Shell procedures

Shell procedures

From Steve Parker

The shell may be used to read and execute commands contained in a file. For example,

	sh file [ args ... ]

calls the shell to read commands from file. Such a file is called a command procedure or shell procedure. Arguments may be supplied with the call and are referred to in file using the positional parameters $1, $2, .... For example, if the file wg contains

	who | grep $1

then

	sh wg fred

is equivalent to

	who | grep fred

Linux Cheat Sheet

alias
Create an alias

Usage	alias [name[=’value’]]
Example	alias la=’ls -la --color=auto’
Explanation	Creates an alias for the ls command which displays a detailed list with various file types in different colours.
Windows equivalent	N/A

cat
Display the contents of a file

Usage	cat [options] [file1] [file2] ...
Example	cat index.html
Explanation	Displays the contents of the index.html file.
Windows equivalent	type

cd
Change directory

Usage	cd [-LP] [directory]
Example	cd /usr/local/bin
Explanation	Changes the /usr/local/bin directory.
Windows equivalent	cd

chgrp
Change group ownership

Usage	chgrp [options] group file1 file2 ...
Example	chgrp apache index.html
Explanation	Changes the group ownership of the index.html file to the apache group.
Windows equivalent	N/A

chmod
Change access permissions

Usage	chmod [options] mode file1 file2 ...
Example	chmod 755 script.cgi
Explanation	"Changes the permissions of script.cgi so that everyone can execute and read it
Windows equivalent	but only the owner can write to it."

chown
Change file owner and group

Usage	chown [options] new-owner file1 file2 ...
Example	chown root index.html
Explanation	Changes the ownership of the index.html file to root.
Windows equivalent	N/A

cmp
Character-by-character compare between two files

Usage	cmp [options] from-file to-file
Example	cmp index.html default.htm
Explanation	"Compares each character in index.html and default.htm
Windows equivalent	and displays the differences."

cp
Copy one or more files to another location

Usage	cp [options] source destination
Example	cp index.html index.html.bak
Explanation	Makes a second copy of the index.html file in the same directory. The new copy has the BAK extension.
Windows equivalent	"copy

df
Display free disk space

Usage	df [options] [file]
Example	df
Explanation	Displays the used and free disk space on all mounted filesystems.
Windows equivalent	dir

du
Estimate file space usage

Usage	du [options] [file]
Example	du
Explanation	Displays the disk usage of the current directory.
Windows equivalent	dir

echo
Display message on screen

Usage	echo [options] [string]
Example	echo Hello World!
Explanation	Displays the Hello World! message on the screen.
Windows equivalent	echo

env
"Display

Usage	set or remove environment variables"
Example	env [options] [name[=value]] [comand [args]]
Explanation	env HOME=/home/username
Windows equivalent	Changes the HOME environment variable to /home/username.

exit
Exit the shell

Usage	exit
Example	exit
Explanation	Exits from the current shell.
Windows equivalent	N/A

free
Display memory usage

Usage	free [options]
Example	free -s 5
Explanation	"Displays current memory usage
Windows equivalent	updating it every five seconds."

fsck
Filesystem consistency check and repair

Usage	fsck [options] [filesystem]
Example	fsck /dev/hda1
Explanation	Performs a filesystem check on the first partition of the primary master IDE drive.
Windows equivalent	chkdsk

grep
Search file(s) for lines that match a given pattern

Usage	grep [options] string [file1] [file2] ...
Example	"grep ""search string"" /home/*"
Explanation	"Searches all files in /home for the occurence of the ""search string""."
Windows equivalent	N/A

gzip
Compress or decompress named file(s)

Usage	gzip [options] file
Example	gzip index.html
Explanation	Compressed index.html into a file named index.html.gz.
Windows equivalent	N/A

kill
Stop a process from running

Usage	kill [options] pid
Example	kill 1234
Explanation	Terminates the process with id 1234. Use ps to determine a processes id.
Windows equivalent	kill

less
Display content one screen at a time

Usage	less [options]
Example	cat index.html | less
Explanation	"Displays the index.html file on the screen
Windows equivalent	one screen at a time."

ln
Make links between files

Usage	ln [options] target [linkname]
Example	ln -s /var/www/html /home/user/website
Explanation	Creates a shortcut named website from the user’s home directory to the /var/www/html directory.
Windows equivalent	shortcut

locate
Find files

Usage	locate [options] string
Example	locate perl
Explanation	Searches filesystem databases for files containing the term perl.
Windows equivalent	dir /s

ls
List information about file(s)

Usage	ls [options] [file/directory]
Example	ls -la /var/www/html
Explanation	Prints a detailed list of all files and directories located in the /var/www/html directory.
Windows equivalent	N/A

man
Help manual

Usage	man [options] [command]
Example	man man
Explanation	Displays the manual for the man command.
Windows equivalent	N/A

mkdir
Create new folder(s)

Usage	mkdir [options] directory
Example	mkdir html
Explanation	Creates a directory named html under the current directory.
Windows equivalent	md

mount
Mount a file system

Usage	mount [options] [device/directory]
Example	mount cdrom
Explanation	Mounts the CD-ROM drive.
Windows equivalent	N/A

mv
Move or rename files or directories

Usage	mv [options] source destination
Example	mv index.html /var/www/html
Explanation	Moves the index.html file from the current directory to /var/www/html.
Windows equivalent	move

nice
Set the priority of a command or job

Usage	nice [options] [comand [args]]
Example	nice -n 19 httpd
Explanation	Runs the httpd process with the lowest possible priority (-20 is the highest priority).
Windows equivalent	N/A

passwd
Modify a user password

Usage	passwd [options]
Example	passwd
Explanation	Prompts you to change the password for the current user. It will prompt for the old password first.
Windows equivalent	N/A

ping
Sends and echo packet to a host

Usage	ping [options] host
Example	ping www.apcmag.com
Explanation	Continually sends echo packets to the www.apcmag.com host.
Windows equivalent	ping

ps
Process status

Usage	ps [options]
Example	ps -ef
Explanation	Displays full list of all running processes.
Windows equivalent	mem

pwd
Print working directory

Usage	pwd [options]
Example	pwd
Explanation	Prints the directory the terminal is presently in.
Windows equivalent	cd

rm
Remove files

Usage	rm [options] file1 file 2 ...
Example	rm -rf /var/www/html
Explanation	Forces the removal of the /var/www/html directory and all files and subdirectories indside it.
Windows equivalent	del

rmdir
Remove folder(s)

Usage	rmdir [options] directory1 directory2 ...
Example	rmdir /var/www/html
Explanation	Removes the /var/www/html directory (assuming it’s empty).
Windows equivalent	rd

shutdown
Shutdown or restart Linux

Usage	shutdown [options] when [message]
Example	shutdown -r 20:00
Explanation	Reboots the system at 8pm.
Windows equivalent	shutdown

sleep
Delay for a specified time

Usage	sleep [number]
Example	sleep 30
Explanation	Pauses for 30 seconds — useful in some scripts.
Windows equivalent	sleep

su
Substitute user identity

Usage	su [options] [username [args]]
Example	su
Explanation	Switches to the root user.
Windows equivalent	"su

tail
Output the last part of files

Usage	tail [options] [file1] [file2] ...
Example	tail /var/log/error.log
Explanation	Displays the last 10 lines of the error log.
Windows equivalent	N/A

tar
Tape archiver

Usage	tar [options] file1 [file2] ...
Example	tar - czvf archive.tar.gz /var/www/html
Explanation	Compresses the contents of the /var/www/html directory into a gzipped tarball named archive.tar.gz.
Windows equivalent	N/A

touch
Change file timestamps

Usage	touch [options] file1 ...
Example	touch /var/www/html/index.html
Explanation	"Updates the timestamp on /var/www/html/index.html
Windows equivalent	or creates the file if it doesn’t exist."

top
List processes running on the system

Usage	top [options]
Example	top
Explanation	Provides an automatically-updating list of the most CPU intensive processes running on the system.
Windows equivalent	N/A

traceroute
Trace route to host

Usage	traceroute [options] host [packetsize]
Example	traceroute www.apcmag.com
Explanation	Prints a list of all routers (and IP addresses) that IP datagrams pass through en route to the www.apcmag.com server.
Windows equivalent	tracert

umount
Unmount a device

Usage	umount [options] [device/directory]
Example	umount cdrom
Explanation	Unmounts the CD-ROM drive.
Windows equivalent	N/A

unalias
Remove an alias

Usage	unalias [options] [name]
Example	unalias la
Explanation	Removes the alias named la.
Windows equivalent	N/A

uname
Print system information

Usage	uname [options]
Example	uname -a
Explanation	Prints all system information relating to the machine and OS.
Windows equivalent	N/A

which
Locate a program file in the user’s path

Usage	which [options] file ...
Example	which perl
Explanation	"Same as locate
Windows equivalent	but restricts the search to the user’s path."

POSIX version affects Coreutils

1) http://lists.debian.org/debian-glibc/2003/08/msg00127.html
This has some information about the sort & tail.
2) http://linux.com.hk/PenguinWeb/manpage.jsp?name=sysconf&section=3
This has information on the System Environment Variables
3) http://www.sunsite.ualberta.ca/Documentation/Gnu/gawk-3.0.6/html_node/gawk_136.html#IDX513
This is quite long, about GNU which relates to POSIX variable.

Mounting of Floppy on SUN Solaris

1) volcheck - equivalent to mount in Linux
2) By default, mount point is /floppy
3) eject - equivalent to umount in Linux

Very useful site from SUN

SSH Configuration

Possible Steps to Check the Configuration
1) ssh -v -v -v
To increase the verbosiy, some vs will take ssh -vvv
2) pgrep sshd
To make sure the daemon/server service is running if it return a process ID
3) /etc/ssh/sshd_config
To determine which port is in use for the ssh communication
4) Make link between ~/.ssh/authorized_keys to ~/.ssh/authorized_keys2
To ensure both protocol will grap the keys either way (SSH has 2 protocol, 1 & 2)
5) Trying "cat"ing the key instead of "cp"ing the keys as the later might change the format.

More info from www.linuxquestions.org

Installation of NIC driver onto Dell PowerEdge W/S

From Intel Website

Steps can be found from README pages.

To allow rsh

If you must use rexec, rsh, and rlogin, and if you need to use them as root, you will need to make a few modifications to the /etc/securetty file. All three of these tools have PAM configuration files that require the pam_securetty.so PAM module, so you must edit /etc/securetty to allow root access.

Before you can log in as root using these tools, you first have to have them properly set up. First, install the rsh-server RPM, which is included with Red Hat Linux 7.1. See the Official Red Hat Linux Customization Guide if you need assistance using RPM.

Next, run ntsysv and enable rexec, rsh, and rlogin. See the ntsysv man page if you need help using this tool.
Finally, restart xinetd with /sbin/service xinetd restart to activate the ntsysv changes. At this point, all users except root will be able to use rexec, rsh, and rlogin.

To allow root to use these tools, add the names of the tools you wish to allow to the /etc/securetty. If you wanted to enable root login using rexec, rsh, and rlogin, add the following lines to /etc/securetty:

rexec
rsh
rlogin

To allow root to log in using these tools via telnet (an even worse idea but necessary in some environments), add a few more lines:

pts/0
pts/1

Info from Redhat