Transcript Linux Files and Directories - INASP

Linux Files and Directories
Linux
directories
• Linux system is arranged in
what is called a hierarchical
directory structure. This
means that they are
organized in a tree-like
pattern of directories (called
folders in other systems),
which may contain files and
other directories. The first
directory in the file system
is called the root directory.
Understanding Linux directories
• Ubuntu uses the Linux file system, which is
based on a series of folders in the root
directory. Each of these folders contains
important system files that cannot be modified
unless you are running as the root user or
use sudo.
• This restriction exists for both security and
safety reasons: computer viruses will not be
able to change the core system files, and
ordinary users should not be able to
accidentally damage anything vital.
Linux directories
Below are some of the most important directories.
• The root directory—denoted by /—contains all other
directories and files.
Here are the contents of some essential system
directories:
• /bin & /sbin Many essential system applications
(equivalent to C:\Windows)
• /etc System-wide configuration files
• /home Each user will have a subdirectory to store
personal files (for example
• /home/your-username, equivalent to C:\Users or
C:\Documents and Settings)
• /lib Library files, similar to .dll files on Windows
Linux directories
• /media Removable media (CD-ROMs &
USB drives) will be mounted in this directory
• /root contains the root user’s files (not to be
confused with the root directory)
• /usr Pronounced “user,” it contains most
program files (not to be confused with each
user’s home directory, equivalent to
C:\Program Files)
• /var/log Contains log files written by many
applications
Understanding Linux directories
• Think of the file system tree as a maze, and you are standing in it. At any
given moment, you are located in a single directory.
– Inside that directory, you can see its files and the pathway to its parent
directory and the pathways to the subdirectories of the directory in
which you are standing.
• The directory you are standing in is called the working directory.
• To find the name of the working directory, use the pwd command.
– me@linuxbox$ pwd
/home/me
• When you first log on to a Linux system, the working directory is set to
your home directory. This is where you put your files.
– On most systems, your home directory will be called
/home/your_user_name
Looking around using LS
• The ls command is used to list
the contents of a directory. It is
probably the most commonly
used Linux command. It can be
used in a number of different
ways.
Closer look at LS command
• If you use the -l option with ls, i.e. (ls –
l) you will get a file listing that contains a
wealth of information about the files
being listed (see next slide)
Using command ls -l
Interpreting results of ls -l
• File Name: The name of the file or directory.
• Modification Time: The last time the file was modified. If the
last modification occurred more than six months in the past, the
date and year are displayed. Otherwise, the time of day is
shown.
• Size: The size of the file in bytes.
• Group: The name of the group that has file permissions in
addition to the file's owner.
• Owner: The name of the user who owns the file.
• File Permissions: A representation of the file's access
permissions. The first character is the type of file. A "-"
indicates a regular (ordinary) file. A "d" indicates a directory.
The second set of three characters represent the read, write,
and execution rights of the file's owner. The next three
represent the rights of the file's group, and the final three
represent the rights granted to everybody else.
Some ls options
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-a or --all Displays hidden files as well
-i or --inode Displays the unique file number (inode number)
-l or --format=long Displays extra information
-o or --no-color Omits colour-coding the output
-p or -F Marks file type by adding a special character
-r or --reverse Reverses sort order
-R or --recursive Recurses into subdirectories (DOS: DIR/S)
-S or --sort=size Sorts files by size (longest first)
-t or --sort=time Sorts file by modification time (newest first)
-X or --sort=extension Sorts file by extension (“file type”)
Important facts about file names
• File names that begin with a period character are hidden.
– This only means that ls will not list them unless you say ls -a.
• File names in Linux, like Unix, are case sensitive. The file names
"File1" and "file1" refer to different files.
• Linux has no concept of a "file extension" like legacy operating
systems.
• Though Linux supports long file names which may contain
embedded spaces and punctuation characters, limit the
punctuation characters to period, dash, and underscore.
– Most importantly, do not embed spaces in file names. If
you want to represent spaces between words in a file name,
use underscore characters. You will thank yourself later.
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18/07/2015
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