tty -> For know your terminals

pwd -> To Know the present workind dir.

ls -> To see the files of dir.

ls -a -> To see the hidden files.

if you want to create hidden file then try this
touch .file name/dir.Name

touch -> for creating the balnk file
touch file name

cat -> Multi purpose

1. cat >> file name -> To write the cotent in file
2. cat file name -> To see the file content
3. Cat >> file name -> To add content in pre. file

cp -> for copy the content of one file to another file

1. cp s.f. d.f.

rm-> To Remove the file from dir.
rm File Name

mkdir -> To Make a New dir

mkdir FIle name

Home directory of admin /root.

home dir. of the user /home/username

*****For user details******

1.vim /etc/passwd

2.all user will disply. by default 0 to 499 user are sytem user & 500 are the local users.

3.we can change group id, default dir & default shall

4. when you change the default dir, dir must be exits

*****For user password details

1. vim /etc/shadow

***** For the Group details******

1. vim /etc/group


***** For change the user defaults settings*******

1. vim /etc/defaults/useradd

1. useradd or usermode -s /sbin/nologin username --> user will nt login

2. useradd or usermode -d /home/pankil username --> users default directory

3. useradd or usermode -u 4532 user name --> for change the group id

# rm -f bash*

# then cp /etc/skel/.bash* user dir:.