cheatsheet > Linux
Linux Professional Institute Certificate > LPIC-1
LPIC 1 TOPICS
A simple personal cheatsheet
Note: This document is not completed.
shell variables
export # export a VAR to sub shels and sob processe
psrintenv # list all variables on bash like $PATH, $HOME, $DISPLAY
unset VAR_NAME # drop VAR_NAME from bash
env # list all variables on bash like $PATH, $HOME, $DISPLAY
env VAR=value cmd # Run cmd with new value of VAR
echo $? # returns exit status code of last command
shell I/O
cat # prints a file to stdout
cat -b # prints non-blank numbered lines
cut -d <seprator> -f <col NO> /etc/passwd
# seprate a file with seprator and send specified column
echo # shows a msg or variable
less # show stdout in nice way, it should be piped after other commands
cmd1 ; cmd2 ; cmd3 # run multi commands
cmd1 && cmd2 # cmd2 runs if cmd1 runned success
cmd1 || cmd2 # cmd2 runs if cmd1 NOT runned success
cmd > filename # send output to filename (ovewwrite)
cmd >> filename # append output to filename
cmd < filename # send input data to cmd from filename
wc # print newline, word, and byte counts from std input or file (-l , -c, -w)
grep -i # find something from std input or file (-i for ignore case)
uniq # report or omit repeated lines
tr # Translate, squeeze, and/or delete characters from standard input
# Example
# $ sort < temp.txt | uniq -c | sort -nr
# 5 mina
# 3 ali
# 2 sara
# 2 reza
# 2 keyvan
# 1 jafar
sed 's/old/new/' # it replaces first old word of each line wiith new like vim
sed 's/old/new/g' # it replaces globaly
sed -E 's/old/new/' # it support regex
shell
# dir starting with / called absulute and without / called relative
# file namein linux is consist of full path (dirname + basename)
uname -a # display linux system info
hostname # display hostname (it shows ip with -i switch)
last reboot # it can show more things last {reboot, syslog, ...}
whoami # returns current user logged in
basename FILE # returns base name of file
dirname FILE # returns dir name of file
du -ha # shows disk usage by files in human readable
whereis # shows bin file of a cmd
which # where is executable file
head # open first lines of file (default 10 lines)
tail # open last lines of file (default 10 lines)
tail -f # open last lines of file in live mode (update changes)
ls -ltrha # list all files and folders time sorted reversed human readable mode
mkdir -p # make dirs with their parrents
cp -r # copy folders and its files recursively
stat filename # view Inode details
dd # make image byte by byte to a file
time CMD # calculate time for proccessing CMD
date # returns date and time
date +"%Y%m%d%H%M" # returns date and time formated
cal # show calendar
id # show the active user id with login and group
who # show who is logged on the system
w # like who with more details
users # list logged in users
pwd # returns current dir
touch # create file or update access time of file
gpg -c FILE # encrypt file
gpg FILE.gpg # decrypt file
ssh <username>@<host> -p1234
scp SOURCE_FILE user@host:DEST_FILE
expansion
* # anything with any length
? # anything with static kength in number of ? signs
[] # anything with one of chars in []
{} # all of args in {}
find
find . -iname foo\* # find NOT case sensative starting with foo files
find . -type d,l,f # find directorys , links and files
find . -size +1k # size of result is > 1kB
find . -exec CMD {} \; # execute a CMD on each result
# The commands run with the -exec are executed in the root directory of the
# find process. Use -execdir to execute the specified command in the directory
# where the match resides
find . -type f -inum 123456 # find files with Inode number
find . -type f -perm 0777 -print # all the files whose permissions are 777
find / -type f ! -perm 777 # Find all the files without permission 777
# -perm x777: x=
# 1: Sticky Bit, 2: SGID, /u=s: SUID, /g=s: SGID, /u=r: Read Only files,
# /a=x: all Executable files
# other switches:
# -atime, -ctime, -mtime # acces , change , modif fime bye day
# -amin, -cmin, -mmin # acces , change , modif fime bye minute
# -cmin -60: in last hour
find / -mtime +50 –mtime -100 # modified in 50-100 last days
# -maxdepth: directory depth, -not: return results do not matched
# find . -amine -4 # files has acces time less than 4 minutes
# find . -regex # find with regex pattern
# find /tmp -type d -empty #
find / -user root -name tecmint.txt # file owned by root
find / -size +50M -size -100M # Size between 50MB – 100MB
partitioning
fdisk # partitioning tool for MBR
gdisk # partitioning tool for GPT
#cmds : p , l L , m ? , n ,
mkfs -t /dev/sdb1 {vfat,ntfs,ext3} # format partitions
mkfs. -# + Tab key # shows all filesystems work with mkfs
blkid /dev/sdb1 # shows partition detalis
mount DEVICE MOUNT_POINT -o {rw,ro} # mounts a disk partition to a mount point
# mount could be done with just DEVICE or MOUNT_POINT if it has been defined in /etc/fstab
# mount -a # mount all devices defined in /etc/fstab
umount DEVICE or MOUNT_POINT # un-mount a partition from mount point
mount # shows any mounted device with mount options & filesystem
df -h # shows any mounted device with sizes
du -ah # show disk usages for files and directorys (-s switch show only totals)
cat /etc/fstab # auto mounting config file
Example :
# /dev/sda4 /media/mrht74/c auto defaults,rw,users 0 0
# the above line points that any user can mount
user management
# /etc/group # groups db
# groupname:x:gid:users joined this group
groupadd new
groupdel new
groupmod -g [gid] -n[name]
#groupmod -go [gid] -n[name] # overwrite gid
# ...............
# /etc/passwd # users db
# username:x:uid:primary_gid:details:$HOME_addr:shell_name
# we could disable user from logging in by setting shell_name to another program
useradd -m -s [shell_name] username # creates a new user
useradd username -g [pg_name] # adds user to group_name as primary group
# -m careates home dir for user , -s changes the shell , -G adds user to some other groups , -d chages home folder addr
# useradd config file at : /etc/default/useradd
gpasswd -a user_name group_name # adds user_name to group_name
# gpasswd used to administer /etc/group, and /etc/gshadow. Every group can have administrators, members and a password. -d deletes group from user Groups which memebered
groups user_name # returns groups user_name is memeb of them
usermod -l new_name # modify user name #
-L: Lock -U: unlock -d: chage home dir
userdel -r # delete user with its Home folder
# /etc/shadow # passwords db
# username:pass:
# pass field types:
# user:: # user without pass
# user:!: # disabled account
# user:*: # disabled account
# user:!_ENCRYPTED_PASS_: # dissable account temporary , it wil chage with usermod -L -U
# user:djnaskdbajdshbjasdh_ENCRYPTED_PASS_djhsbajhbdajdhbajd:
#
passwd user_name # change password for username
# IMPORTANT #
#└── sudo vs su direct acces , which one ? # at video
# └─────────────────────────────────────────────────
basic permission
# a file made up from user , group , acces , file
# access: owner+group+other # rw-rw---x = 661
# w acces to folder makes it possible to move and delete ist files
# each set :
# --- > 0
# --x > 1
# -w- > 2
# -wx > 3
# r-- > 4
# r-x > 5
# rw- > 6
# rwx > 7
chown newowner:newgroup filename # change file owner:group
chgrp newgroup filename # change file group
chmod 777 filename # change file access
chmod g-w filename
chmod [ugo][+-=][rwx] filename
# all of 3 commands above can be used with -R switch
stickyBit
# applies to folders only
# it can prevent delete, rename or move files in folder by useres with same group access
# /tmp is an example with 777 access and stickybit only
# 4 numbers on Access:
# 1 # --t = SUID + SGID + stickyBit
chmod +t file # adds stickyBit to file
# ➜ Desktop ls -l
# drwxr-xr-x 2 mrht74 mrht74 4096 Jan 22 17:25 new # folder access code : 755
# ➜ Desktop chmod +t new && ls -l # chmod 1755 new
# drwxr-xr-t 2 mrht74 mrht74 4096 Jan 22 17:25 new $ x changed to t
# ➜ Desktop chmod -x new && ls -l # chmod 1644 new
# drw-r--r-T 2 mrht74 mrht74 4096 Jan 22 17:25 new # x changed to T
# ➜ Desktop chmod -t new && ls -l # chmod 0644 new
# drw-r--r-- 2 mrht74 mrht74 4096 Jan 22 17:25 new # T changed to -
SUID
# applies to executable files
# if it SUID set, file will execute by its owner's permitions although run by any user
# /usr/bin/passwd is an example with (4755/-rwsr-xr-x) access
# 4 numbers on Access:
# 4 # s-- = SUID + SGID + stickyBit
# it goes on x place at ls -l , like above , nad switches between s and S if x or -
chmod u+s filename # adds SUID to file
SGID
# applies to exec files and folders
# on exec files SGID works like SUID and set runs exec file as its group access
# on folder if enabled, any files creates on this folder, gets group of folder (not file maker group)
# 4 numbers on Access:
# 2 # s-- = SUID + SGID + stickyBit
# it goes on x place at ls -l , like above , nad switches between s and S if x or -
chmod g+s filename # adds SGID to file
links
ln SOURCE DEST # crate link to first file inode on target
# this is hard link not working on directorys and cross partition
# single file with multi names (dir name + base name), takes unique Inode and disk space
# this is a link from name to Inode
ln -s SOURCE DST # crate symbolic link to first file inode on target
# this is symbolic link working on directorys and cross partition
# this is another file from source file , linked to source
# this is a link from name to another name
# -d switches make link to directories
compression & archiving
# gzip not working on pre-comprssed files preparely,
gzip filename # zip wiith d alg filename
# overwrites new file to old file
gzip -c[1-9] oldfilename > newfile.gz
# create zip on new file with power in 1-9
gzip -d filename.gz # unzip filename
bzip2 filename # zip with b alg filename
# better time and comppressing
# other cmmds like gzip
xz -c oldfilename > newfile # zip with b alg filename
# long time in compression and fast time in decompression
# Example:
# ➜ ls -lh
# -rwxr-xr-x 1 mrht74 mrht74 33M Jan 23 14:35 test.so
# ➜ time gzip -c test.so > test.so.gz
# gzip -c test.so > test.so.gz 3.51s user 0.03s system 99% cpu 3.538 total
# ➜ time bzip2 -c test.so > test.so.bz2
# bzip2 -c test.so > test.so.bz2 6.74s user 0.03s system 99% cpu 6.774 total
# ➜ time xz -c test.so > test.so.xz
# ls -lh
# xz -c test.so > test.so.xz 32.27s user 0.12s system 99% cpu 32.399 total
# ➜ ls -lh
# -rwxr-xr-x 1 mrht74 mrht74 33M Jan 23 14:35 test.so
# -rw-rw-r-- 1 mrht74 mrht74 11M Jan 23 14:39 test.so.bz2
# -rw-rw-r-- 1 mrht74 mrht74 12M Jan 23 14:38 test.so.gz
# -rw-rw-r-- 1 mrht74 mrht74 8.2M Jan 23 14:40 test.so.xz
tar -cvf OUTPUT_TAR_FILE # archive files to putput file
tar -cvzf OUTPUT_TAR_FILE # archive and compress using gzip files to putput file
tar -xf INPUT_TAR -C OUTPUT_DIR # extract archive to output dir
tar -xzf INPUT_TAR -C OUTPUT_DIR # extract compressed archive to output dir
# -z , -j , -J are switches for gzip, bz2 and xz for compression
# if set OUTPUT_DIR to / , then the files go to their default foldder
tar -tf INPUT_TAR # list archive content
tar -uf ARCHIVE_FILE OTHER_FILES # update existing archive with new files
find /etc/apache2 | cpio -o > OUTPUT # creates cpio file
cpio -di < INPUT_FILE # extracts cpio file
# if input files when archiving has relative addresses , then extracting will be relative
rar x FILE.rar # extract file in current directory
rar x tecmint.rar /des/dir # extract file in dest directory
rar a OUT.rar SOURCE # create archive from source on out
# switches: -hp set password for names and content with prompt
# -p set password for content with prompt
# -rr[N] set recovery level
# -v<size>[k|b|f]Create volumes with size=<size>*1000 [*1024, *1]
proccess
# any proccess made of PID, PPID, Prioty, Owner (user or UID), state, pmem, pcpu,
ps # shows proccesses on current shell
ps -e # shows entire system proccesses
ps aux # BSD switches, shows another list of details
# ps -f # shows more details
# ps -l # shows long list
# ps -H # shows as tree
# ps -eo pid,ppid,uid,user,pcpu,pmem,state,stat,cmd,comm,priority,psr,f,fname,stime,etime,mlwp
# above cmd formats output result
# proccess states: S, R, T, Z,
pstree # shows ps tree
pgrep -a PS_NAME # finds proccess PID
pidof
kill -SIG PID # send signal SIG to ps
pkill PS_NAME # kill prossess name
# any signals could bee handled bye programm , but SIGKILL ( -9 ) could not be hanled
# some signals :
# INT = ctrl+C = -2 , TERM = -15 , KILL = -9 , STOP = -19 , CONT = 18
killall PS_NAME # kill all ps named PS_NAME
pkill PS_NAME # kill ps named PS_NAME
# prioty is in 0-39
# default is 20
# just root can run a ps with priority lower than 20
nice -n+19 cmd # runs CMD with 39 priority code
# nice number is in -20,+19 equal to 0,39
renice -n PRI_NUM -p PID -u USER # change a ps priority
top # intractive ps manager
htop # intractive ps manager
CMD & # send cmd to background
jobs # show active jobs
fg JOB_ID # come JOB_ID to foregrounds
ctrl + Z # stops current ps and sends it to bg
bg JOB_ID # cantinue a bg ps
uptime # to view load average and uptime
w # show who is online with load averige
watch -n1 CMD # runs a cmd periodic
free -m # RAM status
swapon -s # swap summery
# /proc/cpuinfo is cpu status file
screen -S SCR_NAME # create a screen
ctrl A+D # deatach from a screen
screen -r SCR_NAME # return to screen
nohup CMD # runs cmd under init ps
# not advised to use nohup
packages
# RedHat based packages are .rpm files and Debian based packages are .deb files
# Alien converts this packages together
# package naming pattern: package_name-version-release-cpu_arch
rpm -i PACKAGE_NAME # install package on rpm based system
rpm -qa # query all installed packages
rpm -ql PACKAGE_NAME # list all files of PACKAGE_NAME
rpm -qi PACKAGE_NAME # view information of PACKAGE_NAME
rpm -qR PACKAGE_NAME # view requirements of PACKAGE_NAME
#any of above query commands could run on .rpm file with switch -p
rpm -q --whatrequires PACKAGE_NAME # view which packages requires PACKAGE_NAME to work
rpm -e PACKAGE_NAME # removes PACKAGE_NAME
rpm -qf FILE_NAME # finds parent package of a single file
rpm2cpio # converts rpm to cpio
dpkg -i PACKAGE_NAME # install package on debian based system
dpkg -P PACKAGE_NAME # removes PACKAGE_NAME and its config files
dpkg -r PACKAGE_NAME # just removes PACKAGE_NAME
dpkg -L PACKAGE_NAME # view all files of a PACKAGE_NAME
dpkg -l PACKAGE_NAME # ensure a PACKAGE_NAME is installed or not
dpkg -s PACKAGE_NAME # view information of PACKAGE_NAME
dpkg -i PACKAGE_FILE # view information of PACKAGE_FILE
dpkg -c PACKAGE_FILE # view all files of a PACKAGE_FILE
dpkg -S FILE_NAME # searchs parent package of a single file
dpkg -X PACKAGE_FILE OUTPUT # extract dpkg file
# repositories are set in /etc/apt/sources.list
apt update # updates apt cache
apt install PACKAGE_NAME # install a package
apt-get clean # deletes downloaded .deb archive folder
# downloaded .deb archives in /var/cache/apt/archives
apt-get clean # deletes downloaded .deb archive folder
apt autoremove # autoremoves unneccesary packages installed
apt upgrade # update all packages
apt-mark hold PACKAGE_NAME # prevent PACKAGE_NAME from updatingsssssssssssssssssss
# other commands are: unhold, showhold
apt search KEY # search on apt local cache for KEY
apt show PACKAGE_NAME # shows more infor about pckage
apt-cache depends PACKAGE_NAME # shows dependencys of a PACKAGE_NAME
apt-cache rdepends PACKAGE_NAME # shows packages depends to PACKAGE_NAME
# yum config file in /etc/yum.conf
# yum repos are in /etc/yum.repo.d/*.repo
yum install PACKAGE_NAME # install a package
yum remove PACKAGE_NAME # don't use # remove package and any pckage depends to PACKAGE_NAME
yum upgrade # upgrade all of your packages
yum clean packages # deletes downloaded .rpm archive folder
# by default is in /var/cache/yum
yum search KEY # search on yum local cache for KEY
yum list {all,available} # lists {all,not-installed} packages
yum info PACKAGE_NAME # shows more infor about pckage
# IMPORTANT #
# └── yum config file edit # at video
# └────────────────────────────────
vim skill
basics
# by default in command mode
# i insert mode
# v visual mode
# a append mode (insert after curser)
# A append mode at end of line (shift + a)
# o open new blank line below curser and switch to insert mode
# O open new blank line above curser and switch to insert mode (shift + o)
# :q! quite without save
# :wq save and exit
# :x save and exit
# ZZ save and exit (shift + z + z)
# :w save
# :wq FILE_NAME saves as new file
# ctrl + g print current file status and curser location
# :f print current file status and curser location
# :! CMD execute externam terminal command CMD
# :r FILENAME retrieves disk file FILENAME and puts it below the cursor position
# :r !CMD reads the output of the command and puts it below the cursor position
# :syntax off turn off syntax highlighting
# :set nu show line numbers (:set nonu to hide line numbers)
movement
# Typing a number before a motion repeats it that many times example: 2w, 3e,
# h,j,k,l to move curser by char
# w,b,e to move curser by word
# % jump to matching (,{,[ or ],},)
# (also can use W,B,E which jump only on spaces, not _ , - )
# :LINE_NO jumps to line number
# 0 jumps at start of of line = home
# $ jumps to end of line = end
# G jump to last line (shift + g)
# gg jump to first line
# ctrl + f page down
# ctrl + b page up
delete text
# x delete char under curser like Delete key
# X delete char before curser like back space (shift + x)
# dw delete word from curser until next word
# de delete word from curser until last char of current word
# D white the line from curser to end of line (shift + d)
# dd delete current line
# Number + dd delete some lines from current line to down count number
# dG deletes entire lines below (d + shift+g)
replace text
# r + New_char replace current char with new_char
# cw delete current word and go to insert mode
# R switch to replace mode (shft + r), replace inserted char until esc
history
# u undo one step (:undo)
# U undo total chages of current line (shift + u)
# ctrl + r redo one step (:redo)
copy, paste
# yy copy current line
# yw copy one word,
# Number + yw copy Number of words (also can press y+Number+w)
# Number + yy copy number of lines below curent curser
# p paste after current line
# P paste befor current line (shift + p)
visual mode
# all movement keys also work in this mode
# v switch to visual mode
# y copy selected text
# d copy and delete selected text (cut)
# :w after selecting press :w FILENAME to save selected part as new FILENAME
search and replace
# /WORD search forward
# ?WORD search backward
# / + enter jump to next word found (also can press n)
# ? + enter jump to previous found (also can press N)
# :s/old/new/g to substitute 'new' for 'old' in current line (delete g to apply for first word found)
# :#,#s/old/new/g #,# are the range of lines where the substitution is to be done.
# :%s/old/new/g to change every occurrence in the whole file.
# :%s/old/new/gc to find every occurrence in the whole file, with a prompt to substitute or not
# :set xxx sets the option "xxx". Some options are:
# 'ic' 'ignorecase' ignore upper/lower case when searching
# 'is' 'incsearch' show partial matches for a search phrase
# 'hls' 'hlsearch' highlight all matching phrases
# 'no+xxx' disables xxx option
hardware and network
dig DOMAIN # get DNS info for domain
dig -x host # reverse lookup host
host google.com # lookup DNS ip address for name
sudo netstat -tulpn # view open ports in ubuntu
sudo netstat -ntlp # like above
sudo netstat -vatn # like above
sudo ufw allow 6880 # open a port
dmesg # dmesg is used to examine or control the kernel ring buffe
cat /proc/cpuinfo # display cpu info
cat /proc/meminfo # display memory info
cat /proc/interrupts # show interrupts per cpu per I/O
free -t # show free and used memory (-m, -g, -mega, --giga, --si ,-t)
lshw # display info about hardware configurations
lsblk # show block device related info in linux
lspci # list all pci slotss (-t -v, -k, -vv, -vvv )
lsusb # list all usb slots (-t -v)
lshw -class network # list all network hardwares
lsmod # view which modules loaded on kernel
modinfo MODULE_NAME # Show information about a Linux Kernel module
dmidecode # show hardware info from the BIOS
hdparm # get/set SATA/IDE device parameters
# Example :
hdparm -i /dev/sda # show info about sda
hdparm -tT /dev/sda # read speed test on sda
ifconfig -a # list all network interfaces
# Examples:
# ifconfig eth0 up [or down]
# ifconfig eth0 192.168.1.100/24 up
ethtool eth0 # view [and edit] network interfaces properties of eth0 interface
# -i shows driver info, -S shows statistics, -p blink network card light
# -s change settings (see man ethtool)
# Example: ethtool -s eth0 speed 100 duplex full autoneg off
ip # main network tools alternative to ifconfig
# Examples:
ip link show # show interfaces
ip link show dev eth0 # show interface eth0
ip link set down dev eth0 # set down eth0
ip addr show dev eth0 # show ip address of eth0
ip addr flush dev eth0 # clear ips of eth0
ip addr add 192.168.1.100/255.255.255.0 dev eth0 # add ip to eth0
ip addr add 192.168.1.101/24 dev eth0 # add ip to eth0
ip addr del 192.168.1.101/24 dev eth0 # delete ip from eth0
# if primary ip got deleted , all secondary ips will delete too
# but secondary ips could be deleted one by one
# ifconfig only shows primary ip address, but ip shows all
# ip supports shortened commands like ro=route, sh=show, del=delete, ...
ip route show # shows routing table
route -n # shows routing table
ip route add 8.0.0.0/8 via 10.1.1.201
ip route add 0.0.0.0/0 via 192.168.1.1 # set default gateway
ip ro add default via 192.168.1.1 # set default gateway
ip ro del 8.0.0.0/8 # delete route
# if main route got deleted, althogh existance of ip and link UP, but can not ping anyone
# DNS is in /etc/resolv.conf
nslookup # obtain an domain ip from DNS servers in /etc/resolv.conf
host # obtain an domain ip from DNS servers in /etc/resolv.conf
dhclient -v # set network config by DHCP
ifup eth0 # up a network interface with default config in /etc/network/interfaces
# Debian network script
# permanent ip configs stored on /etc/network/interfaces
# this file used on ifup eth0
# Example:
# auto eth0 # this line must add to enable this config on boot
# iface eth0 inet static
# address 192.168.1.20/24
# gateway 192.168.1.1
# dns-nameservers 4.2.2.4
# up CMD # run CMD when this interface get UP
# down CMD # run CMD when this interface come DOWN
# or we can use DHCP
# face eth0 inet dhcp
# RedHat network script
# permanent ip configs stored on /etc/sysconfig/network-scripts/ folder
# there is ifcfg-* files for each interface
# on boot any file starting with ifcfg- in this folder loaded, names not important
# Example:
# DEVICE=eth0
# HWADDR=00:00:00:ff:ff:ff
# TYPE=Ethernet
# UUID=xxxxxxxxxxx
# ONBOOT=yes # equels to auto eth0 on Debian
# BOOTPROTO=dhcp
#--or we can use static
# BOOTPROTO=none
# IPADDR=192.168.4.37
# PREFIX=24 # or we can use NETMASK=255.255.255.0
# GATEWAY=192.168.4.1
# DNS1=8.8.4.4
# DNS2=4.2.2.4
# NM_CONTROLLED=yes
boot loader
# Firmware -#> MBR at boot (Master Boot Record )
# Sector 0 - first 512 bytes of Hard Disk , contains boot loader + PT + Reserved
# 446 bytes -#> code , 64 bytes -#> PT (Partition Table) , 2 bytes -#> Reserved
# boot loaders programs :
# LILO (Linux Loader)
# GRUB Legacy
# GRUB2
#
# boot loader should : (LILO work like this)
# 1.know partitions
# 2.know filesystems (ext4)
# 3.Load kernel
#
# GRUB work like this : GRUB stage 1, GRUB stage 2
# 1.know partitions
# 2.know filesystems (ext4)
# 3.Load Grub stage 2
#
# grub has features like: password, iso file OS load, dual boot support, ...
# EFI
# EFI has native boot manager can load other boot loaders
# EFI allow you to select a boot loader to run after boot
# EFI installed on first sector (boot sector) of a partition (not entire Hard)
# EFI -#> ESP (EFI System Partition) -#> mount /boot/efi/.../... .efi
# on grub menu:
# press e to edit grub options
# press c to open grub shell
# we can use grub shell to load linux kernel manualy
# we should go and find kernel
# kernel usualy located on /boot/kernel* or /boot/vmlinuz*
# kernel has some parameters on load
#
#
# grub shell commands
ls # list hard disks and partitions
ls (hd0,1)/ # list (hd0,1) partition files
set root =(hd0,1) # by setting this next time we can use ls /
ls -l /boot # list boot partition to find kernel
linux /boot/vmlinuz* root=/dev/sda1 # load kernel and add root parameter
linux /boot/vmlinuz* root=/dev/sda1 ro # loads kernel read only (security option)
initrd /boot/initrd.img* # load kernel loading dependencies like ext4,...
boot # start booting
linux startup
# Firmware -#> boot loader -#> kernel -#> initialization process (init)
# initialization process programs:
# systemV (sysV) , system-d, ...
# /sbin/init is first and only program runs by kernel with PID=1 with a runlevel
# /etc/rc[0-5].d files are runlevel config files used by init
# runs any script file on /etc/rc2.d/* (these files linked to a script on /etc/init.d/FILE)
# scripts with name starting with s* , runs by "start" parameter
# scripts with name starting with k* , runs by "stop" parameter
runlevel # prints current runlevel
# runlevels 0,1,6 are predefined on different distros, runlevel descriptions are:
# 0 shutdown -any distro
# 1 Single, S, s, Single User Mode -any distro # only root login without pass for troubleshooting
# 2
# 3 -RedHat based uses this GUI not loaded
# 4
# 5 -RedHat based uses this GUI
# 6 reboot -any distro
#
# Debian based not use runlevels
#
# on Debian based we can use:
update-rc.d # manage runlevels configs
# on RedHat based we can use:
chkconfig # manage runlevels configs
chkconfig --list sshd # shows sshd services status on each runlevel
chkconfig --level 34 sshd off # turn off ssh on runlevels 3 and 4
graphical enviroment
# X-Server : controls input and output (display, mouse, keyboard) work on TCP
# before 2004 linux used X-free 86
# now using X-org
# any graphical app connects to x-server and uses x-libs
# we name any app connects to x-server as x-client
# we use widget library codes and widgets connect to x11 lib
# @ using widget has feateres : 1) coding easier, uniform applications
# widgets like gtk+, Qt, Motif, Xaw, ...
#
# window manager is only service connected to x-server
# other applications using window manager
# window manager can handle multiple app windowses
# popular window managers: Metacity, Compiz, kvin, kwm, sawfish
#
# Graphical Login (Display Manager)
# runs before any process,
# it uses pure x-server to display login
# it runs x-server, then window manager
# popular display managers: lightdm, gdm, kdm, ....
#
# to make these steps easier , some projects like gnome, kde, unity, xfce, lxde, mate, ... started
# they install x-server, widgets, display manager, window manager,
# we call these projects Desktop Enviroment (DE)
# gnome, kde, unity are large and high weight
# xfce and lxde are light weight
window & desktop sharing
echo $DISPLAY # returns display ip and number, default is 127.0.0.1:0
# by changing this var to another ip we can share applications windows on another machine
export DISPLAY=192.168.1.3:0.0 # set destination system to display home system windows
# now we should set destination machine
# we should change display manager config of destination
# on ubuntu
vim /etc/lightdm/lightdm.conf.d/my.conf
# should edit like this
# [SeatDefaults]
# xserver-allow-tcp=true
# now shuld restart lightdm service
service lightdm restart # restart window manager to take effect accepting external windows to display
# now we should set access control list of destination system's xserver
xhost +192.168.1.2 # add ip to allowed source for display wndows
xhost + # allow any ip
# we can use xserver on Microsoft Windows using Xming
# above method is NOT secured
# the secured method is:
ssh -X user@server-ip # ssh to server allowing xserver forwarding
# xserver forwarding should be enabled on server like this:
# edit /etc/ssh/sshd_config and set X11Forwarding yes and restart ssh service
# on RedHat we can restart ssh like this
# systemctl restart sshd.service
#
#
# --- total desktop sharing
#
# we can use remote desktop with XDMCP by editing display manager config
# in ubuntuwe can edit /etc/lightdm/lightdm.conf.d/my.conf
# [SeatDefaults]
# xserver-allow-tcp=true
# [XDMCPServer]
# enable=true
# now we configed server
# now restart lightdm service #service lightdm restart
# on RedHat based client we should install:
yum install xorg-x11-Xephyr
# on Debian based client we should install:
apt install xserver-xephyr
# then we could user this command
Xephyr -ac -query 192.168.1.2 -br -reset -terminate :2
logging
# each log has a facility
# popular facilities: cron, kern, mail, news, syslog, local [0-7],
# each log has a priority
# priority levels: debug, info, notice, warning, err, crit, alert, emerg
# log has selectors contains facility.priority
# mail.err /dest/to/file # log mail err and above err messages on DEST
# mail.!err DEST # log mail err and below err messages on DEST
# mail=err @10.1.1.1 # log only mail err messages on 10.1.1.1 ip
# kern.emerg * # send message to any user logged in
# /etc/rsyslog.conf is rsyslog config file
# /etc/rsyslog.d/50-default.conf also included
logger -p kern.emerg 'OOrjansi Residegi KON ' # can send logs for test and for send log on our scripts
# we store security logs on another machine named rsysog server
# we should enable TCP and UDP syslog reception on rsyslog server
dmesg # all the messages from the kernel’s buffer
impoetant logs:
regex
# regex engines may be different
# we read pattern char by char
# regex is case sensitive by default
# dash (-) has meaning only at bracket [character class] like [0-9]
# we use \ to use literal meaning of metacharacters
# we should usualy place pattern in ""
# [] means character class, it mean only one char equel on of char inside it
# {k} refers to previous char, means k repeat of prev char
# {n,m} refers prev char should repeat between m and n times
# {,3} and {4,} are valid , setting only min or max repeat times
# ^ means start with
# $ means wnd to
# * equels to {0,}
# + equels to {1,}
# ? equels to {0,1}
# [^SOME_THING] means not having SOME_THING # ^ in the [] means NOT
# \d means [0-9] (not work in bash )
# | means or
# ( uses for sub pattern)
grep -E # grep with extended regex
egrep # grep with extended regex
egrep ^s # grep string starting with s
egrep d$ # grep string ending to d
egrep ^.$ # grep string any SINGLE char
egrep ^F.$ # any dual char string with first char = F
egrep ^F[0123456789]$ # match only with F1,F2,F3,...F9,F0
egrep "^F[0-9]$" # match only with F1,F2,F3,...F9,F0
egrep "^[FX][0-9]{4}$" # any string starting with F or X, with 4 numbers afer that
egrep "^aaa$" = "^a{3}$" # these are equal
egrep "^z{2,5}$" # matchs to zz or zzzz or zzzz or zzzzz
egrep "^5a*5$" # matches to 55, 5a5, 5aa5, 5aaa5, ...
egrep "^5a+5$" # matches to 5a5, 5aa5, 5aaa5, 5aaaa5, ...
egrep "^5a?5$" # matches to 55 and 5a5
egrep "^a[^0-9]*a$" # matches with aa, a[anything is not char]*a
egrep "^(ahmad|nima)$" # matches only to nima or ahmad
egrep "^(s[0-9]{2}|xff)[0-9]{4}$" # matches with s###### or xff#### (# means a number)
# in find command , it has ^ and $ by default
# Example:
find . -regex ".*ser.*" # it finds file named insert.py
cron
# it automaticly do something
crontab -e # to edit cron file
# crontab -r # clears the crontab file -#> WARNING!
# cron files stored in /var/spool/cron/crontabs
# each line in this file is for one schedule
# each schedule has 6 parameters seprated by white space
# a cron task syntax like this :
# * * * * * mkdir /home/mrht74/Desktop/AAA # executes every minute
# Minute Hour Day Monthr WeekDay Command
# columns be anded together
# each column number refers to number of that fied
# we can use , in each columnt to use multiple values (usualy use this)
# we can use */10 to set periodic time
# Example:
# 5 6 * * * ls # ls every day on 06:05
# * 8 * * * ls # ls every minute from 08:00 to 06:59 every day
# 0,30 7 * * tue ls # every week on tuesday at 07:00 and 07:30
# */10 4 * * * ls # runs at 4:00, 4:10, 4:20, 4:30, 4:40, 4:50
# $PATH variable value is different from local in cron jobs
# in cron path is $PATH=/usr/bin:/bin
# we have 2 solutions:
# 1) copy user PATCH at begining of script
# 2) use complete command names like /sbin/iptables
# we have some folders in /etc/cron.*
# cron.daily/ cron.hourly/ cron.monthly/ cron.weekly/
# which are for packages automatic jobs
# we can not use interactive scripts on cron
mysql database
mysql basics
# we can use mariadb-server alternative to mysql
service mysql start # start mysql service (start/stop/restart/status)
mysql -u root -p # open mysql as root and prompt for pasword
mysql -u root -pPASS # open mysql as root and PASS
mysql_secure_installation # some step by step prompts to secure mysql
# we can run sql script like this:
cat script.sql | mysql TABLE_NAME -u root -pPASS -t # -t draws tables on stdout
mysql TABLE_NAME -u root -pPASS -t < script.sql
some mysql shell commands
-- this is a comment
SHOW DATABASES;
-- commands are case sensitive but we type upper case
CREATE DATABASE test;
-- DB name is case sensitive on GNU/Linux and solaris and BSD (not MS Windows)
USE school
-- WARNING! we shouldn't place USE on sql scripts, we should send db name as
-- mysql command parameter
SHOW TABLES
DROP TABLE IF EXISTS students
-- CRUD commands are: create, select, update, delete
CREATE TABLE students
(
ID INT AUTO_INCREMENT PRIMARY KEY,
FN TEXT,
LN TEXT,
GENDER ENUM('F','M'),
SCORE INT
);
DESCRIBE students
-- draw table structre
INSERT INTO students (FN,LN,GENDER,SCORE) VALUES ('Ali','Sadeghi','M',90)
INSERT INTO students (FN,LN,GENDER,SCORE) VALUES ('Azar','Hosseini','F',95)
SELECT * FROM students
SELECT FN,LN FROM students;
SELECT CONCAT( IF(GENDER='F','Ms. ','Mr. ') , FN,' ',LN) AS FULL_NAME , SCORE
FROM students
UPDATE students SET SCORE=94 WHERE ID = 2
DELETE FROM students WHERE ID = 1
mysql backup and restore
# we can create backup of a database like this:
mysqldump -u root -pPASS school_db > ~/Backups/school_sql_backup.sql
# we can restore like this
mysql resotre_db -u root -pPASS < ~/Backups/school_sql_backup.sql
utility
sudo apt install moc
mocp
sudo apt install links
links digikala.com
eog path/to/picture
sudo apt install mplayer
sudo apt install finger
finger USER
fun commands
figlet "something" # word art "something"
figlet `COMMAND` # word art result of COMMAND
echo "1234" | rev # reverse string
tac # like cat but from botton to top
sl # animation
yes WORD
factor NUMBER
lolcat
cmatric
toilet
echo "SALAM" | toilet | lolcat