Linux Command Line Interface for Beginners I
The operating system of the MSU HPC is Ubuntu, which is a distribution of Linux. So if you want to use our system, it is essential to equip some basic knowledge of Linux. Even though Linux supports a GUI, most works are done on a terminal via text. The Linux command line is a text interface to Linux.
We will walk through some practical exercises to become familiar with a few basic commands and concept.
Navigation
Let's run the first command. Type pwd
and pressing the Enter or
Return key to run it (From now, I'll not mention pressing
Enter/Return key to run a command).
pwd
/mnt/home/iamsam/
You will see a path such as /mnt/home/user/your_id
pwd
is an abbreviation of 'print working directory'. It prints out
the shell's current working directory. You can change the working
directory using the cd
command, an abbreviation for 'change
directory'.
cd /
pwd
/
Now your working directory is '/' which is the root directory. There is nothing much you can do on the root directory, so let's go to your 'home' directory.
cd
pwd
/mnt/home/iamsam/
Regardless of your location, when you just type cd
, you will be
home. You can also type cd \~
instead of cd
to be back your
home.
To go the previous directory, type cd -
cd -
pwd
/
The root directory has many subdirectories including your home directory. Let's go to the 'bin' directory.
cd bin
pwd
/bin
To go up to the parent directory (it is / for us now), use the special
syntax of two dots with cd
such as
cd ..
pwd
/
To go up to the previous directory, use -
with cd
such as
cd -
pwd
/bin
You can use ..
more than once if you have to move up multiple levels
of parent directories.
cd ../..
pwd
Relative and absolute Paths
A path is an address of a directory. Most of the examples we've looked
at so far use relative paths. So your final location is decided based on
your current working directory. However, sometimes you want to use an
absolute path than a relative one. Your home's absolute path at HPC is
/mnt/home/your_id
. See the example to find how to use a relative and
absolute path.
cd /
pwd
/
cd -
pwd
/mnt/home/iamsam
cd /
cd /mnt/home/iamsam
pwd
/mnt/home/iamsam
Creating and removing directories
To make a directory, use mkdir
(short for 'make directory') such as
mkdir temp01
ls
temp01
ls
is a command to list files and folder. We will learn it in a
minute. You can create multiple directories as well.
mkdir temp02 temp03 temp04
ls
temp01 temp02 temp03 temp04
To make a subdirectory, use with -p
option such as
mkdir -p temp04/temp05/temp06
ls temp04
temp05
To remove directory use rm
command with -r
. Without -r
option,
rm will not delete directories (but you can delete files). -r
means
recursive.
rm temp04
rm: cannot remove 'temp04': Is a directory
rm -r temp04
Creating and removing files
You can use editors to create files, but it is out of scope of this
tutorial. Let's use ls
and a pipe >
(we will explain pipes
later).
ls
temp01 temp02 temp03
ls > list.txt
ls
list.txt temp01 temp02 temp03
Now we have three directories (temp01
, temp02
, temp03
) and one file
(list.txt
). We already know how to delete directories. To delete files,
we use command rm
such as
rm list.txt
ls
temp01 temp02 temp03
Copying and renaming directories and files
To copy files or directories, use cp
such as
cp list.txt list2.txt
ls
list.txt list2.txt temp01 temp02 temp03
With the -r
option, you can copy files and directories recursively, i.e.,
copy subdirectories and files.
The mv
command moves files/directories or renames them.
mv list2.txt temp01
ls
list.txt temp01 temp02 temp03
ls temp01
list2.txt
cd temp01
mv list2.txt list3.txt
ls
list3.txt
Listing directories and files
We already used ls. To list directories and files, us ls (short for 'list').
ls
temp01 temp02 temp03
There are many options for ls
. Most frequently used options are
-a
: list all files and directories including hidden contents-h
: print sizes in human readable format (e.g.: 1K, 2.4M, 3.1G)-l
: list with a long listing format-t
: sort my modification time
You can use options separately like ls -l -a -t
or together like
ls -lat
.
ls -l -a -t
total 8
-rw-r--r-- 1 iamsam staff 30 Mar 23 15:37 list.txt
drwxr-xr-x 6 iamsam staff 192 Mar 23 15:37 .
drwxr-xr-x 2 iamsam staff 64 Mar 23 15:37 temp03
drwxr-xr-x 2 iamsam staff 64 Mar 23 15:37 temp02
drwxr-xr-x 2 iamsam staff 64 Mar 23 15:37 temp01
drwxr-xr-x+ 113 iamsam staff 3616 Mar 23 15:21 ..
ls -lat
total 8
-rw-r--r-- 1 iamsam staff 30 Mar 23 15:37 list.txt
drwxr-xr-x 6 iamsam staff 192 Mar 23 15:37 .
drwxr-xr-x 2 iamsam staff 64 Mar 23 15:37 temp03
drwxr-xr-x 2 iamsam staff 64 Mar 23 15:37 temp02
drwxr-xr-x 2 iamsam staff 64 Mar 23 15:37 temp01
drwxr-xr-x+ 113 iamsam staff 3616 Mar 23 15:21 ..
Exercises
Now let's do some exercises.
- Log in your MSU HPC account and go to any dev-node.
- Create a
linux_tutorial
dir on your home. - Copy a folder and contents for this tutorial from
/mnt/research/common-data/workshops/intro2Linux_iamsam
tolinux_tutorial
dir on your home- Go to
linux_tutorial
- Find a hidden directory and rename it to
not_hidden
- Check the contents of
not_hidden
- Create a new directory called
new_dir
- Copy the file
youfoundit.txt
intonew_dir
- Remove
garbage
dir
This is an answer (not including the login process).
mkdir linux_tutorial
cp -r /mnt/research/common-data/workshops/intro2Linux_iamsam linux_tutorial
cd linux_tutorial
ls -a
mv .hidden not_hidden
ls not_hidden
mkdir new_dir
cp not_hidden/youfoundit.txt new_dir
rm -r garbage