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?

Ans: /usr/include/bits/

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

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

Commands: <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
/

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?

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?

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?

Use: cd or cd ~

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

Use: pwd

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

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

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.

[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.

Answer

# Can you cd into the /opt folder?
[arcc-t05@blog1 ~]$ cd /opt
[arcc-t05@blog1 opt]$
# Can you cd into the /root folder?
[arcc-t05@blog1 ~]$ cd /root
-bash: cd: /root: Permission denied
# Justify your answer.
[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

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?

Ans: /usr/include/bits/

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

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

Commands: <command --help>

Commands: <command --help>

pwd: Print the name of the current working directory

cd: Change the shell working directory

cd: Change the shell working directory

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

Exercise: Try it

Answer

Next Steps