Linux File System

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Linux File System

• Linux files and file systems
• Programs scripts and data are stored in the
  filesystem
• Unix is a file driven system-disk drives, tape
  drives, printers, swap files
• Files can be located on other network file
  systems
• Organized into logical directories
• Supports more then one file system

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File system

• File names can contain - Alpha characters(upper
  and lower)- punctunation marks numbers and
  symbols
• No limit to the number of extensions

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Directory Tree

• Organized into hierarchical structure

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Linux Directory tree

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Directories

• Working directory-the current place in the file
  systembashpwd ( prints working directory)
• The parent directory- bash .. Each directory
  (other then root) has a .. file.

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Important Directories

• /bin
• Short for binaries or executables. Notice that in
  this directory, you see cp, ls and mv and other
  utilities that we use as commands under shell.
  This directory is where executables.

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/DEV

• Contains device files. Contains system devices
  and resources like disk drives, etc. Just as the
  system can read data from a file, it can also
  read input from the mouse by accessing
  /dev/mouse.
• Filenames that begin with fd are floppy devices.
  Fs0 is the first floppy drive and fd1 is second.
• Also there are different variants of floppy
  devices that you should see. Fd1h1440 is high
  density 3.5 diskettes in drive 1.

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/DEV

• /dev /console refers to the systems consolethe
  monitor connected directly to the system.
• /dev/ttyS and /dev/cua devices are used for
  accessing serial ports.
• /dev/ttyS0 is equivalent to COM1 under MSDOS.
• /dev/cua devices are call out device and used
  with the modem.
• Device names beginning with hd are hard drives.
• /dev/had refers to the entire first hard disk.
• /dev/hda1 refers to the first partition on
  /dev/had.

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/DEV

• Device names that begin with sd are SCSI drives.
  If you have a SCSI drive, instead of accessing
  through a /dev/had, you would access /dev/sda.
• SCSI tapes are accessed via st devices.
• SCSI CD-ROM is accessed via sr devices.
• Device names that begin with lp accesses the
  parallel ports.
• /dev/lp0 is the same as LPT1 in DOS.

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/DEV

• /dev/null
• Is basically a black hole of the system. Any data
  sent to this device is gone forever.

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/USR

• Many items found in /usr are optional and used
  primarily for add-ons, extras installed in the
  system.
• /usr contains most of the larger software
  packages and the configuration files that
  accompany them.
• /usr/c11R6
• This is the directory that contains the X windows
  system if you have installed it. This directory
  contains all of the X windows executables,
  configuration files and support files.

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/USR

• /Usr/bin is the other warehouse of software on a
  Linux systems and contains most of the
  executables for the programs not found in other
  places like /bin.
• /usr/etc
• Just like the /etc contains essential
  miscellaneous system programs and configuration
  files, /usr/etc contains miscellaneous utilities
  and files that are in general are not essential
  to the system.

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/USR

• /usr/include
• Contains the include files for the C compiler.
• For C programmers, this is where youll find
  headers for files .h which declare functions.
• /usr/local
• Contains various programs and files not essential
  to the system but because of it makes your Linux
  different from other Linux systems.

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Redirecting input and output

• Redirection is when you redirect an output of a
  command to a file by using gt.
• Everyone make a file using

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Links

• Bash ln s filea new-linked-filea
• -every file has a number(inode) associated
  with it, a link
• -ln, allows files to be shared the same link
  with different names

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File security

• File security is important for Unix- multiple
  users on the system- control of network
  resources- control of device files- security of
  your own data
• User classes- owner- group- world

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Default File permissions

• Most unix systems will default to- file
  -rwxrwxrwx 111 111 111 777- default can
  be set using bash umask 022 000 010 010
  022

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Mode commands

• Bash chmod argument(s) list class - u user
  - g group - o other(world) operator
  - add - - deny - change all
  privileges - r read - w write - x
  execute

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Examples

• Allow r, w, x to every one on the system
  chmod ugo rwx file-name(s)
• Restrict w x for other users on the system
• chmod o - wx filename(s)