Chapter 9 Part II Linux Command Line Access to Linux Authenticated login using a Linux account is...
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Transcript of Chapter 9 Part II Linux Command Line Access to Linux Authenticated login using a Linux account is...
![Page 1: Chapter 9 Part II Linux Command Line Access to Linux Authenticated login using a Linux account is required to access a Linux system. The Linux prompt will.](https://reader035.fdocuments.net/reader035/viewer/2022062217/56649e255503460f94b1426e/html5/thumbnails/1.jpg)
Chapter 9 Part II Linux Command Line
Access to Linux• Authenticated login using a Linux account is required to
access a Linux system. The Linux prompt will be shown only if the authentication information is correct.
• The Linux prompt includes the user name, followed by a @machine name. ( wpilkey@Linux:~# )
• The Linux command syntax is very basic, and starts with a Linux command separated by spaces, and followed by optional parameters and switches.– A switch changes the way a command runs.
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Basic Linux Skills and Concepts
• Comparing DOS and Linux – DOS is single user, single tasking– Linux is multi-user, multitasking– Many differences & Similarities in command-line interface
• The Shell– Character-mode user interface component– Processes commands– Issues error messages and other feedback – Called COMMAND.COM in DOS– Called BASH in Linux
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• Case Sensitivity– DOS is case insensitive– Linux is case sensitive– Designation of Switches – A switch changes the way a command runs– Switches in DOS begin with a slash (/)– Switches in Linux begin with a dash (-)
• Use of Spaces– DOS allows a space to be omitted between a command and a switch– Each part of a Linux command must be separated by a space – These commands will not work in Linux
– shutdown-h now – shutdown -hnow
Basic Linux Skills and Concepts
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• Paths– DOS and Windows
• Paths begin with a drive designator (C:)• A backslash (\) after the drive designator indicates the
root of that logical drive• Portions of path separated with backslashes
– Linux• No drive letter designation• Path begins with a slash (/) indicating the root• Portions of path separated with slashes• Example: /etc/gtk• Everything (devices, services, etc.) is a file
– /dev/sda0 (the first hard drive on a SCSI interface)– /dev/hda1 (the first hard drive on an IDE interface)
Basic Linux Skills and Concepts
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• Linux Feedback– DOS and Linux similar in providing cryptic feedback– No feedback when command is successful– Both provide error messages – Linux provides minimum output
• DOS dir command lists more information on files• Linux ls command (without switches) only shows file names
Basic Linux Skills and Concepts
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• The Command Syntax– command<space>option<space>option…– Options preceded by a - hyphen are switches– Multiple switches can be combined behind one hyphen– Another type of option is a parameter
• File name, directory, device name, or other.• Parameter at end of command
– Syntax: command –switch parameter– Example: ls –a /etc
Basic Linux Skills and Concepts
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• Command-Line History – Shell commands are saved during a session– Scroll through the commands at the $ prompt
• Up Arrow and Down Arrow
– Move within a command to edit it• Left Arrow and Right Arrow
– Press Enter to run command– Command history saved in the bash_history file
• Command Completion– A feature that completes a command line – Enter portion of a command and press the Tab key– Linux will try to guess the remaining portion
Basic Linux Skills and Concepts
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Shells, Terminals, and the Kernel
• Terminal– Channel that allows a certain user to log in and
communicate with the kernel via a user interface
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Shells, Terminals, and the Kernel
• Shell– User interface that accepts input from the user and
passes the input to the kernel for processing– Shell used by default in Linux is the BASH Shell
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The Linux Directory Structure• Is arranged hierarchically using a series of directories to
store files, and the location of these directories and files can be described using absolute or relative pathnames
Figure 4-2: The Linux filesystem structure
Linux
Windows
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DOS versus Linux • Case sensitivity – Linux is case-sensitive, DOS is Not.
• Switches – Linux switches start with a hyphen (-) while DOS switches start with a slash (/).
• Spaces – Linux command line must be separated by a space. DOS commands can work with or without a space
• Path - Linux uses the forward slash (/) to indicate a path to a folder, while DOS uses the backslash (\) character to indicate a path to a folder.
• Output – Linux provides only the minimum output while DOS provides a very descriptive output.
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Shell Metacharacters• Metacharacters: characters that help define other characters • Key combinations that have special meaning in the Linux
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Command Sampler
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Command Line
• The pwd command Print Working Directory - The default action is to show the current folder as an absolute path.
• The cd command Change Directory - change the current working directory to a specific Folder.
# cd /usr/local/sybase move to sybase folder
# pwd print current folder
/usr/local/sybase
# cd .. move up one folder
# pwd print current folder
/usr/local/
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File Permissions
Anatomy of ls –l output
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Listing the Contents of a Folder • The ls command is used to list the contents of a folder and
information about files, by default the current directory.• By default, the ls command only provides the names of
visible files in the current folder.• Some frequently used swicthes: -l, -a, -F
# ls –al
total 109drwxr-xr-x 18 root root 4096 Jun 9 21:12 ./drwxr-xr-x 18 root root 4096 Jun 9 21:12 ../drwxr-xr-x 2 root root 4096 Jun 9 21:14 bin/drwxr-xr-x 3 root root 1024 Jun 9 20:32 boot/drwxr-xr-x 6 root root 36864 Jul 12 10:26 dev/drwxr-xr-x 34 root root 4096 Jul 12 10:25 etc/drwxr-xr-x 5 root root 4096 Jun 9 21:28 home/
File type, permissions, hard link count, file owner, group owner, size, mod date, directory name, filename or pointer.
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Creating folders and Deleting in Linux
• The mkdir command Create new folder(s), if they do not already exist.
Create labdir directory underneath the current directory
# mkdir labdir
• The rmdir command Remove folder(s), if they are empty.
# rmdir labdir
• The ‘rm’ command is used for deleting files & folders• The command requires at least one parameter – the name
of the file to be deleted. Defaults to –i or interactive prompt
# rm filename
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Renaming or Moving Files in Linux• The mv command is used to rename a file or to move a
file from one folder to another. Defaults to –i or interactive prompt
• The command required two parameters – the name of the original file and the new name or location of the file.
Rename hosts file to hosts2, if hosts2 exists, you are prompted
# mv hosts hosts2
Force rename without prompting# mv –f hosts hosts2
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Copying Files in Linux • The cp command is used to copy one or more files to
another location. Can be used to do backups. Defaults to –i or interactive prompt
• The command requires two parameters – the source file and the destination where the file has to be copied.
Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY
copy home directory to floppy-f switch means remove existing destinations, never prompt # cp -f /mnt/floppy/* /home/simon
Copy file hosts from directory /etc to this directory “ .”# cp /etc/hosts .
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Displaying the Contents of a File • The cat command displays the entire contents of a file.# cat filename
• The more and less commands display the contents of a file one page at a time, ironically less provides more emulation and extensive enhancements, (moving, jumping, searching, line edit)
• The head command displays the first ten lines of a file.
• The tail command displays the last ten lines of a file.
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Logoff and Shutdown in Linux • The exit command or the CTRL-D key combination can be used to log out Linux
• The shutdown –h now command is used to shut down the Linux machine immediately, and halt after shutting down. Normally root can shut down Linux from command line– A Linux GUI will allow ordinary user to shutdown Select Log Out |
Shutdown– Root can enable/disable this feature in the GUI– shutdown –h now
• Linux shuts down and turns off the computer– shutdown –r now
• Linux shuts down and reboots the computer
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Basic Linux Skills and Concepts
• The Help Manual– Online manual accessed with man command– Syntax: man command
• Where command is the name of the command you wish to view
• Enter man man to see documentation for the man • Page Down & Page Up to scroll one screen at a time• Up Arrow and Down Arrow to scroll one line at a time
– man shutdown• The man command will display the complete
list of switches for the shutdown command
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The Filesystem Hierarchy Standard (FHS)
Table 5-1: Linux directories defined by FHS