ssh-keygen ssh-copy-id
ls cd directory/ cd ~ cd .. ls -l ls -lh ls -la cp file1 file2 mv file1 directory/ mv file1 file1newname mkdir folder rmdir folder/ rmdir -r folder/ rmdir -rf folder/ touch filename
find (realtime , powerful, slow) locate (search indexsnapshot , fast) which ( search $PATH only and gives you the full path , only executable files , fast) find directory | grep name
find . find -type d(directory) find -type f(file) find -type f -size +1M find -type f -size +1M -size -100M find -type f -size +100M find -type f -size +100M -delete find . -type f -size +1M -exex ls -lh {} ; find . -type f -size +1M -exex rm -rf {} ;
ext4 (stable, kernel support, usually default) Best choice ! zfs (snapshots, span drives, resizeable, proprietary-ish) btrfs ( linux native (next gen) file system, redhat in 2017 abandoned , SUSE supports) XFS ( good with large files, separate tools, getting old) RieserFS(was the next big thing, Dev went to prison, no body used it much)
diff file1.txt file2.txt diff -c file1.txt file2.txt md5sum *
watch -d -t -n 1 cat results.txt cat file.txt > results.txt cat file.txt >> results.txt cat someError.txt 2> results.txt cat someError.txt 2> results.txt 2>&1 wc (word count) -w file.txt wc -w <file.txt cat file.txt | wc -w
Globbing :
.
*.doc
file?.doc
Regex :
. = any character
- = zero or more of previous character ^ = beginnig of line $ = end of line \s = whitespace (space, tab, newline) | = OR [a-z,0-9] = or with range support .* = construct meaning zero or more of any character
Examples :
grep "chicken" file.txt grep "[Cc]hicken" file.txt grep "\scorn" file.txt grep "^chicken" file.txt grep "^[Cc]hicken" file.txt grep "corn$" file.txt grep "^chicken.*corn$" file.txt
tar -c -v- f archive.tar directory/ tar -xvf archive.tar
flags : -c : create -x : extract -v : verbose -f : filename (Has to be at the end like -cvf)
-z : tar -z -c -v- f archive.tar.gz directory/
-j : tar -j -c -v- f archive.tar.bz2 directory/
-J : tar -J -c -v- f archive.tar.xz directory/
gzip document.pdf => document.pdf.gz gunzip document.pdf.gz gzip can't archive a directory , It will compress every individual file in that directory separately!
zip file.zip document.pdf zip -r allfiles.zip directory/ unzip allfiles.zip
ln file.txt hardfile.txt ln -s file.txt softfile.txt ls -li
stat file.txt find . -samefile file.txt
type | user | group | other || owner | group affiliation | name
- or d r w x r w x r w x user group name
sudo chown root filename.txt sudo chgrp root filename.txt
sudo chown ehsan.ehsan filename.txt
sudo chmod ugo-x filename.txt sudo chmod u-x,g-x,o-x foldername/
if a directory is executable it means you can cd to that directory
r = 4 w = 2 z = 1 rw- = 6 -wx = 3 r-x = 5 --x = 1 -w- = 2 r-- = 4
chmod 666 filename.txt -rw-rw-rw- chmod 777 filename.txt -rwxrwxrwx chmod 751 filename.txt -rwxr-x--x
SUID = File : executable runs with owner permissions Folder : Nothing
GUID = File : executable runs with group permissions Folder : new files created with matching group membership
Sticky bit = File : Nothing Folder : files can't be deleted by non-owner
sudo chmod o+t shareddirectory/
cd /usr/share/doc
ls --help
man ls
whatis passwd
man 5 passwd
man -k
su = become root with password sudo command = run the command with root privilege sudo su = become root without password sudo visudo = Edit sudoers file and allow a user to execute any command without asking password sally ALL=(ALL:ALL) NOPASSWD:ALL
programs:
halt command
reboot command
shutdown command
systemd sysV
poweroff.target => runlevel 0 rescue.target => runlevel 1 multi-user.target => runlevel 3 graphical.target => runlevel 5 reboot.target => runlevel 6
as a root user :
systemctl get-default
systemctl set-default multi-user.target
systemctl isolate reboot.target
sudo nano /etc/default/grub
sudo update-grub
top (see what process using your CPU more than others)
ps -ef | grep dd (dd stands for name of that process)
kill 1750 (1750 stands for process id [PID])
as root user :
cd /var/log
grep ssh *
tail syslog tail -f syslog (it's realtime) tail -n (will show you the last 20 lines)
crontab -e (to edit)
/etc/crontab /etc/cron.d/* /etc/cron.hourly/ /etc/cron.daily/ /etc/cron.weekly/ /etc/cron.monthly/
as a root user :
nano /etc/crontab
cd /etc/cron.d/ nano popularity-contest
at now + 1 minute (Schedules future one-time event) at> echo "test" > results.txt at> echo "still testing" > results.txt
when you're done, press Ctrl + d
echo "another way" > way2.txt | at now + 1 minute
atq (shows the current queued items)
atrm 4 (Removes queued job 4)
1- looking to /var/log/syslog :
grep CRON /var/log/syslog
2- Email notification
By default, crontab jobs email the STDOUT and STDERR to the user
But :
crontab -e
35 6 * * * echo "Backups Completed" > /dev/null
"It's going to send an email to you ONLY if the task failed"
apt install apt remove apt update apt upgrade apt search apt info
If the package was installed before :
sudo rm /usr/bin/zipcloak
dpkg -S /usr/bin/zipcloak
zip
sudo apt purge zip
sudo apt install zip
If the package was Not installed before :
apt-file search /usr/bin/zipcloak
as a root user:
mount
cd /mnt/sda5
making some corruption :
dd if=/dev/zero of=/dev/sda5 bs=1k count=3
cd unmount /mnt/sda5 fsck /dev/sda5 yes yes yes yes mount /dev/sda5 /mnt/sda5
Another way:
restart press shift in grub menu at the end of line which starts with linux add this : fsck.mode=force press ctrl + X
as a root user :
free -h
memtester 8G 1
memtester 6200M 1 (should be free)
Another way:
restart press shift in grub menu select memory test 86+ (it will test all of the capacity of your RAM)
#!/bin/bash
for var in 1 2 3 4 OR [1..10] OR $(a linux command) do echo "loop $var" echo "loop complete" done
ps -eZ
cd /etc/apparmor.d/
nano /usr.sbin.cupsd
adduser testuser useradd -h (need flags) usermod -a for append -G to other groups userdel -rf
groupadd -h groupmod groupdel
All users : /etc/environment /etc/bash.bashrc /etc/profile
Individual : /home/user/.bashrc /home/user/.profile
/etc/skel
its only for new users
ulimit
hard limit (-H) : is the kernel-enforced maximum a user can set
soft limit (-S) : is the current limit which can be adjusted by user until hard limit is met
ulimit -Ha (current hard limits) ulimit -Sa (current soft limits)
ulimit -Sn 4000 (soft limit for open files)
nano /etc/security/limits.conf
/etc/pam.d/
pam-auth-update
you can use Network manager for it ! so simple :D
as a root user :
nano /etc/network/interfaces
auto eth0 iface eth0 inet dhcp
auto eth0 iface eth0 inet static address 10.10.10.20 netmask 255.255.255.0 network 10.10.10.0 broadcast 10.10.10.255 dns-nameservers 10.10.10.1 dns-search cbt
save and exit
service networking restart
ifconfig
as a root service:
systemctl name of service
enabled: will start on boot
disabled: will not start on boot
start: start service
stop: stop service
restart: restart (or start) service
status: show info about service
as a root user:
ping google.com
iptables -L
iptables -A OUTPUT -d 172.217.18.142 -j DROP
iptables -L
DROP all -- anywhere google.com
ping google.command
Operation not permitted
iptables -F
iptables -L
ping google.com
as a root user:
ifconfig
ping 192.168.1.1
route
ip route add 192.168.1.0/24 via 10.10.10.20 dev eth0
route
192.168.1.1
as a root user:
date
ntpdate
ntpdate 10.10.10.1
apt install ntp
nano /etc/ntp.conf
#pool 0.ubunto.pool.ntp.org iburst #pool 1.ubunto.pool.ntp.org iburst #pool 2.ubunto.pool.ntp.org iburst #pool 3.ubunto.pool.ntp.org iburst
END OF FILE :
server 10.10.10.1
save and exit
systemctl restart ntp
if your server has internet you can use this:
ntp server
as a root user :
cd /etc/bind
nano named.conf.options
acl clinets { 10.10.10.0/24 localhost; };
options { recursion yes; allow-query {clients; }; ... } save and exit
systemctl restart bind9
dig @localhost google.com
as a root user :
cd /etc/bind
named.conf.local
tail -f /var/mail/username
mail -s "test to bob" bob
sudo nano /etc/aliases
turtle: bob fish: root
save and exit
sudo newaliases
mail -s "test to fish" fish mail -s "test to fish" turtle
nano /etc/ssh/sshd_config
you can change the port number to listen on a diffrent port
OR
#Authentication PermitRootLogin yes => no OR prohibit-password
save and exit
systemctl restart ssh
sudo apt install squid
nano /etc/suid/squid.conf
TAG: cache_mem ... cache_mem 256 MB ... maximum_object_size_in_memory 2048 KB
save and exit
sudo systemctl restart squid.service
add localhost 3128 to proxy setting with firefox
ping google.com +> Network is unreachable
Manual proxy configuration on firefox > http proxy: server1 , port: 3128, check use this proxy server for all protocols
web browser > google.com access denied!
ssh root@server1
nano /etc/squid/squid.conf
under acl section:
acl bob src 10.10.10.10
#TAG http_access ... #http_access allow localhost
http_access allow bob
#And finally deny all other access to this proxy
http_access deny all
save and exit
sudo systemctl restart squid.service
web browser > google.com 200!
sudo apt install dovcot-imapd
netstat -tuna | grep LISTEN
configure thunder bird manually
cd /etc/dovecot/conf.d/
ls
sudo nano 10-ssl.conf
ssl = yes ssl_cert=</etc/ssl/certs/ssl-cert-snakeoil.pem ssl_ke=</etc/ssl/private/ssl-cert-snakeoil.key
save and exit
sudo systemctl restart dovecot
configure thunder bird manually
cd /lib/systemd/system
ls
cd /etc/systemd/system
ls
systemctl get-default > graphical.target
systemctl list-dependencies graphical.target > tree
cd graphical.target.wants
sudo systemctl enable ssh
sudo apt install apache2 php
cd /var/www/html
sudo mv index.html index.html.bak
sudo nano index.html
!!! TEST !!!
save and exit
Browse localhost
cd /etc/apache2/sites-available
ls
cp 000-default.conf fishlips.conf
nano fishlips.conf
ServerName fishlips
DocumentRoot /var/www/fishlips
save and exit
a2ensite fishlips
service apache2 reload
cd /var/www/fishlips
nano /etc/hosts
10.10.10.10 fishlips
save and exit
ping fishlips
browse http://fishlips
ifconfig
cd /etc/apache2/sites-available
ls
cp 000-default.conf
nano 000-default.conf
DocumentRoot /var/www/html
Require ip 10.10.10.10save and exit
systemctl reload apache2.service
browse localhost > 403 Forbidden
browse 10.10.10.10 > 200 Success
sudo apt install mariadb-server mariadb-client > E: Unable o locate package
sudo apt install mysql-server mysql-client
mysql -u root -p
Enter password:
mysql> show databases
docker run -d -p 8080:80 -v /root/config:/config linuxserver/nginx
docker ps
ls
cd config/ ls cd www/ ls rm index.html
nano index.html
It worked !
save and exit
browse localhost:8080
sudo apt install qemu-kvm libvirt-bin virt-manager
sudo virt-manager
-
Local install media
as a root user :
virsh list
virsh suspend generic(name)
virsh resume generic(name)
virt-install --name test --ram 512 --vcpu=1 --cdrom=/home/bob/dsl.iso --network=default / --disk path=/home/bob/testdisk/qcow,size=200,bus=ide,format=qcow2
ls /dev | grep sd
sudo fdisk /dev/sdb
m
p
n
p 1 2048 20971519
p
m
t
L
83
m
w
ls /dev | grep sd
ls /dev | grep sd
ls -l /sbin/mk*
mkfs.ext4 /dev/sdb1
swapon --show
cd /
dd if=/dev/zero of=/swapspace bs=1M count=500
mkswap /swapspace
swapon /sawpspace
chmod 0600 /swapspace
swapon --show
nano /etc/fstab
...
/swapspace none swap sw 0 0
save and exit
reboot
swapon --show
cd /mnt/
ls
showmount -e server1
nano /etc/fstab
...
/dev/sdb1 /mnt/disk auto defaults 0 0 server1:/opt/share/ /mnt/share nfs defaults 0 0
save and exit
mount -a
mount
1- create encrypted partition
2- decrypt (open) partition 3- format/use partition 4- re-encrypt (close) partition
as a root user:
apt install cryptsetup
ls /dev | grep sd
cryptsetup luksFormat /dev/sdb1
YES
Enter passphrase:
cryptsetup luksOpen /dev/sdb1 encrypted
Enter passphrase for /dev/sdb1:
ls /dev/mapper
mkfs.ext4 /dev/mapper/encrypted
mkdir /mnt/disk
mount /dev/mapper/encrypted /mnt/disk
cd /mnt/disk
touch testfile.txt
cd
umount /mnt/disk
cryptsetup lukeClose encrypted
ls /dev/mapper
cryptsetup luksOpen /dev/sdb1 myfiles
ls /dev/mapper
mount /dev/mapper/myfiles /mnt/disk
ls /mnt/disk
ls /dev | grep sd
pvdisplay
pvcreate /dev/sdb
pvdisplay
pvcreate /dev/sdc
pvcreate /dev/sdd
vgdisplay
vgcreate pool /dev/sdb /dev/sdc /dev/sdd
vgdisplay
lvdisplay
lvcreate -L 15G -n chunk pool
lvdisplay
ls /dev/mapper
mkfs.ext4 /dev/mapper/pool-chunk
ls /dev | grep sd
mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
cat /proc/mdstat
ls /dev | grep md
mksf.ext4 /dev/md0
mkdir /mnt/raid
mount /dev/md0 /mnt/raid
ls /mnt/raid
df -h
mdadm --detail --scan
mdadm --detail --scan . /etc/mdadm/mdadm.conf
as a root user :
ls / (looking for nfs )
ls /nfs
nano /etc/auto.master
...
#/misc /etc/auto.misc
/nfs /etc/auto.nfs
save and exit
nano /etc/auto.nfs
server server1:/nfs
save and exit
service autofs restart
ls /nfs/server
ls /nfs
mount
as a root user:
ls -l
rm important.conf > operation not permitted.
lsattr
chattr -i important.conf
rm important.conf
chattr +a file.txt
lsattr
echo "one more line" >> file.txt
echo "replace with this" > file.txt operation not permitted.
as a root user:
nano /etc/fstab
...
/dev/sdb1 /mnt/disk auto defaults,usrqouta 0 0
save and exit
umount /mnt/disk
mount /mnt/disk
mount
qoutacheck -au
qoutaon -a
edqouta bob
Filesystem blocks soft hard inodes soft hard
/dev/sdb1 0 500 1000 0 0 0
save and exit
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent