The mkdir command

The mkdir command makes a directory with the name you specify in your current working directory.

To see what your current working directory is, use the command pwd:

stealth% pwd
/stealth/users/ariel/Mail

To change to another directory as the current working directory, use the cd command.

Once you are in the directory where you want to create a subdirectory, use the command mkdir filename:

stealth% ls
stealth% mkdir stuff
stealth% ls
stuff
stealth% ls -l
total 1
drwxr-xr-x  2 ariel         512 Jul 28 15:34 stuff

The ls before and afterwards shows that a new directory, with the name stuff, has been created, and the ls -l shows that it is indeed a directory.

You will need to use chmod to set the access permissions on the directory to something suitable.

You can use the mkdir command to make directories that do not get put in your current working directory, either by giving a full path to the directory:

stealth% pwd
/stealth/users/ariel
stealth% mkdir /stealth/users/ariel/Mail/morestuff
stealth% ls -l /stealth/users/ariel/Mail/
total 2
drwxr-xr-x  2 ariel         512 Jul 28 15:39 morestuff
drwxr-xr-x  2 ariel         512 Jul 28 15:34 stuff

or by giving a relative path with .. in the path when you want to go into a directory above your current one:

stealth% pwd
/stealth/users/ariel/News
stealth% mkdir ../Mail/evenmorestuff
stealth% ls -l ../Mail/
total 3
drwxr-xr-x  2 ariel         512 Jul 28 15:41 evenmorestuff
drwxr-xr-x  2 ariel         512 Jul 28 15:39 morestuff
drwxr-xr-x  2 ariel         512 Jul 28 15:34 stuff

More information about the mkdir command is available by using the command man mkdir.