Shell-Commands-part5

File permissions in Linux:Each file or directory in linux is assigned with three types of owner i.e User,Group and others.
Linux file ownership:
USer -- User is owner of file ,By default who created the file is the onwer of file
group: Group is defined as collection of users having the same permission . If you have a group of users from development team and want them to give same set
of permissions for a file , then you can define permissions at group level and all the users inside that group will have same access.
others: Other means access to the rest of world who is neither the owner or belong to any group.

Linux file permissions:
read : Permission to open and read a file .
write : Permission to modify the content of file.
execute : Execute permission means to run that command such as running .exe file for windows or .py for python code .

To view the permission of file/dir assigned to the user,group or others run the command : ls -l
Lets say you get output as -rw-r--r--  SA-sample.yaml.
below is the detail of each character in -rw-r--r-- 
- ===>It shows that the output is of file type .If its d then directory type.
rw- ==> The first three character belongs to user means user has read and write access to the file . Execute is - means no execute permission on file.
r--  ===> The next three character belongs to the group .Means the user assigned to the group will have only read access to the file .
r--   ==> The next three character belongs to others .Means all the other people will have only read access to the file .


Number	PermissionType	Symbol
0	No Permission	—
1	Execute	–x
2	Write	-w-
3	Execute+Write	-wx
4	Read	      r–
5	Read+Execute	r-x
6	Read+Write	rw-
7	read+Write+Execute	rwx

chmod command:
Lets say you have a file devops.txt and you want to give below permissions :This can either be done in numeric or symbolic way
Read,write,execute to User
read and write to group
no permission to other 
This can be acheived using the command (chmod 760 devops.txt) ==>this in numeric way


Now lets talk about how to change owner and group in linux:
chown user filename ==> Now the filename will be owned by user (lets say kriti)
chown user:group filename ==>changing both the user and group of file
chgrp group_name filename  ==>If you want to just change the group name for file

su ---> To switch user: su kriti(switch user to kriti)
Assignments:
1. Create three users A,B and C. 
2. Create a group D , assign B and C user to that group.
3. Create a file devops.txt with user A.
4. Give Read,write and execute permission to Group D for devops.txt.Check if User B can modify the content of file and save it .
5. Change the owner of devops.txt to User C.