End User and Sysadmin Basics commands

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End User and Sysadmin Basics commands
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Shells

• Shell software providing a user interface
• A shell provides access to services provided by
  the kernel related to the term kernel
• Two main types of shells
• Graphical
• Command line interface (CLI)

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Shells

• GUI Shells
• KDE
• Gnome
• CLI Shells
• sh, csh, ksh, zsh and tcsh
• bash (GNU) Bourne again shell
• fish Friendly and Interactive Shell
• Windows Shells
• Windows Explorer
• msh Microsoft Shell monad

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Some Bash Features

• Incorporates features from the Korn and C shells
• Command line editing
• Unlimited size command history
• Job Control
• Shell builtins (cd, pwd, alias, echo)
• Some builtins inherited from the Bourne shell
• Some builtins have been added to or improved upon
  in bash

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Shell Shortcuts

• match 0 or more characters
• ? match one character
• home directory of current user
• user home directory of user

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Files and directories

• File - an object that contains data.
• Different types of files exist (regular,
  directories, links)
• Regular files have no restrictions on content
  they just contain bits
• Inode a data structure containing information
  about files (ownership, permissions, type,
  timestamps, pointers to data blocks)
• The system refers to files not by name but by
  inode.

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Files and directories

• Directory an object used to organize files
• A special kind of file that contains a list of
  the files it contains
• A files name is stored in its parent directory,
  not the file itself.
• Special directory entries . and .. Can not
  be removed

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Files and directories

• Links pointers to another place
• Symbolic links a small file that redirects to
  another file
• Hard links associating several names with a
  single inode. (hard linked files look like two
  separate files, but actually point to the same
  bits on the disk)

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File system

• Hierarchical
• Types of file systems
• ext2, ext3 (extended file system)
• ReiserFS (was SuSEs default FS)
• FHS Filesystem Hierarchy Standard
• http//en.wikipedia.org/wiki/Filesystem_Hierarchy_
  Standard
• Special directories Everything is a file
• /dev
• /proc (procfs)

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Users and groups

• User a person who uses a system.
• User account the foundation of security, a
  means of identifying users on a system
• Group a grouping of users sharing a common need
• Group account method used to group user
  accounts on a system

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Permissions

• The ability to control what resources users (or
  groups of users) can access.
• Different permission paradigms exist
• No permissions DOS, Win9x, MacOS9
• Simple permissions default in UNIX/Linux
• ACLs Windows NT, 2K, XP, 2K3, optional in
  UNIX/Linux

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UNIX - Permissions

• Every file is owned by a user
• Every file is assigned a group
• Three permissions classes User Group and
  Others UGO
• Only an owner and the super user can change
  permissions

File Types - Regular file d Directory l
link
Link Count
Other
Modify date
Group
Inode
Owner
Group
Site in bytes
filename
User
File Type
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Getting Help

• man
• info
• --help or h
• tldp the Linux documentation project
• Wikipedia

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Man Page Convention

• Square Brackets and optional
• dot dot dot can be repeated
• Curly braces and Select one value,
  separated by
• ls OPTION... FILE...
• mkdir OPTION DIRECTORY...
• tail -F -f -r -b number -c number -n
  number file ...

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man page sections

• man pages are organized in sections
• Example fstab(5)

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man page navigation

• ???? Scroll man page
• /expression search for expression above
• ?expression search for expression below
• n find next
• q quit

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Your 1st commands

• whoami print effective userid
• whoami OTPTION
• cal displays a calendar
• cal -smjy13 month year
• date print or set the system date and time
• date OPTION FORMAT

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ls list directory contents

• ls OPTION FILE
• Interesting ls options
• -a dont hide hidden files
• -d show directory, not contents
• -h human readable sizes
• -i show inode number
• -l long list

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pwd print name of current/working directory

• pwd OPTION
• Only options are --help and --version

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cd change directory

• A bash builtin
• Allows navigation from working directory to
  another
• Special options
• . present directory
• .. parent directory
• current users home directory
• username usernames home directory
• - directory flip/flop

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touch change file timestamps

• touch OPTION... FILE...
• Good as a method for creating regular files
• Better as a method for testing to see if you have
  permissions to access a given file
• -t STAMP option set timestamp to value other
  than current time

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mkdir make directories

• mkdir OPTION DIRECTORY...
• Interesting mkdir options
• -v verbose
• -p make parent directories, if they dont
  already exist

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rmdir - remove empty directories

• rmdir OPTION... DIRECTORY...
• Interesting mkdir options
• -p try to delete parent directories
• --ignore-fail-on-non-empty suppress errors on
  non-empty directories. Will not delete non-empty
  directory

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rm - remove files or directories

• rm OPTION... FILE...
• Interesting rm options
• -r recursive removal
• -f force removal, no promts
• rm rf a common method for deleting a directory.

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mv - move (rename) files

• mv OPTION... SOURCE DEST
• mv OPTION... SOURCE... DIRECTORY
• Can be used to move move or rename both files or
  a directories
• Inodes are preserved

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cp - copy files and directories

• cp OPTION... SOURCE DEST
• cp OPTION... SOURCE... DIRECTORY
• Can be used to copy files and direcories
• Copied files get different inodes
• Interesitng cp options
• -r recursive
• -v verbose

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ln - make links between files

• ln OPTION... TARGET LINK_NAME
• Memory aid ln syntax mirrors cp
• Use full paths!
• -s symbolic or soft links
• Without -s link will be a hard link

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find - search for files in a directory hierarchy

• find path... expression
• The find command is very comprehensive, with a
  huge amount of options
• Some (of many) interesting options
• -name pattern search for files with a
  specific name (note a wildcard needs to be
  escaped! i.e. \)
• -inum n search for files with a specific
  inode number, n

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slocate - Security Enhanced version of the GNU
Locate

• Search for files in a database as opposed to the
  actual filsystem
• locate is linked to slocoate
• Interesting slocate/locate options
• -u update database, start at /
• -i case insensitive search

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df - report filesystem disk space usage

• df OPTION... FILE...
• Shows disk space available
• Shows where current directory is mounted
• Interesting options
• -h human readable
• -T show type of filesystem
• df alone will show free space on all filesystems

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du - estimate file space usage

• du OPTION... FILE...
• See how much space your files are consuming
• Interesting du options
• -h human readable
• -s summarize (i.e. dont show every file)

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chown - change file owner and group

• chown OPTION... OWNERGROUP FILE...
• Interesting chown options
• -R recursive
• chgrp can be used alternatively

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chmod - change file access permissions

• chmod OPTION... MODE,MODE... FILE...
• Examples
• chmod ux,gw,gw foo
• chmod 644 foo
• Octal notation shortcut

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Homework

• Check out the FHS http//www.pathname.com/fhs/
• Check out the Bash Reference Manual
  http//www.gnu.org/software/bash/manual/bashref.ht
  ml