Linux/Linux Commands.txt at master · carlesgl81/Linux · GitHub

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Linux Commands

ls -> list files and folders
	ls -alh -> shows all properties
touch -> creates a file
cat -> shows text files content in terminal
mkdir -> creates a folder
rm -> remove a file
rmdir -> remove a folder
rm -r foldername/ <- if the folder is not empty
man -> help
	man mv
	man mkdir
	etc...
cd -> cd FolderName/
      cd ../.. para ir al root
cp -> copy file to somewhere cp foldername/test.txt testcopy.txt

Text Editors

Easy: Nano
Best to learn: vi   (man vi)
for Programming: emacs

mv test.txt renametest.txt -> renames a file

Pipes
	Standard In -> 0
	Standard Out -> 1
	Standard Error -> 2

0,1,2 are file redirectors.

xxx >sometext.txt -> Add a result to a file. Overwrite if something written.
xxx >>sometext.txt -> Append the result to the file content. Do not overwrite.

mail -s "this is the subject" carles < message.txt

ps -> shows processes
ps aux | less

Ctrl + r -> reverse commands: para buscar antiguos comandos usados en la
	sesión y buscar por nombre si hace falta

ln -s file3 file3LINK -> acceso directo / link a ese archivo.

head -> shows the first 10 lines of the file
tale -> shows the last 10 lines of the file

shutdown -h now -> apaga el sistema
init 0 -> apaga también
poweroff

sudo to start root

in CentOS/RHat/Suse/Fedora/MacOS use yum to install packages
in Ubuntu/Devian use apt-get to install packages

su to access to root, then yum update -y kernel. Then, sudo yum update.
sudo yum upgrade

sudo yum install firefox
sudo yum uninstall firefox
yum-cache search WHATEVER -> to find any software in your computer

To install GUI in CentOS

- dnf group list
- dnf groupinstall workstation
- To start with GNOME directly always: systemctl set-default graphical.target
- systemctl isolate graphical.target -> to start graphical mode from terminal


Top -> shows processids (PIDs)
htop -> https://www.cyberciti.biz/faq/how-to-install-htop-on-centos-linux-8/

Init 1 -> is the first process.
ps aux | grep init -> looks for init processes.

Effective user ID -> user id process.

Signals -> how processes communicate between them.

Kill (9 SIGKILL)-> closes a process "Kill 4833" Only if a process is not responding.
Kill (15 - SIGTERM) -> to terminate a process in a nicer way.
cups -> allows you to print on network printers.
sudo killall cups -> this would kill all processes of cups
sudo pkill -u carles -> would kill all processes for my user
man pkill
man 7 signal

Monitoring
process states
	1 RUNABLE (will be scheduled to use the CPU)
	2 SLEEPING (waiting to use the kernel/cpu)
	3 ZOMBIE (finished to use the cpu, waiting to return the result, then will be killed)
	4 STOPPED (paused, stopped. Waiting to continue what it was doing)

Niceness -> priority between processes. Higher number, nicer is a process to another processes
	in relation to other processes. Higher the number, lower the priority.
nice -n 15 /backup/not/important/at/all/task
sudo renice -5 2744 -> to renice a process.
With htop we can change the priority with F7 and F8.

priority goes from -20 to 20

proc -> file system (kernel posts the currently running processes)
ls -alh /proc -> show the processes in proc.
ls -alh /proc/PIDNumber -> shows the

sudo -i -> sudo interactive bash session.

strace ->find out what processes are doing.

Linux File System
	etc/ configuration for data and applications. You start here with troubleshooting.
	sbin/ secure binaries
	bin/ binaries
	tmp/ temporary files
	lib/ (dll in windows)
	lib64/
	media/ auto mount devices (ubuntu)
	mnt/mount
	opt/ optional software
	proc/ configuration files of processes running.


man hier - find help for these folders and structure.

Linux Layout
	sda -> disk
	sda1 -> partition

ifconfig -> shows physical and virtual networks

/usr/share -> stuff that may be common to many systems. Like to create images for desktops
/var/log -> system logs

netstat -tupln
sudo netstat -tupln

scripting
	&& - do_something && if it ran succesfully, do_something_else.
	If program 1 works, program 2 will run.
	If program 1 does not work (error), program 2 won´t run.

cut -> man cut
sort -> man sort
wc -> man wc

grep -> searching tool
cat file.txt | grep user
	user:love
grep someone file.txt
uniq