Commands¶

LVM¶

LV/VG/PV

Get more info about LVM¶

Display and show Physical Volumes

pvs
pvdisplay [-s] <pv-name>

Display and show Volume Groups

vgs
vgdisplay [-s] <vg-name>

Display and show Logical Volume

lvs
lvdisplay <lv-name>

Steps to add a physical disk or new partition to LVM¶

lsblk -f
df -Th
fdisk /dev/sda
F
n
l
find 8e (lvm)
t
8e (lvm)
w
mkfs.ext4 /dev/sdb[x]
pvcreate /dev/sdaX
vgextend vg-name /dev/new-partition
lvextend -L [final-partition-size] /dev/VGname
lvextend -L 99G /dev/ubuntu1804-vg/root
resize2fs /dev/vg-name/lv-name

Create a new Logical Volume¶

Create a new Logical Volume

sudo lvcreate -n <LV name> -l <LV-size> <VG name>
sudo lvcreate -n new-lv    -l 100%FREE  vg-name

Make a filesystem for it

sudo mkfs.ext4 /dev/exists-vg/new-lv

Temporary mounting

Mount it to wherever you want

sudo mount /dev/exists-vg/new_lv /mnt/new_dir

Permanent mounting

Append this line of code to /etc/fstab

/dev/exists-vg/new_lv   /mnt/dir   [ext4 | btrfs]   defaults   0   2

LVM snapshot¶

lvcreate -v -L -s -n backup /dev/vg-name

write a new partition on disk¶

# Check the free space and partitions with mount point
lsblk
df -h

# Create a new partition on the disk
fdisk /dev/sd{a..z}
n
p / e
choice partition number
choice partition first sector
choice partition last sector
w
mkfs.ext4 /dev/sd{a..z}{1..n}

Mount Option¶

# Show mounted partitions
fdisk -l
mount | column -t
df -h

# findmnt
findmnt -l
findmnt -D
findmnt --fstab /home

# Mount temporary
mount /dev/sd{a..z}{1..n} /xyz

# Mount permanently via fstab
1. Add new disk (usually /dev/sdb)
2. Create new partition on disk
3. Format partition with new FS (mkfs.ext4 /dev/sdb[x])
4. Mount a specific path to new partition
5. Edit `fstab` for mount permanently

Get partition info¶

List of partitions and mounted path

lsblk

List of ID and UUID of devices

blkid

Get the list of a partition

tune2fs -l /dev/sda2

# Filesystem volume name
# Last mounted on
# Filesystem UUID
# Filesystem magic number
# Filesystem revision
# Filesystem features

Change left root password¶

# Mount chroot shell - change password
1. Boot the Ubuntu Live CD.
2. Press Ctrl-Alt-F1
3. sudo mount /dev/sda1 /mnt
4. If you created a custom partition layout when installing Ubuntu you have to find your ‍root partition using the `fdisk -l` utility. See the section Finding your root partition.
5. sudo chroot /mnt

Users and Groups¶

Users¶

Difference between useradd and adduser:

useradd is native binary compiled with the system. But, adduser is a perl script which uses useradd binary in back-end.

adduser is a perl script and more user friendly and interactive than its back-end useradd. There's no difference in features provided.

adduser is a wrapper for useradd

Add user¶

# Add a new user with home directory
useradd -m mehrdad

# Add a new user with group and default shell
useradd -m mehrdad -g mehrdadgrp -s /bin/zsh

# Delete an existing user with home folder
userdel -r mehrdad

# List of users that user has already added
groups mehrdad

Changing owner¶

# Change owner of file
chown user_name file_name

# Change group and user owner:
chown group_name:user_name file_name

# change owner/group of a directory
sudo chown -R username:group <directory-name>

Lock and Unlock an user¶

# automatically
usermod -L mehrdad
usermod -U mehrdad

# manually
vim /etc/passwd
root:x:0:0:root:/root:/sbin/nologin
root:x:0:0:root:/root:/usr/sbin/nologin

Kill user in another session¶

ctrl + alt + f2
pkill -9 -u USER || ps -fp $(pgrep -d, -u USERNAME)

Grep all active users¶

sudo cat /etc/passwd | egrep "bash$"

check user exists¶

getent passwd root

Groups¶

# Add a new group
grpadd

# Add an existing user to a specific group
usermod -aG grp_name user_name
gpasswd -a user_name grp_name

# Change group owner of file
chgrp group_name file_name
chown :group_name file_name

Archive & Compression¶

TAR¶

# Create TAR file
tar -cf file-name.tar file/directory

# Extract tar.xz file
tar -xf 1.tar.xz

# Extract tar.gz file
tar -xvzf 1.tar.gz

# Extract tar.bz file
tar -xvf 1.tar.bz

XZ¶

# Add directory into the XZ compress file
tar cf - directory-name | xz -z > archive-name.tar.xz

# Create/Extract one file to XZ file
xz -z ramz.txt.gpg
xz -d ramz.txt.gpg.xz #

# Create `XZ` file into the another file
xz -z ramz.txt.gpg > ramz.txt.gpg.tar.xz

# Compress existed TAR file
xz --compress images.tar

GZ¶

# Add directory into the GZ compress file
tar cf - directory-name | gzip > archive-name.tar.gz

BZIP2¶

# Add directory into the BZ compress file
tar cf - directory-name | bzip2 > archive-name.tar.gz

systemd¶

Get the list of services(units)

systemctl list-units --type=service

Get the list of unit files

sudo systemctl list-unit-files --type=service

Add service to startup

sudo systemctl enable <service-name>

Mask service to prevent start

sudo systemctl mask <service-name>

UnMask service to prevent start

sudo systemctl unmask <service-name>

grep¶

GREP CheatSheet

# Reverse grep
grep -v

# count target
grep -c

# grep with line number
grep -n

# grep case insensitive
grep -i

# first line character
"^"

#end line character
"$"
or
-e
|

Remove the shared line from file 1¶

grep -Fxv -f file2.txt file1.txt > result.txt

-F برای استفاده از متن ساده (بدون regex)
-x برای تطبیق کامل خط
-v برای نمایش خط‌هایی که در فایل دوم نیستند
-f file2.txt برای مقایسه با محتوای فایل دوم

sed¶

sed switch¶

- s (substitute match pattern)
- g (global sub)
- 3g (after 3th character sub)
- -e (selected items)
- & (same characters)
- -i (save to file)
- -r (extended regex)
- #linenumber (each line that you want to apply sed)
- #` (each line that you don't want to apply sed)
- d (delete matched pattern)
- -p (print matched pattern)
- I (case ignore flag)

comm¶

Compare two sorted files line by line¶

Remove the sharing area from file one

comm -23 file1.txt file2.txt > result.txt

NOTE¶

Files must be sorted before, if didn't use this command

Schema of comm 23

comm -23 <(sort file1.txt) <(sort file2.txt) > result.txt

dos2unix¶

Cat the file to see the end-of-line characters

cat -A file1.txt

Convert \r\n to \n

dos2unix file1.txt

\r = Carriage Return (بازگشت هد چاپگر به ابتدای خط)
\n = Line Feed (حرکت هد چاپگر به خط بعدی)

sudoer¶

Add password-less sudoer

sudo bash -c 'echo "mehrdad ALL=(ALL) NOPASSWD:ALL" > /etc/sudoers.d/mehrdad'
sudo chmod 0440 /etc/sudoers.d/mehrdad

Verify it works

sudo -n whoami

Should print "root" without asking for password

force edit visudo¶

pkexec visudo

Monitor Resources¶

top
htop
btop
bpytop
uptime
iotop
vmstat
iftop

open ssl¶

Create a new CERT file via openssl

Create a new PrivateKey¶

openssl [key_type [genrsa]] -out /path/to/dir/self_priv_key.key 2048
or
openssl genpkey -algorithm RSA -out /path/to/dir/self_priv_key.key 2048

Create Self-Sign Cert with Private-Key¶

openssl req -x509 -new -days 3650 -key /path/to/dir/self_priv_key.key -out /path/to/dir/self_sing_cert.crt

Open CERT file to show content¶

openssl x509 -in made-cert.crt -text -noout

Open RSA PrivateKey file to show content¶

openssl rsa -in made-key.key -check

Create a self-sign Kubernetes ApiServer certificate¶

The private-key has been created before
we must use kubernetes valid CA (-CA ca.crt -CAkey ca.key)

openssl req -x509 -key /etc/kubernetes/ssl/apiserver.key -out /etc/kubernetes/ssl/apiserver.crt -days 365 -CA ca.crt -CAkey ca.key -subj "/CN=kubernetes" -addext "subjectAltName=DNS:kubernetes,DNS:kubernetes.default,DNS:kubernetes.default.svc,DNS:kubernetes.default.svc.cluster.local,DNS:lb-apiserver.kubernetes.local,DNS:localhost,DNS:node1,DNS:node1.cluster.local,DNS:node2,DNS:node2.cluster.local,DNS:node3,DNS:node3.cluster.local,IP:10.233.0.1,IP:172.16.2.10,IP:192.168.1.101,IP:127.0.0.1,IP:192.168.1.102,IP:192.168.1.103,IP:192.168.1.10"

curl¶

A ton of curl examples is here

# download with curl
curl -C - -L -O URL

# Explain arguments
-C, --continue-at <offset>
      Continue/Resume a previous file transfer at the given offset.
-L, --location
      (HTTP) If the server reports that the requested page has moved to a different location
-O, --remote-name
      Write  output to a local file named like the remote file we get.
'-',  Read from std-in

aria2¶

aria2c -c -s 16 -x 16 -k 1M -j 1 -i dl.txt

-c, --continue [true|false]
-s, --split=<N>
-x, --max-connection-per-server=<NUM>
-k, --min-split-size=<SIZE>
-j, --max-concurrent-downloads=<N>
-i, --input-file=<FILE>

Watch the OS installation date and time¶

stat -c %w /

Print Format Date¶

date +%<format-option>

date +"YEAR: %Y - Month: %m - Day: %d"

Check for Installed Libraries¶

ldconfig -p | grep <libname>

Set and Get from Clipboard¶

Bash/ZSHFish

sudo apt install xclip
alias pbcopy='xclip -selection clipboard'
alias pbpaste='xclip -selection clipboard -o'
source ~/.bashrc

sudo apt install xclip
alias pbcopy='xclip -selection clipboard'
alias pbpaste='xclip -selection clipboard -o'
source ~/.config/fish/config.fish

Test bpcopy command

echo 'go to my clipboard' | pbcopy

Watch these steps

![pic5][linux-commands-cheat-sheet]