Linux - 2

First check whether you are root user or just a user.

If you are user, than follow the commands

[User..........~]$ sudo su

[root........user]# cd

[root.......~] to change to different user than

[ root...~] cd /home/ec2-user/

[root.....user].. Now execute all commands

Command	Description	commands

cd	change directory.	`cd`
cd - or cd ..	moves to the previous directory.	`cd - or cd ..`
cd ~	takes you back to the home directory.	`cd ~`

ls	list directory contents.	`ls`
ls -a	lists all the files including hidden files.
ls -x	lists the content in row-wise format.
ls -r	lists the contents sorted in reverse alphabetical order.
ls -t	lists the directory contents sorted by last creation time.
ls -s	to list the file size
ls -R	lists all subdirectories under a current directory.
ls -l	displays all files & directories in long format.
ls -u	lists the contents based on access time or usage time.
ls -A	list almost all include hidden files . except . and ..
ls -F	to display all the file by type dir file _ / executable file _ \ , link file* _ @
ls -f	to disable colors
ls [abc]*	lists all the files starting with the letter a/b/c.
ls [!abc]*	lists all the files that don't start with the letter a/b/c.
ls /	root directory contents will be displayed.
ls ../	displays the content of the parent directory.
*ls /**	lists the contents of all subdirectories of the current directory.
ls -d*	displays all directories followed by filenames.

touch	creates an empty file. or change the time stamp	`touch filename`
touch -a	changes the access time of a file.
touch -m	changes the modification time of a file.

moving & renaming
mv	used to move or rename files and directories.	mv oldname newname
mv -f	forces overwriting of the target file.
mv -i	prompts before overwriting the destination file.
mv -p	preserves the attributes from 1 file to another file.

rm	removing or deleting 1 or more files.	`rm filename`
rm -i	prompts before deleting each file. i means intimate
rm -r	recursively delete a directory and all its contents.
rm -rf	to remove file or dir with forcefully without get any error
rmdir	to remove the directory only
rm -rv	to know the sequence of deleting file or dir

uname	shows the name and certain features of the system.
uname -r	displays OS release details.
uname -m	displays machine details.
uname -v	displays version details.

cp -i ,-v	copy file or a group of files across directories.	`cp sourcefile destinationfile`
	copy all files of dir1 will be copied in dir2	`cp dir1/* dir2`

pwd	prints current working directory.
mkdir	to make directory


rmdir	removes the directory.
echo	displays messages.
cat	used to concatenate and display files.	-n(num),-b(blank)
	to create a file	`cat > filename`
	to view file	`cat < file name` or `cat file name`
	to append the data in a existing file	`cat > file name`
whoami	gives self-login details.
sudo	lets us use our account and password to execute system commands with root privileges.
tree	to list the content of directories and files in tree format

if we want to create a directory within directory at once then -

mkdir –p DevOps/Linux/ShellScriptin/Git/Maven/Tomcat
use this when you write custom permission - mkdir –m 700 python(with the file permission)

Inode : Inode is a Data Structure, stores the file/dir info

*chmod(symbolic codes)*
`u /g /o /a users/group/others/all`	`r / w / x (read/write/execute)`	`+ / - / = add/remove/assign`	change the access permissions on a file.
`chmod u/g/o/a file.txt`		`chmod u/g/o/a+r file.txt`	added read permission to file.txt
		`chmod u/g/o/a+w file.txt`	added write permission to file.txt
		`chmod u/g/o/a+x file.txt`	added execute permission to file.txt.
		`chmod u/g/o/a+rwx file.txt`	added all permissions at once to file.txt

*chmod (numeric, octal representation)*
Octal numbers	Binary value & text equivalent	Example	Description

	binary equivalent (r,w,x) for (owner, group, and others)
0	000 _	`chmod 000 file.txt`	all types of access are denied.
1	001 x	`chmod 111 file.txt`	execute access is allowed to u+g+o.
2	010 w	`chmod 222 file.txt`	write access is allowed to u+g+o.
3	011 _ w x	`chmod 333 file.txt`	write and execute access is allowed to u+g+o.
4	100 r	`chmod 444 file.txt`	read access is allowed to u+g+o.
5	101 r _ x	`chmod 555 file.txt`	read & execute access is allowed to u+g+o.
6	110 r w _	`chmod 666 file.txt`	read & write access is allowed to u+g+o.
7	111 r w x	`chmod 777 file.txt`	all types of access are allowed to u+g+o.

Some Other examples
command	Description	Command	Description


*chgrp*	to change group name	`chgrp demo.txt root`	domo.txt belongs to root group
chown	to change owner	`chown root demo.txt`	now owner of demo.txt is root

_ if in case it shows username or group name is invalid then add sudo adduser <name>

umask :

Means user mask. hiding permissions

It is going to set default permissions to file/directory

first is sticky bit mostly used in admin related activities

Linux - 2

Basic Linux commands & file Permissions

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