Important Stuff

CentOS Linux -  is a rebranding of RedHat Linux.

Shell = A program that allows user to interact with operating system.

touch = creates a new empty file

nano = text file editing

rm  = delete a file

pwd = tells you where you are in the Linux directory hierarchy

~  = Its stands for the home directory of the logged-in user

Pipe  = takes the output of a command and sends it to the input of another command

man hier  = list all the directories

whoami  = displays the user you are logged in as

Filesystem Hierarchy

• /etc  = all executable programs or shell commands

• /usr  = Stores application programs

• /var =  Stores log files, mails and other data

• /tmp = Stores temporary files

Pathnames:

• Absolute  = starts with '/' character

• Relative = starts with some other directory name

Globbing = using wildcards in a shell command

Synopsis =  the name(s) that can be used to invoke the command

Command that will show all files and sub-directories in  a directory, whether hidden or not ?

ls -a  

/etc/skel - templete for new user home directory (created by the useradd utility)

How to change home directory of /etc/skel into another name "such as for developers home directories" ?

1) Search for ( man useradd )

2) The syntax, to change the home directory of "lhaxor" to /etc/skel-dev :

# useradd -k /etc/skel-dev -m lhaxor

3) Fill the account's with the users full name "Leet Haxor" :

# useradd -c "Leet Haxor" -k /etc/skel-dev -m lhaxor

... the -m will check and see if user was already created, in order to not delete the users past data

Add, Leet to groups "sshers" and "secret" ?

1) This is the syntax, that will change Leet's existing group memberships :

# usermod -aG sshers,secret lhaxor

~   - (Tilde) means go to home directory

So for example (need to be root):

# cd ~bob

...This will take you to the home directory of "Bob"