Linux
Open source
Security
All devops tools can run
Distribution / flavours of linux
Red hat linux (7.x, 8.x) - enter edition / using for technical support /
all software - pay
Centos linux (7.x, 8.x) - without any technical support utsing - not pay
Ubuntu (22.x)
Open suse (14.x)
Fedora
Debian
etc
Linux OS terminology
Hardware
Kernal (2.x = 6.x, 3.x = 7.x, 4.x = 8.x, 5.x = 9.x)- intermidiate of shell and
hardware / the kernal exacute the command / it performs all the task /
every task such as ls, hostname, mkdir, etc…
Grub2 - grant unified boor loader 2 (it booting kernal)
Shell (#- admin (root), $- non admin/limited access (user id) - using run
the command
Commands
Physical server - directly install
One hardware
One OS
Virual server
Multiple server
Usinbg hypervisor software (types => esx -I = VM ware, xen = citrix(open
source), hyber -v = MS
Single hardware multiple OS
Command for seeing kernal version # uname -r
Directory - structure
Main drive is # /
Boot - booting files
Root - cd /root (only admin can access)
Home - cd /home/raju (every user home directory)
Etc - all system configuration
Dev - hard disk list (storage)
Var- variable directory (system logs)
Bin - command location / binary / which ls (normal user)
Sbin - super user binary / which fdisk
Tmp - temporary directory (important directory linux)
Ram checking # free -h
Hard disk # lsblk
Cpu checking # lscpu
Can view all using command # history
Os version # cat /etc/os-release
# date & time = use normally can view
Calander # cal
Mention year # cal 2023
Every login user send the notification # wall “im going to shutdown”
Showing ip address # hostname / if config / ip a
/ main directory
Change directory # cd /
List under current folder # ls
Detail of the folder # ls -l
dr-xr-xr-xr-xr - should be 10 digit (first one -(directory) / next two (user) /
next two (group) / next two (others)
lr-xr-xr-r
-x-xr-ex-r
Start with “d” its directory (sans)
Start with “l” its link file (sans -> xxx,xxx)
Start with “-” its file
Last modify time # ls -lt
Last reverage # ls -ltr
# useradd name
Set up password # echo “redhat” | passwd --stdin user name
User connect or not # w
User connection checking # pikill -9 -t pts/o
Add every user name like this then w using view connection
# walch -n 1 w
Kick out user # pkill -9 -t pts/o
Root # whoami
Root /time/date/terminal type/ip # who am i
view login user # w
Stop viewing # watch -n 1 w
Path # cd /tmp
Delete old files # rm -rf *
Home path # pwd
Give # w
Give # 11
Display file content # cat filename
Find and replace the file # :%s/find/replace/g
Line number # :set nu
Remove number # :set nonu
# cat -n filename (can check home many lines)
Last line # tail filename # tail -3 filename
First line # head filename
Line by line # less filename
Percent of file # more filename
Fine the word in file # grep word filename
All file search # grep word *
File searching upper or lower # grep -i word filename
Where the first word started line # grep -i ^word filename
First word # grep ^word sandy
Except this all # grep -v ^word sandy
Filter command
# cat -n filename | head -100
# cat -n filename | head -100 | tail -11
# ip a | grep inet
# ip a | grep inet | grep -v inet6
Directory command
# mkdir
Showing all latest time creating file # ls -ltr
Remove directory # rm -rf directory name
# ls -l direc name
# cp filename direc name
# cp * dir name/
# man cp (can clarrify all the meaning)
# mkdir /opt/directory name = ex mkdir /opt/backup (creating dir in opt
path)
# cp -R dir_name /opt/backup
