Red Hat Enterprise Linux 7 Implementation

File System Navigation

Module Topics

Linux File System
Important Linux Directories
Symbolic Link Directories
File Management
Create Directories
Copy, Move, and Remove Files and Directories
Create Hard Links
Create Soft Links

Linux File System

File System Hierarchy

File systems organized into a single inverted tree of directories
Root of tree is at top of hierarchy
- Branches of directories and subdirectories are below

Linux File System

Directory Structure and Naming

/ is root directory at top of file system hierarchy
/ character also used as directory separator in file names
- Example: etc subdirectory of / is /etc
- Example: issue file within /etc is /etc/issue
Subdirectories of / are used for standard purposes to organize files
- Example: In / root directory, /boot stores files needed to boot system

Linux File System

File System Terms

Static: Content that remains unchanged until explicitly edited or reconfigured
Dynamic or variable: Content that is modified or appended by active processes
Persistent: Content, particularly configuration settings, that remains after a reboot
Runtime: Process- and system-specific content and attributes that are cleared during a reboot

Important Linux Directories

Location

Purpose

/usr

Installed software, shared libraries, include files, and static read-only program data. Important subdirectories include:

/usr/bin: User commands
/usr/sbin: System administration commands
/usr/local: Locally customized software

/etc

Configuration files specific to system.

/var

Variable data specific to system that should persist between boots. Under /var are files that dynamically change.

Examples: Databases, cache directories, log files, printer-spooled documents, and website content.

/run

Runtime data for processes started since last boot. Includes process ID files and lock files. Contents of /run is recreated on reboot.

/run consolidates /var/run and /var/lock from older versions of Red Hat Enterprise Linux.

/home

Where regular users store personal data and configuration files.

/root

Home directory for root, the administrative superuser.

/tmp

World-writable space for temporary files. Files that are not accessed, changed, or modified for 10 days are deleted automatically.

/var/tmp is also a temporary directory in which files that have not been accessed, changed, or modified in more than 30 days are deleted automatically.

/boot

Contains files needed to start boot process.

/dev

Contains special device files that are used by system to access hardware.

Symbolic Link Directories

Older directories in / now have the same content as their counterparts in /usr:
- /bin and /usr/bin
- /sbin and /usr/sbin
- /lib and /usr/lib
- /lib64 and /usr/lib64
Formerly these were distinct directories with different files
Directories in / are symbolic links to matching directories in /usr

References

hier(7) man page
Filesystem Hierarchy Standard

File Management

This table describes common file management commands and how they are used in single-source and multiple-source situations.

Task

Single Source ^(note)

Multiple Source ^(note)

Copy file

cp file1 file2

cp file1 file2 file3 dir ⁽⁵⁾

Move file

mv file1 file2 ⁽¹⁾

mv file1 file2 file3 dir ⁽⁴⁾

Remove file

rm file1

rm -f file1 file2 file3 ⁽⁵⁾

Create directory

mkdir dir

mkdir -p par1/par2/dir ⁽⁶⁾

Copy directory

cp -r dir1 dir2 ⁽²⁾

cp -r dir1 dir2 dir3 dir4 ⁽⁴⁾

Move directory

mv dir1 dir2 ⁽³⁾

mv dir1 dir2 dir3 dir4 ⁽⁴⁾

Remove directory

rm -r dir1 ⁽²⁾

rm -rf dir1 dir2 dir3 ⁽⁵⁾

⁽¹⁾The result is a rename. ⁽²⁾The recursive option is required to process a source directory. ⁽³⁾If dir2 exists, the result is a move. If dir2 does not exist, the result is a rename. ⁽⁴⁾The last argument must be a directory. ⁽⁵⁾Use caution with the force option. You are not prompted to confirm your action. ⁽⁶⁾Use caution with the create-parent option. Typing errors are not reported or corrected.

Create Directories

Use mkdir to create directories and subdirectories
Error conditions:
- Name already exists
- Parent directory does not exist
Use -p to create missing parent directories for requested destination
- Spelling and typing mistakes create unintended directories without generating error messages

Example: mkdir error condition

[student@desktop1 ~]$ mkdir Video/Watched
mkdir:cannot create directory `Video/Watched': No such file or directory

Create Multiple Directories

[student@desktop1 ~]$ mkdir Videos/Watched
[student@desktop1 ~]$ cd Documents
[student@desktop1 Documents]$ mkdir ProjectX ProjectY
[student@desktop1 Documents]$ mkdir -p Thesis/Chapter1 Thesis/Chapter2 Thesis/Chapter3
[student@desktop1 Documents]$ cd
[student@desktop1 ~]$ ls -R Videos Documents
Documents:
ProjectX  ProjectY  Thesis  thesis_chapter1.odf  thesis_chapter2.odf

Documents/ProjectX:

Documents/ProjectY:

Documents/Thesis:
Chapter1  Chapter2  Chapter3

Documents/Thesis/Chapter1:

Documents/Thesis/Chapter2:

Documents/Thesis/Chapter3:

Videos:
blockbuster1.ogg  blockbuster2.ogg  Watched

Videos/Watched:

[student@desktop1 ~]$

Copy Files

Use cp to copy one or more files to new, independent files
- Copy file to new file in current directory or another
- Copy multiple files to another directory

New file names must be unique

If new file name is not unique, cp overwrites existing file

[student@desktop1 ~]$ cd Videos
[student@desktop1 Videos]$ cp blockbuster1.ogg blockbuster3.ogg
[student@desktop1 Videos]$ ls -l
total 0
-rw-rw-r--. 1 student student    0 Feb  8 16:3 blockbuster1.ogg
-rw-rw-r--. 1 student student    0 Feb  8 16:4 blockbuster2.ogg
-rw-rw-r--. 1 student student    0 Feb  8 19:2 blockbuster3.ogg
drwxrwxr-x. 2 student student 4096 Feb  8 23:5 Watched
[student@desktop1 Videos]$

Copy Multiple Files

When copying multiple files with one command, last argument must be a directory
- Copied files retain original names in new directory
- Conflicting file names at destination result in overwritten files
- To prevent overwriting, multi-file cp ignores directories specified as source
Use -r to copy non-empty directories

Copy Multiple Files

[student@desktop1 Videos]$ cd ../Documents
[student@desktop1 Documents]$ cp thesis_chapter1.odf thesis_chapter2.odf Thesis ProjectX
cp:omitting directory `Thesis'
[student@desktop1 Documents]$ cp -r Thesis ProjectX
[student@desktop1 Documents]$ cp thesis_chapter2.odf Thesis/Chapter2/
[student@desktop1 Documents]$ ls -R
.:
ProjectX  ProjectY  Thesis  thesis_chapter1.odf  thesis_chapter2.odf

./ProjectX:
Thesis  thesis_chapter1.odf  thesis_chapter2.odf

./ProjectX/Thesis:

./ProjectY:

./Thesis:
Chapter1  Chapter2  Chapter3

./Thesis/Chapter1:

./Thesis/Chapter2:
thesis_chapter2.odf

./Thesis/Chapter3:
[student@desktop1 Documents]$

Move Files

Use mv to rename files in same directory or relocate files to new directory
File content remains unchanged
To move files to different file system, create new file by copying and then delete source file
- Large files may take longer to move

Move Files

[student@desktop1 Videos]$ cd ../Documents
[student@desktop1 Documents]$ ls -l
total 0
-rw-rw-r--. 1 student student    0 Feb  8 16:4 thesis_chapter1.odf
-rw-rw-r--. 1 student student    0 Feb  8 16:4 thesis_chapter2.odf
[student@desktop1 Documents]$ mv thesis_chapter2.odf thesis_chapter2_reviewed.odf
[student@desktop1 Documents]$ mv thesis_chapter1.odf Thesis/Chapter1
[student@desktop1 Documents]$ ls -lR
.:
total 16
drwxrwxr-x. 2 student student 4096 Feb 11 11:8 ProjectX
drwxrwxr-x. 2 student student 4096 Feb 11 11:5 ProjectY
drwxrwxr-x. 5 student student 4096 Feb 11 11:6 Thesis
-rw-rw-r--. 1 student student    0 Feb 11 11:4 thesis_chapter2_reviewed.odf

./ProjectX:
total 0
-rw-rw-r--. 1 student student 0 Feb 11 11:8 thesis_chapter1.odf
-rw-rw-r--. 1 student student 0 Feb 11 11:8 thesis_chapter2.odf

./ProjectX/Thesis:
total 0

./ProjectY:
total 0

./Thesis:
total 12
drwxrwxr-x. 2 student student 4096 Feb 11 11:9 Chapter1
drwxrwxr-x. 2 student student 4096 Feb 11 11:6 Chapter2
drwxrwxr-x. 2 student student 4096 Feb 11 11:6 Chapter3

./Thesis/Chapter1:
total 0
-rw-rw-r--. 1 student student 0 Feb 11 11:4 thesis_chapter1.odf

./Thesis/Chapter2:
total 0
-rw-rw-r--. 1 student student 0 Feb 11 11:4 thesis_chapter2.odf

./Thesis/Chapter3:
total 0
[student@desktop1 Documents]$

Remove Files

Default syntax for rm deletes files but not directories
To delete directories and subdirectories, use -r
To receive prompt for each deletion, use -i
To force deletion without prompts, use -f

There is no undelete command or trash bin from which to restore.

[student@desktop1 Documents]$ pwd
/home/student/Documents
[student@desktop1 Documents]$ rm thesis_chapter2_reviewed.odf
[student@desktop1 Documents]$ rm Thesis/Chapter1
rm:cannot remove `Thesis/Chapter1': Is a directory
[student@desktop1 Documents]$ rm -r Thesis/Chapter1
[student@desktop1 Documents]$ ls -l Thesis
total 8
drwxrwxr-x. 2 student student 4096 Feb 11 12:7 Chapter2
drwxrwxr-x. 2 student student 4096 Feb 11 12:8 Chapter3
[student@desktop1 Documents]$ rm -ri Thesis
rm:descend into directory `Thesis'? y
rm:descend into directory `Thesis/Chapter2'? y
rm:remove regular empty file `Thesis/Chapter2/thesis_chapter2.odf'? y
rm:remove directory `Thesis/Chapter2'? y
rm:remove directory `Thesis/Chapter3'? y
rm:remove directory `Thesis'? y
[student@desktop1 Documents]$

Remove Directories

To delete only empty directories, use rmdir

Removed directories cannot be undeleted

[student@desktop1 Documents]$ pwd
/home/student/Documents
[student@desktop1 Documents]$ rmdir  ProjectY
[student@desktop1 Documents]$ rmdir  ProjectX
rmdir:failed to remove `ProjectX': Directory not empty
[student@desktop1 Documents]$ rm -r ProjectX
[student@desktop1 Documents]$ ls -lR
.:
total 0
[student@desktop1 Documents]$

References

Man pages: cp(1), mkdir(1), mv(1), rm(1), and rmdir(1)

Hard Links

Hard link: Directory entry that references a file
- Every file has one hard link by default
To save space, create hard link instead of copying file
If created in same directory as existing hard link, hard link must have different file name
- Or create hard link in different directory
All hard links pointing to file have same:
- Permissions
- Link count
- User/group ownerships
- Time stamps
- Content
Hard links pointing to file must be on same file system

Create Hard Links

To show hard link count, use ls -l

Count appears after permissions and before file owner

[root@server1 ~]# echo "Hello World" > newfile.txt
[root@server1 ~]# ls -l newfile.txt
-rw-r--r--. 1 root root 0 Mar 11 19:9 newfile.txt

To create hard link to file, use ln
- ln expects existing file as first argument, followed by one or more hard links
Hard links can reside anywhere on same file system as existing file

Note: If you create a hard link, you cannot easily tell that a file is a hard link or where it links to

Create Hard Links

Example: Create hard link newfile-link2.txt for file newfile.txt in same directory

[root@server1 ~]# ln newfile.txt /tmp/newfile-hlink2.txt
[root@server1 ~]# ls -l newfile.txt /tmp/newfile-hlink2.txt
-rw-rw-r--. 2 root root 12 Mar 11 19:9 newfile.txt
-rw-rw-r--. 2 root root 12 Mar 11 19:9 newfile-hlink2.txt

Example: If original file is deleted, content of file is available as long as one hard link exists

[root@server1 ~]# rm -f newfile.txt
[root@server1 ~]# ls -l /tmp/newfile-link2.txt
-rw-rw-r--. 1 root root 12 Mar 11 19:9 /tmp/newfile-link2.txt
[root@server1 ~]# cat /tmp/newfile-link2.txt
Hello World

All hard links referencing a file have the same permissions, link count, user/group ownerships, time stamps, and file contents. Any information changed on one hard link also changes on all other hard links.

Create Soft Links

Soft link: Special file that points to existing file or directory
- Can point to file or directory on another file system

To create a soft, or symbolic, link, use ln -s

[root@server1 ~]# ln -s /root/newfile-link2.txt /tmp/newfile-symlink.txt
[root@server1 ~]# ls -l newfile-link2.txt /tmp/newfile-symlink.txt
lrwxrwxrwx. 1 root root 11 Mar 11 20:9 /tmp/newfile-symlink.txt -> /root/newfile-link2.txt
-rw-rw-r--. 1 root root 12 Mar 11 19:9 newfile-link2.txt

Create Soft Links

Dangling soft link: Soft link pointing to missing file

[root@server1 ~]# rm -f newfile-link2.txt
[root@server1 ~]# ls -l /tmp/newfile-symlink.txt
lrwxrwxrwx. 1 root root 11 Mar 11 20:9 /tmp/newfile-symlink.txt -> newfile-link2.txt
[root@server1 ~]# cat /tmp/newfile-symlink.txt
cat:/tmp/newfile-symlink.txt: No such file or directory

Soft link can point to and act like directory

To change to soft link directory, use cd

Example: Create soft link /root/configfiles pointing to /etc

[root@server1 ~]# ln -s /etc /root/configfiles
[root@server1 ~]# cd /root/configfiles
[root@server1 configfiles]# pwd
/root/configfiles

Reference

ln(1) man page

Summary

Linux File System
Important Linux Directories
Symbolic Link Directories
File Management
Create Directories
Copy, Move, and Remove Files and Directories
Create Hard Links
Create Soft Links

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