1. Manage Directories and Files in Linux

2. Objectives Understand the Filesystem Hierarchy Standard (FHS)
Identify File Types in the Linux System
Change Directories and List Directory Contents
Create and View Files
Manage Files and Directories
Find Files
Search File Content

3. Understand the Filesystem Hierarchy Standard (FHS)
The file system concept of Linux (and, in general, of all UNIX systems) is considerably different than that of other operating systems
To understand the concept of the Linux file system, you need to know the following:
The Hierarchical Structure of the File System
FHS (Filesystem Hierarchy Standard)
Root Directory /
Essential Binaries for Use by All Users (/bin/)
Boot Directory (/boot/)

4. Understand the FHS (continued)
To understand the concept of the Linux file system, you need to know the following (continued):
Device Files (/dev/)
Configuration Files (/etc/)
User Directories (/home/)
Libraries (/lib/)
Mount Points for Removable Media (/media/*)
Application Directory (/opt/)
Home Directory of the Administrator (/root/)
System Binaries (/sbin/)
Data Directories for Services (/srv/)

5. Understand the FHS (continued)
To understand the concept of the Linux file system, you need to know the following (continued):
Temporary Area (/tmp/)
The Hierarchy below /usr/
Variable Files (/var/)
Process Files (/proc/)
System Information Directory (/sys/)
Mount Point for Temporarily Mounted File Systems (/mnt/)
Directories for Mounting Other File Systems

6. The Hierarchical Structure of the File System

7. The Hierarchical Structure of the File System (continued)

8. FHS (Filesystem Hierarchy Standard)
The structure of the file system is described in the Filesystem Hierarchy Standard (FHS)
It specifies which directories must be located on the first level after the root directory and what they contain
It does not specify all details
FHS defines a two-layered hierarchy
The directories in the top layer (immediately below the root directory “/”)
As a second layer, the directories under /usr/ and /var/

9. Root Directory /
The root directory refers to the highest layer of the file system tree
Only directories are located here, not files
When the system is booted, the partition on which this directory is located is the first one mounted
All programs that are run on the system start must be available on this partition
The following directories always have to be on the same partition as the root directory:
/bin/, /dev/, /etc/, /lib/, and /sbin/

10. Essential Binaries for Use by All Users (/bin/)

11. Boot Directory (/boot/)
/boot/ contains static files of the boot loader
These are files required for the boot process (with the exception of configuration files)
The backed-up information for the Master Boot Record (MBR) and the system map files are also stored here
These contain information about where exactly the kernel is located on the partition
This directory also contains the kernel
According to FHS, the kernel can also be located directly in the root directory

12. Device Files (/dev/)
Each hardware component existing in the system is represented as a file in /dev/
The hardware components are addressed via these files by writing or reading to or from one of the files.
Two types of Device Files Exist:
Character special files (or character devices)
‘talks’ to device character-by-character (1 byte at a time)
Examples: printer, virtual terminals, serial devices
Block special files (or block devices)
‘talks’ to device 1 block at a time (1 block can be 512bytes to 312KB)
Examples: Hard disk, floppy disk, CD burners.

13. Device Files (/dev/, continued)

14. Device Files (/dev/, continued)

15. Configuration Files (/etc/)

16. User Directories (/home/)
Every user on a Linux system has his own area in which to create and remove files: its home directory
Individual configuration files can be found in the user’s home directory
If there are no special settings, the home directories of all users are located beneath /home/
The home directory of a user be addressed via “~”

17. Libraries (/lib/)
Shared libraries are removed from the actual program, stored in the system, and only called up when the program runs
The directory /lib/ contains the libraries that are used by programs in the directories /bin/ and /sbin/
The kernel modules (hardware drivers not compiled into the kernel) are located in the directory /lib/modules/
You can find additional libraries below the directory /usr/

18. Mount Points for Removable Media (/media/*)
OpenSuse creates directories such as the following in the directory /media/ (depending on your hardware) for mounting removable media:
/media/cdrom/
/media/cdrecorder/
/media/dvd/
/media/floppy/

19. Home Directory of the Administrator (/root/)
The home directory of the system administrator is not located beneath /home/ like that of a normal user
Preferably, it should be on the same partition as the root directory,“/”
Only then is it guaranteed that the user root can always log in without a problem and have her own configured environment available

20. System Binaries (/sbin/)
Contains important system administration programs
Programs in /sbin/ can also, as a rule, be run by normal users, but only to display configured values

21. System Binaries (/sbin/, continued)

22. Data Directories for Services (/srv/)
The directory /srv/ contains subdirectories filled with data of various services
For example:
The files of the Apache web server are located in the directory /srv/www/
The FTP server files are located in the directory /srv/ftp/

23. Temporary Area (/tmp/)
Various programs create temporary files that are stored in /tmp/ until they are deleted
The Hierarchy below /usr/
According with the FHS, represents a second hierarchical layer

24. Variable Files (/var/)
Contains a hierarchy described in the FHS
This directory and its subdirectories contain files that can be modified while the system is running

25. Variable Files (/var/, continued)

26. System Information Directory (/sys/)
The directory /sys/ provides information in the form of a tree structure on various hardware buses, hardware devices, active devices, and their drivers

27. Mount Point for Temporarily Mounted File Systems (/mnt/)
Standard directory for integrating file systems
It should only be used for temporary purposes
da10:~ # mount /dev/hda7 /mnt
da10:~ # umount /mnt
If you do not include any options with mount, the program tries out several file system formats
To specify a specific file system, use the option -t
If the file system format is not supported by the kernel, the command is aborted, and you receive an error message
In this case, you must compile a new kernel that supports the file system format

28. Directories for Mounting Other File Systems
A directory must exist at the point where you intend to mount the file system
This directory is referred to as the mount point
In most cases, only the user root can mount and unmount directories
Use mount and umount
If you mount a file system to a non-empty directory, existing contents of directory will not be accessible
Mounted file system does not have to be on a local hard disk

29. Directories for Mounting Other File Systems (continued)
The directories listed below cannot be imported from other machines
Some of the directories that can be shared are:

30. Automated Mounting of Removable Media
In past versions of Linux, it was necessary to mount removable media with some command to access them and to unmount them afterwards
This has been automated in current kernel versions

31. Identify File Types in the Linux System
The file types in Linux referred to as normal files and directories are also familiar to other operating systems
Normal Files
Directories
Additional types of files are UNIX-specific
Device Files
Links
Sockets
FIFOs

32. Normal Files
Normal files: a set of contiguous data addressed with one name
This includes all the files normally expected under this term (such as ASCII texts, executable programs, or graphics files)
You can use any names you want for these files—there is no division into filename and file type
A number of filenames still retain this structure, but these are requirements of the corresponding applications, such as a word processing program or a compiler

33. Directories
Directories contain two entries with which the structure of the hierarchical file system is implemented
One of these entries (“.”) points to the directory itself
The other entry (“..”) points to the entry one level higher in the hierarchy

34. Device Files
Each piece of hardware (with the exception of network cards) in a Linux system is represented by a device file
These files represent links between the hardware components or the device drivers in the kernel and the applications
Every program that wants to access hardware must access it through the corresponding device file
The programs write to or read from a device file
The kernel then ensures that the data finds its way to the hardware or can be read from the file

35. Links
Links are references to files located at other points in the file system
Data maintenance is simplified through the use of such links
Changes only need to be made to the original file
The changes are then automatically valid for all links

36. Sockets
A socket refers to a special file with which data exchange between two locally running processes can be implemented through the file system
FIFOs
FIFO (first in first out) or named pipe is a term used for files used to exchange data between processes
The file can exchange data in one direction only

37. Change Directories and List Directory Contents
The prompt of a shell terminal contains the current directory (such as
The tilde (~) indicates that you are in the user’s home directory
Commands: ls cd
pwd

38. ls

39. cd
cd: change directory

40. pwd pwd: print working directory
pwd -P prints the physical directory without any symbolic links

41. Create and View Files
To create and view files, you need to know how to do the following:
Create a New File with touch
View a File with cat
View a File with less
View a File with head and tail

42. Create a New File with touch
touch: changes the time stamp of a file or creates a new file with a size of 0 bytes

43. Create a New File with touch (continued)

44. View a File with cat You can use cat to view the contents of a file
Comparable to the command “type” in DOS
The command must include the filename of the file you want to see

45. View a File with less
less displays the contents of a file page by page
Even compressed files (such as .gz and .bz2) can be displayed

46. View a File with head and tail
Used to view the first or last lines of a file
By default, they show ten lines
head -20 displays the first twenty lines
tail -f displays a continuously updated view of the last lines of a file

47. Manage Files and Directories
In this objective, you learn how to:
Copy and Move Files and Directories
Create Directories
Delete Files and Directories
Link Files

48. Copy and Move Files and Directories (continued)
To copy the contents of proposals/ and all its files, including hidden files and subdirectories, to the existing directory proposals_old/:
To avoid copying the hidden files, do the following:

49. Copy and Move Files and Directories (continued)

50. Create Directories
You can use the command mkdir (make directory) to create new directories
mkdir proposal
Use the option -p to create a complete path
mkdir -p proposal/january

51. Delete Files and Directories
Use rmdir to delete empty directories
rmdir proposal
Use rm to delete files and directories
rm part*
To delete directories (even if not empty)
rm –r testdir
You can use the two options in Table 5-17 with rm
User must have permission to delete file(s)

52. Link Files Each file is described by an inode
To see the inode number you can enter ls –I
Each inode has a size of 128 bytes
An inode contains all the information about the file besides the filename
Link: a reference to a file
Create a hard link using ln, which points to the inode of an already existing file
Hard links can only be used when both the file and the link are in the same file system
Create a symbolic link using ln –s; a symbolic link is assigned its own inode

53. Link Files (continued)

54. Link Files (continued)
A symbolic link can point to a non-existing object if the object and its corresponding name no longer exist
For example, if you erase the file old in the preceding example, in OpenSuse new will be shown in a different color in the output of ls, indicating that it points to a non-existent file
An advantage of symbolic links is that you can create links to directories

55. Find Files
In this objective you learn how to find files and programs using the following commands:
KFind
find
locate
whereis
which
type command

56. KFind

57. KFind (continued)
Table 5-18 shows the results of three different search strings

58. KFind (continued)
Use to narrow search

59. find
Usage: find path criteria action

60. find (continued) Examples: find / -name game
Looks for a file named "game" starting at the root directory (searching all directories including mounted filesystems). The `-name' option makes the search case sensitive. You can use the `-iname' option to find something regardless of case.
find /home -user joe
Find every file under the directory /home owned by the user joe.
find /usr -name *stat
Find every file under the directory /usr ending in "stat".
find /var/spool -mtime +60
Find every file under the directory /var/spool that was modified more than 60 days ago.

61. locate locate is an alternative to find –name Examples:
The package findutils-locate must be installed
find can be quite slow
locate searches through a database previously created (/var/lib/locatedb), making it much faster
The database is automatically created and updated daily by OpenSuse
Use updatedb to update it manually
Examples:
locate letter_Miller
locate umount

62. locate

63. whereis
whereis returns the binaries (option -b), manual pages (option -m), and the source code (option -s) of the specified command
If no option is used, all this information is returned, if the information is available
whereis is faster than find, but it is less thorough
Example:

64. which
which searches all paths listed in the variable PATH for the specified command and returns the full path of the command
It is especially useful if several versions of a command exist in different directories and you want to know which version is executed when entered without specifying a path

65. type command
type command can be used to find out what kind of command is executed when command is entered—a shell built-in command or an external command
The option -a delivers all instances of a command bearing this name in the file system