Linux File System Online Training by QuontraSolutions

1
Browsing The FileSystem In Linux
Attend Free Demo
2

• The Linux file-system is hierarchical and is made
  of directories, sub-directories and files.
• Directories can contain sub-directories and/or
  files this is a structure used by other
  file-systems, such as Microsoft-based ones
  however the concept originated in UNIX.
• In Linux/Unix, everything is represented as a
  file this includes processes, devices,
  applications, I/O sockets, etc.
• Directories are a file as well, they contain the
  information of any files directly under them,
  hierarchically.

3

• The Linux file-system structure is tree like.
• The file-system begins at a directory named /,
  which is also referred to as the root
  directory.
• The drives representation is different than in
  Windows. There are no C or D drives each drive
  has a Mount Point, which is a location under the
  root (/) directory in which it is represented.
• Mount points can be created by the sys-admin that
  serve as connection points of sort to physical
  devices and/or other file-systemsMost Unix
  systems has the default /mnt directory for
  arbitrary mounts. Linux systems, has the /media
  as an additional default directory for removable
  storage devices

4

• Below is a visual representation of the basic
  Linux file-system structure

5

• Absolute the root of Linuxs file-system is
  represented as / this slash mark will always
  be present when we use absolute pathnames to
  navigate the file-system, for example
  /var/log/messages.log
• The first / in the example above represents the
  root dir, var is a directory sitting directly
  under the root dir and log is a directory under
  var. Finally, messages.log is the name of a
  file which resides in /var/log/.

6

• Relative relative pathnames refers to the
  current location in the file-system as the point
  of origin and not the root directory. Lets
  assume we are in the /var/ directory right now,
  in order to reach messages.log file we will use
  the following path log/messages.log
• Note that there is no / at the beginning of the
  pathname and that it begins with the log
  directory, since we are already inside /var/

7

• Every Linux user has a home directory the home
  dirs reside in /home/ltusernamegt
• The home dir has a few uses and advantages to its
  owner
• It is the directory a user goes to after logging
  into the system.
• It becomes the current working directory after
  login.
• The owning user can freely create files and/or
  directories in it.
• Other users do not have permissions to access a
  home directory not owned by themselves, with the
  exclusion of the user root which is the
  administrative user of the system or other users
  that have been granted special permissions by the
  admin.
• The home dir contains customization files which
  are loaded upon login. (.bash_profile / .bashrc
  and others)
• Contains the history of the shell commands
  executed by the specific user (.bash_history)

8

• There are two commands that aid us with
  navigating through the file-system
• PWD Print Working Directory displays the
  absolute pathname of the current working
  directory
• pwd
• /home/nir
• CD change directory make the specified
  pathname our current working directory. can be
  used with either absolute or relative
  pathnames cd /var/log
• pwd
• /var/log

9

• CD with a relative pathname
• pwd
• /var
• cd log
• pwd
• /var/log
• CD without any pathname will make the users home
  dir the current working directory
• pwd
• /var/log
• cd
• pwd
• /home/nir

10

• Pathname navigations has a few shortcuts to make
  things simpler
• . represents the current working directory,
  for example if the current working dir is
  /var/log/ ls . will display the log files in
  this dir.
• .. represents the parent directory, one level
  above the current working directory following
  the above example, ls .. will display the
  contents of /var/
• represents the home directory, each user and
  their own home. example cd will take the
  user nir into /home/nir/
• - return to the previous working directory
  cd will return to the working directory we
  were in before the last cd command weve
  performed.

11

• The ls command is used to list the contents of
  directories. It has numerous options that allow
  the displaying and sorting of information in a
  few different ways.
• ls command syntax is as follows
• ls -option pathnames
• If no options or arguments are given, ls by
  itself will list the current working directorys
  contents, for example
• ls
• file1 file2 file3

12

• ls has a few additional options to control the
  listing results and sorting
• -a display hidden files
• -i display inode numbers
• -R list sub-directories contents recursively
• -d list the directory details, not the files
  inside of it
• -l display long list
• -t sort by modification time
• -r sort in reverse order
• There are numerous additional options, run ls
  --help to view them.

13

• To see detailed information about the contents of
  a directory use the ls -l command.
• The various fields of this table contains most of
  the information about a file, its permissions and
  times
• ls -l
• drwxrwxr-x 2 nir nir 4096 Jul 19 1358 directory
• -rw-rw-r-- 1 nir nir 135 Jul 19 1342 file1
• -rwxrwxr-- 1 nir nir 35 Jul 19 1342 file2
• -rw-rw-r-- 1 nir nir 200 Jul 19 1342 file3

14

• Metacharacters are characters which are
  interpreted by the shell as more than just any
  regular character.
• These characters include ! ? ltgt
• It is highly recommended to Avoid using
  metacharacters when naming files and/or
  directories it will work but is also likely to
  cause trouble.
• When executing a command in the shell, the shell
  scans the whole command for metacharacters if
  any are found, the shell expands these
  characters to their actual meaning before the
  execution of the command, for example, when
  running the command ls la the shell will
  first interpret the mark into its actual
  meaning, which is the current users home dir and
  then execute ls la /home/ltusernamegt.

15

• The Asterisk characters special meaning is
  zero or more characters this character is also
  known as the Wildcard character, example
• ls
• dfile1 dfile2 directory file1 file2 file3
  kfile9 mfile1
• ls k
• kfile9
• Filenames with a leading dot ( . ), such as
  .bash_profile are categorized as hidden by
  the file-system

16

• The question marks ? special meaning is
  match any single character (except a leading dot
  in hidden files). example
• ls
• afile1 afile2 afile123 afile directory file1
  file2 file3 kfile9 mfile1
• ls afile?
• afile1 afile2

17

• The square brackets special meaning is
  match a set or a range of characters in a single
  position.
• example
• ls
• dfile1 dfile2 directory file1 file2 file3
  kfile9 mfile1
• ls mk
• kfile9 mfile1

18

• cp copy a file to a new file or a list of files
  to a directory
• Syntax
• cp options file(s) filedirectory
• Options
• -i run interactively, ask before overwriting
  files
• -f force copy, overwrite automatically
• -r recursively copy files and sub-directories
• cp file file_new
• ls -l file file_new
• -rw-r--r-- 1 root root 4 Jul 23 2102 file
• -rw-r--r-- 1 root root 4 Jul 23 2211 file_new

19

• mv move or rename a file or move a list of
  files to a directory
• Syntax
• mv options file(s) filedirectory
• Options
• -i run interactively, ask before overwriting
  files
• -f force copy, overwrite automatically
• mv file file_new
• ls -l file file_new
• ls file No such file or directory
• -rw-r--r-- 1 root root 4 Jul 23 2211 file_new

20

• ln creates a new link for a file
• Syntax
• ln options file link
• Options
• -s create a symbolic link
• -f force linking, overwrite automatically
• ln -s file file_new
• ls -l file file_new
• -rw-r--r-- 1 root root 5 Jul 23 2225 file
• lrwxrwxrwx 1 root root 4 Jul 23 2226 file_new -gt
  file

21

• rm removes a file or files list
• Syntax
• rm options file(s)
• Options
• -r recursively remove files and sub-directories
• -f force copy, overwrite automatically
• rm file_new
• ls -l file file_new
• ls file No such file or directory
• ls file_new No such file or directory

22

• mkdir create a new directory
• Syntax
• mkdir options directory
• Options
• -p create parent directories, if needed
• mkdir dir1
• ls -l
• drwxr-xr-x 2 root root 4096 Jul 23 2220 dir1
• Note mkdir is the only command from the above
  that can create a new directory. cp and mv
  will only copy existing directories with given
  -r

23
Thank You