
lsblk
dmsetup ls
# Disk preparation steps (no LVM)
# 1. Physical disk setup
# 2. Volumes partitioning
# 3. File systems creation
# 4. File systems mounting
# 5. User access managementLVM STORAGE MECHANISMS
Performance
Redundancy
Space Efficiency
Use Case
Linear
Normal
â No
â High
Basic storage growth
Striped
â High
â No
â High
Fast I/O, performance
Mirrored
Moderate
â Yes
â Low
Data safety, critical use
# LVM - Logical Volume Manager
# PV (Physical Volume): Raw storage (disk/partition)
# PE (Physical Extent): Chunk of space in PVs
# VG (Volume Group): Pool of storage from PVs
# LV (Logical Volume): Usable partitions created from VG
# FS (File System): each LV can be formatted (ext4, xfs, ...)
# PV commands
pvscan
pvcreate
pvdisplay
pvremove
pvs
# VG commands
vgscan
vgcreate
vgdisplay
vgremove
vgextend
vgreduce
vgs
# LV commands
lvscan
lvcreate
lvdisplay
lvremove
lvextend
lvreduce
lvs
# DISK PREPARATION
# 0. Prepare Physical disk and Partitions (if necessary)
# check for existing LVM volumes
pvs
vgs
lvs
# Wipe nvme0n2 disk - WIPES ALL LVM/DATA/HEADERS!
wipefs --all --force /dev/nvme0n2
dd if=/dev/zero of=/dev/nvme0n2 bs=1M count=100
# dd if=/dev/zero of=/dev/nvme0n2 bs=1M status=progress
# ^^^ OWERWRITES ENTIRE DISK (SLOW) ^^^
hexdump -C /dev/nvme0n2 # should be clean
# Create new GPT partition table on disk nvme0n2
parted /dev/nvme0n2 mklabel gpt
# create single primary partition on disk nvme0n2
parted /dev/nvme0n2 mkpart primary 1MiB 100%
fdisk -l /dev/nvme0n2
# Disk /dev/nvme0n2: 5 GiB, 5368709120 bytes, 10485760 sectors
# Disk model: VMware Virtual NVMe Disk
# Units: sectors of 1 * 512 = 512 bytes
# Sector size (logical/physical): 512 bytes / 512 bytes
# I/O size (minimum/optimal): 512 bytes / 512 bytes
# Disklabel type: gpt
# Disk identifier: 34A69BE9-CA31-4ADC-B30A-AE22BB47A281
#
# Device Start End Sectors Size Type
# /dev/nvme0n2p1 2048 10483711 10481664 5G Linux filesystem
# ------ 1. LVM Physical Volume (no partitions case) ------
lsblk
pvcreate /dev/nvme0n2p1
pvdisplay /dev/nvme0n2p1
# --- NEW Physical volume ---
# PV Name /dev/nvme0n2p1
# VG Name
# PV Size <5.00 GiB
# Allocatable NO
# PE Size 0
# Total PE 0
# Free PE 0
# Allocated PE 0
# PV UUID b6bQp6-57SG-vTST-wu3r-F2r7-z5ML-FHHV8W
# ------ 2. LVM Volume Group ------
vgcreate vol2 /dev/nvme0n2p1
vgdisplay /dev/vol2
# --- Volume group ---
# VG Name vol2
# System ID
# Format lvm2
# Metadata Areas 1
# Metadata Sequence No 1
# VG Access read/write
# VG Status resizable
# MAX LV 0
# Cur LV 0
# Open LV 0
# Max PV 0
# Cur PV 1
# Act PV 1
# VG Size <5.00 GiB
# PE Size 4.00 MiB
# Total PE 1279
# Alloc PE / Size 0 / 0
# Free PE / Size 1279 / <5.00 GiB
# VG UUID cGPnl2-e1Xx-JF7l-uS8r-KmAa-NwX9-LLcxFo
# ------ 3. LVM Logical Volume ------
# lvcreate -L 5G -n lv2 vol2
lvcreate -l 100%FREE -n lv2 vol2
lvdisplay /dev/vol2/lv2
# --- Logical volume ---
# LV Path /dev/vol2/lv2
# LV Name lv2
# VG Name vol2
# LV UUID DZ3CCM-twpf-arLX-JYt7-9BQE-zoKq-Os5NxE
# LV Write Access read/write
# LV Creation host, time rockyvm, 2025-05-01 10:00:40 +0200
# LV Status available
# # open 0
# LV Size <5.00 GiB
# Current LE 1279
# Segments 1
# Allocation inherit
# Read ahead sectors auto
# - currently set to 8192
# Block device 253:2
# ------ 4. File System creation/mounting ------
# ext2, ext3, ext4, FAT16, FAT32, NTFS, HFS, BtrFS, JFS, XFS, ...
mkfs -t xfs /dev/vol2/lv2
blkid /dev/vol2/lv2
# /dev/vol2/lv2: UUID="fc6f54cc-e718-45e4-9620-169bdcd143ce" TYPE="xfs"
mkdir -p /mnt/lv2
echo 'UUID=fc6f54cc-e718-45e4-9620-169bdcd143ce /mnt/lv2 xfs defaults 0 2' | tee -a /etc/fstab
systemctl daemon-reload
mount -a
df -hT /mnt/lv2
# Filesystem Type Size Used Avail Use% Mounted on
# /dev/mapper/vol2-lv2 xfs 5.0G 68M 4.9G 2% /mnt/lv2
# Final check Disk -> PV -> VG -> LV -> FS
echo "=== LVM ===" && pvs && vgs && lvs && echo "=== Disks ===" && lsblk -f && echo "=== Mounts ===" && findmnt# Boot sector -> Super Block -> inodes table -> Data block
# In Linux, everything is a file.
# Linux meets the FHS (Filesystems Hierarchy Standard)
man hier
# Check file system consistency - partition must be UNmounted
umount /mnt/lv2
fsck -V /dev/vol2/lv2
xfs_repair -v /dev/vol2/lv2
# Mount point automatically mounted at boot time
cat /etc/fstab
# /dev/mapper/rl-root / xfs defaults 0 0
# UUID=652d402b-d797-4b8f-94f1-ba39a3537811 /boot xfs defaults 0 0
# /dev/mapper/rl-swap none swap defaults 0 0
# UUID=fc6f54cc-e718-45e4-9620-169bdcd143ce /mnt/lv2 xfs defaults 0 2
# UUID = Universally Unique Identifier
lsblk -o name,uuid
# Mount all filesystems mentioned in /etc/fstab
systemctl daemon-reload
mount
mount -a
# mounted info written to /etc/mtab
cat /etc/mtab
mount
man 8 mount
# mount -o defaults = mount -o rw,suid,dev,exec,auto,nouser,async
umount /mnt/lv2
# e.g. Temporary mount
mkdir -p /mnt/usb
mount -t vfat /dev/sdb1 /mnt/usb
cd /mnt/usb/
umount /mnt/usb# ------ File naming ------
mkdir "dir_1"
touch .hidden_file
# .c : source file in C language
# .h : C and Fortran header file
# .o : object file in C language
# .tar : data file archived with the tar utility
# .cpio : data file archived with the cpio utility
# .gz : data file compressed with the gzip utility
# .tgz : data file archived with the tar utility and compressed with the gzip utility
# .html : web page
ls -liah /usr/bin/passwd
# 9317257 -rwsr-xr-x. 1 root root 32K May 15 2022 /usr/bin/passwd
# 1 2 3 4 5 6 7 8 9
# 1 Inode number
# 2 File type (1st character of the block of 10). "-" = ordinary file
# 3 Access rights (last 9 characters of the block of 10)
# 4 Directories: entry/subdirs count. Files: hard link count (1 = single link)
# 5 Owner name
# 6 Group name
# 7 Size (byte, kilo, mega)
# 8 Date of last update
# 9 Name of the file
# ------ 7 File types in GNU/Linux ------
# . Current directory
# .. Parent directory
# - Regular file (text, binary, data, compressed)
# d Directory
# b Block device (disks, USBs)
# c Character device (keyboard, mouse)
# s Socket (network IPC)
# p Pipe/FIFO (inter-process communication). FIFO = First-In-First-Out
# l Symbolic/soft/hard link (like a shortcut)
ls -ld
# dr-xr-x---. 3 root root 4096 May 1 11:57 .
ls -la
# dr-xr-x---. 3 root root 4096 May 1 11:57 .
# dr-xr-xr-x. 18 root root 235 Mar 9 14:37 ..
ls -l /dev/nvme0n1
# brw-rw----. 1 root disk 259, 0 May 1 09:29 /dev/nvme0n1
ls -l /dev/tty
# crw-rw-rw-. 1 root tty 5, 0 May 1 08:28 /dev/tty
ls -l /etc/grub2.cfg
# lrwxrwxrwx. 1 root root 22 Mar 18 12:41 /etc/grub2.cfg -> ../boot/grub2/grub.cfg
# ------ e.g. Soft and Hard links ------
touch original.txt
# Create a soft (symbolic) link
ln -s original.txt softlink.txt
ls -l
# -rw-r--r--. 1 root root 0 May 1 17:59 original.txt
# lrwxrwxrwx. 1 root root 12 May 1 18:00 softlink.txt -> original.txt
# Delete original file, soft link breaks
rm original.txt
ls -l
# softlink.txt points to nothing (broken, in red)
# Create a hard link
touch fileA
ln fileA hardlinkA
ls -li
# Same inode, hardlinkA and fileA are indistinguishable
# 8835024 -rw-r--r--. 2 root root 0 May 1 18:02 fileA
# 8835024 -rw-r--r--. 2 root root 0 May 1 18:02 hardlinkA
# Remove one, the other still works
rm fileA
cat hardlinkA
# File content still exists
# Hard link to directories is not allowed# ------ File attributes ------
# Basic file/directory permissions
# r / 4 = read (file: view, dir: list)
# w / 2 = write (file: edit, dir: create/delete)
# x / 1 = execute (file: run, dir: cd into)
# - / 0 = no right/access
ls -l # -rwxr-xr--
# ââââ´âââ´ââ owner, group, others
# User types
# u = owner
# g = owner group
# o = others users
# a = all (u+g+o)
# ------ Octal representation ------
# USER GROUP OTHER
# +--------+ +--------+ +--------+
# Read (r) | 4 | | 4 | | 4 |
# Write(w) | 2 | | 0 | | 0 |
# Exec (x) | 1 | | 1 | | 1 |
# +--------+ +--------+ +--------+
# Total: 4+2+1 = 7 4+0+1 = 5 4+0+1 = 5
# Octal permission: 755 â rwxr-xr-x
chmod 755 file.sh
# rwxr-xr-x
chmod -R 644 /data
# recursive, files: rw-r--r--
# ------ Symbolic representation ------
# Who? Symbol
# ---------------------
# User u
# Group g
# Other o
# All a
#
# Operation Symbol
# ---------------------
# Add +
# Remove -
# Replace =
#
# Rights Symbol
# ---------------------
# Read r
# Write w
# Execute x
chmod u+x file
# add execute to owner
chmod u+rwx,g+wx,o-r file
# remove write from group, read from others
chmod -R a=r folder/
# add read for all recursively
# ------ Rights and mask (default permissions) ------
# Default Permissions Calculation
# --------------------------------------------------------------------------------
# | Type | Max Rights | Umask | Effective Rights | -x Bits | Final Rights |
# |------------|------------|-------|------------------|---------|---------------|
# | Directory | 777 | 022 | 755 (rwxr-xr-x) | - | 755 |
# | File | 666* | 022 | 644 (rw-r--r--) | remove x| 644 |
# --------------------------------------------------------------------------------
#
# * Note: Max rights for files is 666 (rw-rw-rw-) because execute (x) is not granted
# by default when creating a file, for security reasons.
#
# Explanation:
# - Max Rights: theoretical full permissions (777 for dirs, 666 for files)
# - Umask: subtracts permission bits (e.g. 022 removes write for group/others)
# - -x Bits: execution bits are removed from files even if umask allows them
# - Final Rights: resulting permissions on creation
umask
man umask
help umask
# 0022 = permissions 755 (rwxr-xr-x)
umask -S
# u=rwx,g=rx,o=rx - symbolic/file rights
# e.g.
umask 027
# new files for current session: 640, dirs: 750
touch test.txt
ls -l test.txt
# -rw-r-----
# /etc/login.defs file defines the default UMASK
grep -Ri umask /etc/login.defs
# Config persistence for custom umask
# ~/.bashrc (particular user)
# /etc/bashrc and /etc/profile (all users)
# ^^^ these overrides the umask parameter of /etc/login.defs# PID = Process IDentifier
# PPID = Parent Process IDentifier
# "init" process = father of all processes
# Parent/Child relationship between processes
ps
ps -ef
ps -fu root
# Show processes in the same session (process group)
ps -g $(ps -o sess= -p $$)
# Show processes associated with a specific terminal (e.g., pts/0 or tty1)
ps -t pts/0
# Show process info for a specific PID (replace 1234 with actual PID)
ps -p 1234
# Display processes in a hierarchical tree structure (parent/child)
ps -H
# Long format: includes PPID, priority, nice, etc.
ps -l
ps -f
# Sort by memory usage (descending)
ps aux --sort=-%mem
# Show headers on each paginated page (useful with 'less')
ps aux --headers | less
# Custom output format: show PID, UID, and command
ps --format "pid,uid,cmd"
ps -e --format "%P %p %c %n" --sort ppid --headers
# PPID PID COMMAND NI
# 0 1 systemd 0
# 0 2 kthreadd 0
# 1 629 systemd-journal 0
# 1 643 systemd-udevd 0
# 1 724 auditd -4
# 1 757 dbus-broker-lau 0
# 1 765 firewalld 0# ------ Process types ------
# User process:
# - Started from terminal
# - Linked to a user session
# - Accesses resources via system daemons
#
# Daemon (System process):
# - Started by system (boot time)
# - No controlling terminal (TTY)
# - Owned by system/root
# - Often ends in 'd' (e.g., sshd, systemd)
# DAEMON = Disk And Execution MONitor
# ------ Permissions & rights ------
# When a user runs a command:
# - Real UID/GID = user ID
# - Effective process UID/GID = same as real UID/GID
#
# If SUID/SGID is set on a command:
# - Effective process UID/GID = owner/group of the commmand file
# - Real UID != Effective UID
# - Used for privileged commands (e.g., passwd)
# ------ Process states ------
# ready - waiting for CPU time slice/process availability
# running/in execution - actively using CPU
# suspended - waiting for I/O
# stopped - paused by signal (e.g., SIGSTOP), waiting for a signal
# zombie - request for destruction
# dead - terminated by the parrent process
# orphan - child of dead parent process, adopted by init
# ------ Process exit sequence ------
# On termination:
# - Closes all open files
# - Frees allocated memory
# - Sends signal to parent (SIGCHLD)
# - Orphaned children processes get adopted (and eventually destroyed) by init (PID 1)
# ------ Priorities and scheduling ------
# Real-time processes:
# - Priority range: 0â99
# - Scheduled with real-time scheduling algorithms
#
# Normal/ordinary processes:
# - Priority range: 100â139 (dynamic)
# - Scheduled by Completely Fair Scheduler (CFS)
#
# Nice value - to adjust the priority of an ordinary process:
# - Range: -20 (high priority) to 19 (low)
# - Default: 0
nice -n 10 ./myscript.sh # run with adjusted priority
# ------ Execution modes ------
# Synchronous:
# - Shell waits until command completes
# - Must wait the end of the process for command prompt
# Asynchronous:
# - Shell returns prompt immediately
# - Use '&' to run in background
sleep 5 &
# Constraints for async:
# - Must not wait for user input
# - Should not output to terminal
# - Will terminate when shell exits unless disowned or protected (e.g., nohup)
# Sends a signal to a process by PID
pidof bash
kill -9 23998
kill -19 23999
# Common signals:
# 2 SIGINT - Interrupt (Ctrl+C)
# 9 SIGKILL - Force kill
# 15 SIGTERM - Graceful stop
# 18 SIGCONT - Resume
# 19 SIGSTOP - Suspend (Ctrl+Z)
# List all signals
man 7 signal
# Run process immune to hangup (connection logout)
nohup ./myprogram.sh 0</dev/null &
# ------ Ctrl+Z ------
# synchronous process suspended, returns control to shell
# ------ & Asynchronous execution ------
# Run command in background
time ls -lR / > list.ls 2> /dev/null &
# [job_number] PID
# fg [job] â bring job to foreground
# bg [job] â resume suspended job in background
fg 1
# CTRL+Z a synchronous process, then place it in the background
bg 1
# Lists background jobs and their status
jobs
# [1]- Running sleep 1000
# [2]+ Stopped find /
# Start a command with adjusted priority (niceness)
nice -n -5 find / -name "file" # Higher priority
nice -n 5 find / -name "file" # Lower priority
nice find / -name "file" # Default (niceness = 10)
# Limits file
cat /etc/security/limits.conf
# Change priority of a running process
renice -n 15 -p 24156
# Example using xargs:
pidof sleep | xargs renice -n 20
# Real-time process monitor
top
# pgrep â find PID(s) by name
pgrep -u root sshd
# pkill â send SIGTERM (default) signal to process by name
pkill tomcat
# Kill user session according to the terminal number
pkill -t pts/1
# Kill all processes with a given name
killall tomcat
# Show process tree
pstree -pnhu
# Orphan: parent dies -> init (PID 1) adopts child
# Zombie: child exits but parent has not reaped it
# Check for zombies:
ps -lef | awk '{print $2}' | grep Z
# Process state codes:
# D - uninterruptible sleep
# R - running/runnable
# S - sleeping
# T - stopped
# t - traced (debug)
# Z - zombie
# X - deadCtrl + A # Move to the start of the line.
Ctrl + E # Move to the end of the line.
Ctrl + U # Delete from the cursor to the start of the line.
Ctrl + K # Delete from the cursor to the end of the line.
Ctrl + W # Delete the word before the cursor.
Ctrl + L # Clear the terminal screen.
Ctrl + C # Stop the current process/command.
Ctrl + D # Log out or exit the terminal.
Ctrl + Z # Pause the current process (can be resumed).
Ctrl + R # Search command history (backward search).
Up Arrow # Show the previous command (from the command history).
Down Arrow # Show the next command (from the command history).
!! # Repeat the last command.
!n # Repeat the nth command from history.
Tab # Auto-complete commands, files, or directories.
Tab twice # List all possible completions.
Ctrl + Shift + C # Copy the selected text or command.
Ctrl + Shift + V # Paste copied text or command.
Ctrl + Shift + N # Open a new terminal window.
Ctrl + Shift + T # Open a new tab in the terminal.
Ctrl + Tab or Ctrl + PageDown # Switch between terminal tabs.vi
