Goals: Introduction to the Linux File System, its structure and how to navigate around it, as well as creating, moving and copying files and folders.

What the file system is, and a typical organization / hierarchy.
Some high-level comparison to that of Windows.
Absolute vs relative paths.
Commands: pwd, cd, ls, mv, cp, mkdir, rmdir, rm
History: history
File Ownership and Permissions.

Some high-level comparison to that of Windows

	Windows	Linux
Structure	Uses (data) drives C:, D:, E:…	Uses a tree hierarchy starting at “`/`” Known as the root directory.
	`<drive>\<folder01>\<folder02>`	`/<folder01>/<folder02>`
Syntax	Uses the back slash: “\”	Uses the forward slash: “/”
Home folder	`C:\Users\<username>`	`/home/<username>`
Application Install	`C:\Program Files\`	`/usr/`
Folder and Filenames	Case insensitive: FoLdEr = FOLDER	Case sensitive: FoLdEr ≠ FOLDER
		Wherever you are within the hierarchy is known as your current working directory (cwd)

Linux OS General Structure

Linux Hierarchical Structure: Example

Absolute Path: /home/arcc-t05/

Path starts with a “/”

Absolute Path: /home/arcc-t05/workshop/projects/p01/etc/

Relative Path: workshop/projects/p01/etc/

Path does not start with a “/”

Relative Path: p01/etc/

Ex: Starting at / (root), what is the absolute path to the bits folder?

Answer:

Answer

/usr/include/bits/

Ex: Starting in the home folder what is the relative path to the Jan folder?

Answer:

Answer

arcc-t05/workshop/data/2023/Jan/

If you are following along as part of a scheduled training or bootcamp, please replace the arccanetrain directory with the project directory you’ve been provided for your specific training/bootcamp. If you are training independently, please use your own project folder, but contact arcc-help@uwyo.edu if you would like a copy of the files and directories used in our examples.

Commands:

Used to perform certain operating system tasks through the Command Line Interface, as directed by the interpreter (as opposed to a Graphical Interface Interpreter we would usually use).

<command --help>

Command	Description
pwd	pwd: pwd [-LP] Print the name of the current working directory.
cd	cd: cd [-L\|[-P [-e]] [-@]] [dir] Change the shell working directory.
ls	Usage: ls [OPTION]... [FILE]... List information about the FILEs (the current directory by default)
mkdir	Usage: mkdir [OPTION]... DIRECTORY... Create the DIRECTORY(ies), if they do not already exist.
mv	Usage: mv [OPTION]... [-T] SOURCE DEST or: mv [OPTION]... SOURCE... DIRECTORY or: mv [OPTION]... -t DIRECTORY SOURCE... Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY

Commands: <command --help>

Command	Description
cp	Usage: cp [OPTION]... [-T] SOURCE DEST or: cp [OPTION]... SOURCE... DIRECTORY or: cp [OPTION]... -t DIRECTORY SOURCE... Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.
rmdir	Usage: rmdir [OPTION]... DIRECTORY... Remove the DIRECTORY(ies), if they are empty.
rm	Usage: rm [OPTION]... [FILE]... Remove (unlink) the FILE(s).

pwd: Print the name of the current working directory

If you get lost, then you can jump back to the home folder.

[arcc-t05@blog1 ???]$ cd
[arcc-t05@blog1 ~]$

The ~ “tilda” character represents your home directory.

Use the pwd to confirm your current working directory, which after the above command will be home.

[arcc-t05@blog1 ~]$ pwd
/home/arcc-t05

cd: Change the shell working directory

Start by navigating back to home.

[arcc-t05@blog1 ???]$ cd
[arcc-t05@blog1 ~]$

Move up one level, into the current folder’s parent.

[arcc-t05@blog1 ~]$ cd ..
[arcc-t05@blog1 ~]$ pwd
/home

Move up another level into the root folder.

[arcc-t05@blog1 home]$ cd ..
[arcc-t05@blog1 /]$ pwd
/

cd: Change working directory (cont)

Navigate into the opt folder.

[arcc-t05@blog1 /]$ cd opt
[arcc-t05@blog1 opt]$ pwd
/opt

Question: Did we define an an absolute or relative path?

Answer:

Did we define an an absolute or relative path?

Answer

When we print out the working directory, we are presented with a '/' in front of opt, however when we changed directories to opt, our cd command did not have a '/'. Therefore, we defined the relative path to the opt directory.

cd: Change the shell working directory

First reset back to home.

[arcc-t05@blog1 opt]$ cd
[arcc-t05@blog1 ~]$

Navigate into the /usr/include/asm folder.

[arcc-t05@blog1 ~]$ cd /usr/include/asm
[arcc-t05@blog1 asm]$ pwd
/usr/include/asm

Question: Did we define an absolute or relative path?

Answer:

Answer

Relative path, since we specified the full path, starting with root: /

Navigate up two levels:

[arcc-t05@blog1 asm]$ cd ../..
[arcc-t05@blog1 usr]$ pwd
/usr

Navigate back home:

[arcc-t05@blog1 usr]$ cd
[arcc-t05@blog1 ~]

ls: List information about the FILEs (cwd by default)

Take a look at the ls command and some of the options it provides.

List files in the user’s home folder.

[arcc-t05@blog1 ~]$ ls

List long format that includes ownership and permission details.

[arcc-t05@blog1 ~]$ ls -l

List all files, including hidden files and folders start with “.”.

Notice how ‘short-name’ options are grouped.

[arcc-t05@blog1 ~]$ ls –a

List all files with long format.

[arcc-t05@blog1 ~]$ ls –al

List all files with long format, in reverse order.

[arcc-t05@blog1 ~]$ ls –alr

List all files with long format, in reverse order, in human readable form.

arcc-t05@blog1 ~]$ ls –alrh

Note how we can use multiple options together.

Demonstrate how to ls to a folder outside cwd using an absolute path.

# Demonstrate how to ‘ls’ to a folder outside cwd
[~]$ ls /project/arccanetrain/arcc-t01
folder01  myfile.txt

mkdir: Create the DIRECTORY(ies), if they do not already exist

$ cd
[~]$ ls
Desktop  Documents  Downloads
[~]$ mkdir folder01
[~]$ ls
Desktop  Documents  Downloads  folder01
[~]$ mkdir folder01
mkdir: cannot create directory ‘folder01’: File exists
[~]$ cd folder01/
[folder01]$ pwd
/home/arcc-t05/folder01

If a folder already exists, you can not make it again.

mkdir: Create the DIRECTORY(ies), if they do not already exist

[folder01]$ mkdir folder02 folder03
[folder01]$ ls
folder02 folder03
[folder01]$ cd folder02/
[folder02]$ pwd
/home/arcc-t05/folder01/folder02
[folder02]$ cd ../..
[~]$ pwd
/home/arcc-t05

mv: Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY

$ cd
# Create an empty file.
[~]$ touch myfil.txt
[~]$ ls
Desktop  Documents  Downloads  folder01  myfil.txt
# Rename the file ‘myfil.txt’ to ‘myfile.txt’:
[~]$ mv myfil.txt myfile.txt 
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile.txt

Notice how we have moved the file from one name to a new name - essentially renaming it.

mv: Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY

# Move the file ‘myfile.txt’ into the directory ‘folder01’
[~]$ mv myfile.txt folder01/
[~]$ ls
Desktop  Documents  Downloads  folder01
# Demonstrate how to ‘ls’ what is in a relative folder.
[~]$ ls folder01/
folder02  myfile.txt

cp: Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY

# Navigate back to home:
$ cd

# Use the touch command to create an empty file.
[~]$ touch myfile02.txt
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile02.txt

# Copy (duplicate) a file.
[~]$ cp myfile02.txt myfile02b.txt 
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile02b.txt  myfile02.txt

# Copy a file into an existing folder.
[~]$ cp myfile02b.txt folder01/
[~]$ ls folder01/
folder02  myfile02b.txt  myfile.txt

cp: folders

[~]$ cp folder01
cp: missing destination file operand after 'folder01'
Try 'cp --help' for more information.
[~]$ ls folder01
folder02  myfile02b.txt  myfile.txt
[~]$ cp folder01 folder03
cp: -r not specified; omitting directory 'folder01’

You can not use the cp command with no options to copy a folder that has files within it.

Look at the options available. cp -h

In this specifically -r that recursively copy a folder and all its contents.

[~]$ cp –r folder01 folder03
[~]$ ls
Desktop  Documents  Downloads  folder01  folder03 myfile02b.txt  myfile02.txt
[~]$ ls folder03
folder02  myfile02b.txt  myfile.txt

rmdir: Remove the DIRECTORY(ies), if they are empty

[~]$ ls 
Desktop  Documents  Downloads  folder01  folder03  myfile02b.txt  myfile02.txt
[~]$ mkdir folder04
[~]$ ls
Desktop  Documents  Downloads  folder01  folder03  folder04  myfile02b.txt  
myfile02.txt

# Can remove folder04 since it is empty.
[~]$ rmdir folder04
[~]$ ls
Desktop  Documents  Downloads  folder01  folder03  myfile02b.txt  myfile02.txt

[~]$ rmdir folder03/
rmdir: failed to remove 'folder03/': Directory not empty

You can not use rmdir to remove a directory that has files still within it. The folder must be empty.

rm: Remove (unlink) the FILE(s)

[~]$ cd
[~]$ cd folder03
[folder03]$ ls
folder02  myfile02b.txt  myfile.txt

[folder03]$ ls folder02/
[folder03]$
# ‘folder02’ is empty.
[folder03]$ rmdir folder02/

[folder03]$ ls
myfile02b.txt  myfile.txt
[folder03]$ rm myfile.txt 
[folder03]$ ls
myfile02b.txt
[folder03]$ rm myfile02b.txt

rm: Remove (unlink) the FILE(s)

[folder03]$ ls
[folder03]$
# ‘folder03’ is now empty.
[folder03]$ cd ..
[~]$ rmdir folder03/
[~]$ ls
Desktop  Documents  Downloads  folder01  myfile02b.txt  myfile02.txt
# This has taken a lot of individual steps.
# Can we do this quicker?

rm: folders and file(s)

[~]$ cd
[~]$ rm folder01/
rm: cannot remove 'folder01/': Is a directory

You can not use the rm command with no options to remove a folder.

[~]$ rm --help
Usage: rm [OPTION]... [FILE]...
Remove (unlink) the FILE(s).
...
  -r, -R, --recursive   remove directories and their contents recursively
...

Using help we found we can use the -r option to remove a folder and all its contents.

[~]$ rm -r folder01/
[~]$ ls
Desktop  Documents  Downloads  myfile02b.txt  myfile02.txt
# Can remove multiple files.
[~]$ rm myfile02b.txt myfile02.txt 
[~]$ ls
Desktop  Documents  Downloads
# Alternatively we could have removed above 2 files with: rm myfile* 
# * is a wildcard, so the rm myfile* will remove all starting with the characters "myfile"

rm: WARNING

From the command-line there is NO trash bin.

Using rm/rmdir is FINAL!

history

[~]$ history --help
history: history [-c] [-d offset] [n] or history -anrw [filename] or history -ps arg [arg...]
    Display or manipulate the history list.
    ...
[~]$ history 
  ...	
  219  rm -f folder01/
  220  rm -r folder01/
  221  ls
  222  rm myfile02b.txt myfile02.txt 
  223  ls
  224  history
# Repeat command ‘223’
[arcc-t05@blog1 ~]$ !223
ls
Desktop  Documents  Downloads

Exercises

Questions:

How can you return to your home folder?
What command do you use if you’ve forgotten where you are in the folder hierarchy?
How can you list what is in a folder as well as any subfolders?
Go back through the command related slides are try for yourself.

Answers

1: How can you return to your home folder?

Answer

Use: cd or cd ~ as a shortcut to return to your home folder instead of using a cd /home/$USER or cd /home/<insert_your_username>/
cd stands for: change directory

2: What command do you use if you’ve forgotten where you are in the folder hierarchy?

Answer

Use: pwd
This stands for: print working directory.

3: How can you list what is a folder as well as any subfolders?

Answer

ls command lists contents, which flag do we use to get it’s subfolders as well?

[]$ man ls
-R, --recursive
              list subdirectories recursively
[]$ ls -R

-R is for recursive, which relates to repeated application of the rule over successive executions. We continue applying the listings for all subfolders that exist within the top level parent directory.

File Ownership and Permissions

What does the output of ls –l mean?

[arcc-t05@blog1 ~]$ cd /project/arccanetrain/intro_to_linux
[arcc-t05@blog1 intro_to_linux]$ ls -al
total 54
drwxrwsr-x  4 salexan5 arccanetrain  4096 Oct  6 08:09 .
drwxrws--- 40 root     arccanetrain  4096 Oct  6 08:09 ..
drwxrwsr-x  2 salexan5 arccanetrain  4096 Oct  5 11:19 clusters
drwxrwsr-x  6 salexan5 arccanetrain  4096 Oct  5 14:56 data
-rw-rw-r--  1 salexan5 arccanetrain   874 Oct  5 15:30 fruits.txt
-rw-rw-r--  1 salexan5 arccanetrain 34472 Oct  5 10:57 software.csv
-rw-rw-r--  1 salexan5 arccanetrain  1603 Oct  6 08:08 vegatables.txt
-rw-rw-r--  1 arcc-t05 arccanetrain    26 Oct  5 07:20 workshop_all.txt
-rw-------  1 arcc-t05 arccanetrain    23 Oct  5 07:20 workshop_me.txt

The first character on the left indicates if it is a directory “d” or a file “-”.

drwxrwsr-x    clusters          # A folder.
-rw-rw-r--    workshop_all.txt  # A file.

File Ownership and Permissions

-rw-rw-r--    1 arcc-t05 arccanetrain     26 Oct  5 07:20 workshop_all.txt

User: This is the owner of the file/folder. By default, the person who created it becomes its owner.
- arcc-t05 is the owner
Group: A group is a collection of users. The primary purpose of the group is to define a set of privileges for a given resource that can be shared among the users within the group.
- arccanetrain is the group.
- All the arcc-txx users have been setup to be within this group.
Other: This is any other user who has access to the file/folder. This person has neither created the file, nor do they belong to a user group.

Permission Denied

This demonstrates how permissions work. Bare in mind this assumes you’re logged in as user arcc-t05.

[]$ cd /project/arccanetrain/
[]$ ls -al
...
# drwxr-sr-x    2 arcc-t01 arccanetrain   4096 May 16 16:26 arcc-t01
...

The middle set of permissions is “drwxr-sr-x” means no one other than arcc-t01 has permission to write within this folder.

[arccanetrain]$ cd arcc-t01/
# Can arcc-t05 create (write) a file within this folder?
[arcc-t01]$ touch text.txt
touch: cannot touch 'text.txt': Permission denied

No one, other than arcc-t01 can create (write) a file within this folder.

If we change directories, and go to /project/arccanetrain/intro_to_linux, what permissions do the contents of this directory have?

[arcc-t01]$ cd ../intro_to_linux
[arcc-t01]$ ls -al
# -rw-rw-r--    1 arcc-t05 arccanetrain     26 Oct  5 07:20 workshop_all.txt

Any user within the arccanetrain group can read/write the file workshop_all.txt.

Everybody can read it. Do you want anyone outside of this project to be able to read this file?

[] ls -al
# -rw-------    1 arcc-t05 arccanetrain     23 Oct  5 07:20 workshop_me.txt
[intro_to_linux]$ cat workshop_me.txt
cat: workshop_me.txt: Permission denied

Only user arcc-t05 can read/write this file. No one else, not even anyone within the arccanetrain group, can view this file.

Exercise: Try it

[]$ cd /project/arccanetrain/
[arccanetrain]$ cd arcc-t05
[arcc-t05]$ touch test.txt
# Do you get a “Permission denied”?
# Navigate into the intro_to_linux folder. 
[arcc-t05]$ cd ../intro_to_linux
[intro_to_linux]$ cat workshop_all.txt
Everybody can read this.
[intro_to_linux]$ cat workshop_me.txt
# Do you get a “Permission denied”?
# Can you cd into the /opt folder?
# Justify your answer.
# Can you cd into the /root folder?
# Justify your answer.

Answers

Can you cd into the /opt folder?

Answer

[arcc-t05@blog1 ~]$ cd /opt
[arcc-t05@blog1 opt]$

Yes

Can you cd into the /root folder?

Answer

[arcc-t05@blog1 ~]$ cd /root
-bash: cd: /root: Permission denied
[arcc-t05@blog1 ~]$ ls -l /
...
# “other” has read permissions
drwxr-xr-x.    5 root root    43 Jun 26 11:47 opt
...
# No permission set for other read permissions
dr-xr-x---.   17 root root  4096 Oct  4 12:58 root

No

Next Steps

Previous

Using the Terminal

Workshop Home

Intro to Linux CLI: The File System

Next

Summary

The Linux File System

Some high-level comparison to that of Windows

Linux OS General Structure

Linux Hierarchical Structure: Example

Absolute Path: /home/arcc-t05/

Absolute Path: /home/arcc-t05/workshop/projects/p01/etc/

Relative Path: workshop/projects/p01/etc/

Relative Path: p01/etc/

Ex: Starting at / (root), what is the absolute path to the bits folder?

Answer:

Ex: Starting in the home folder what is the relative path to the Jan folder?

Answer:

Commands:

<command --help>

Commands: <command --help>

pwd: Print the name of the current working directory

cd: Change the shell working directory

cd: Change working directory (cont)

Answer:

cd: Change the shell working directory

Answer:

ls: List information about the FILEs (cwd by default)

mkdir: Create the DIRECTORY(ies), if they do not already exist

mkdir: Create the DIRECTORY(ies), if they do not already exist

mv: Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY

mv: Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY

cp: Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY

cp: folders

rmdir: Remove the DIRECTORY(ies), if they are empty

rm: Remove (unlink) the FILE(s)

rm: Remove (unlink) the FILE(s)

rm: folders and file(s)

rm: WARNING

history

Exercises

Answers

File Ownership and Permissions

File Ownership and Permissions

Permission Denied

If we change directories, and go to /project/arccanetrain/intro_to_linux, what permissions do the contents of this directory have?

Exercise: Try it

Answers

Next Steps