Lab Exercise 2

create a "command" then use chmod, chown and continue working with other Real World commands

 create a command - use chmod, chown, which, locate, cnf, zypper, cat, echo and command

Script started on Mon 08 Dec 2014 12:21:15 AM PST

Open a Linux or Cygwin Session and 
	type the items after the "-->"  
	(if your output differs then try to figure out why)
-----------------------------------------------

--> mkdir LAB; cd LAB
 
--> echo "this is a command" 

		you should see:     this is a command

--> echo "this is a command" > tstcmd

--> cat tstcmd
this is a command

	If you were to execute "tstcmd" would it do the same thing as the command line above?
	In order for it to actually print out the statement, the file tstcmd will need to include the echo and quotes.

		the echo command is the executable part of tstcmd to produce the statement.

----------------------------------------------------------------------------
to include the entire string, try:

--> echo "echo \"this is a command\"" > tstcmd

	the \ escapes the shell's understanding of the special character " and allows it to be echoed instead of executed

now look at the file again:
 
--> cat tstcmd
echo "this is a command"

		now the file will produce the statement "this is a command" if executed

----------------------------------------------------------------------------
ATTEMPTING TO "RUN" this new program or command called tstcmd.

	if you type "tstcmd" at the prompt, what happens?

--> tstcmd
bash: /home/john/tstcmd: Permission denied

	what does Permission denied mean?

	try it again telling the shell to run it here...

------------------------------------------------
--> sh ./tstcmd
this is a command

	that worked... 

	let's try using command, which ignores the shell functions that we just used.
 
------------------------------------------------
--> command tstcmd
bash: /home/john/tstcmd: Permission denied

	what does Permission denied mean?   here it is again

	we've created a program that echoes a string, but it's not working.  
	We mentioned the which command before to tell us where a command was located.
	
------------------------------------------------
--> which tstcmd
which: no tstcmd in (/home/john/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr...
 
	which doesn't find it...

	examining our environment variables, let's look at our path statement:

--> env | grep -i path
MANPATH=/usr/local/man:/usr/share/man
XNLSPATH=/usr/share/X11/nls
PATH=/home/john/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/usr/bin/:/...
ALSA_CONFIG_PATH=/etc/alsa-pulse.conf
WINDOWPATH=7
QT_PLUGIN_PATH=/home/john/.kde4/lib64/kde4/plugins/:/usr/lib64/kde4/plugins/

	the . is in our path but it didn't find it.
	we also see other items in our grep... we could clean this up with the following command now that we know the PATH variable is uppercase:

------------------------------------------------
--> env | grep ^PATH= 
PATH=/home/john/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/usr/bin/:/home/john/bin:/...

	the up caret before PATH and the equal sign after help clearly identify the pattern we're searching for.     
	The truncated path statement has redundancies, we'll address how to deal with that in a later session.	

	which didn't find it, how about "locate"
	
------------------------------------------------
--> locate tstcmd 
If 'locate' is not a typo you can use command-not-found to lookup the package that contains it, like this:
    cnf locate


	locate is not loaded on SuSe by default, the error message gives us a hint.     using sudo we can install it:

------------------------------------------------
--> sudo cnf locate 
                      
The program 'locate' can be found in following packages:
  * mlocate [ path: /usr/bin/locate, repository: zypp (openSUSE-13.2-0) ]
  * mlocate [ path: /usr/bin/locate, repository: zypp (repo-oss) ]

Try installing with:
    zypper install mlocate

------------------------------------------------
--> zypper install mlocate
Root privileges are required for installing or uninstalling packages.

------------------------------------------------
--> sudo zypper install mlocate
Retrieving repository 'openSUSE-13.2-Update' metadata ......................................................................[done]
Building repository 'openSUSE-13.2-Update' cache ...........................................................................[done]
Loading repository data...
Reading installed packages...
Resolving package dependencies...

The following 2 NEW packages are going to be installed:
  mlocate mlocate-lang 

The following recommended package was automatically selected:
  mlocate-lang 

2 new packages to install.
Overall download size: 111.7 KiB. Already cached: 0 B  After the operation, additional 389.3 KiB will be used.
Continue? [y/n/? shows all options] (y): y
Retrieving package mlocate-0.26-15.1.2.x86_64                                                (1/2),  62.9 KiB (143.3 KiB unpacked)
Retrieving: mlocate-0.26-15.1.2.x86_64.rpm .................................................................................[done]
Retrieving package mlocate-lang-0.26-15.1.2.noarch                                           (2/2),  48.8 KiB (246.0 KiB unpacked)
Retrieving: mlocate-lang-0.26-15.1.2.noarch.rpm ............................................................................[done]
Checking for file conflicts: ...............................................................................................[done]
(1/2) Installing: mlocate-0.26-15.1.2 ......................................................................................[done]
Additional rpm output:
Updating /etc/sysconfig/locate...


(2/2) Installing: mlocate-lang-0.26-15.1.2 .................................................................................[done]

------------------------------------------------
--> locate tstcmd
locate: can not stat () `/var/lib/mlocate/mlocate.db': No such file or directory

------------------------------------------------
--> tstcmd
bash: /home/john/tstcmd: Permission denied
	
	clearly we can not execute this file as configured.

	Maybe, the file needs to be owned by root, since we're seeing a Permission denied error

--> chown root tstcmd
chown: changing ownership of ‘tstcmd’: Operation not permitted

------------------------------------------------
--> sudo chown root tstcmd

------------------------------------------------
--> ls -l tstcmd
-rw-r--r-- 1 root users 25 Dec  8 00:23 tstcmd

------------------------------------------------
--> tstcmd
bash: /home/john/tstcmd: Permission denied

------------------------------------------------
--> sudo chown john tstcmd

	changing ownership back to john

------------------------------------------------
--> ls -l tstcmd
-rw-r--r-- 1 john users 25 Dec  8 00:23 tstcmd
------------------------------------------------

	so after all that, and it still will not execute as a command unless we invoke it from the shell.

	we briefly talked about how file permissions had a bearing on which, locate and command and how the file needs to be executable.
 
------------------------------------------------
--> ls -al tstcmd

-rw-r--r-- 1 john users 18 Dec	8 00:21 tstcmd

	the file tstcmd has the following permissions:

		owner:   read  write  - 
			  4     2     1      
		group:   read   -    -
		other:   read  -    - 

	the numeric value for this is 644, where 4+2 =6 or read + write = 6

	let's try some changes and see what happens to the file and if it executes

------------------------------------------------
--> chmod u+x tstcmd
 
------------------------------------------------
--> ls -al tstcmd
-rwxr--r-- 1 john users 25 Dec	8 00:23 tstcmd
 
------------------------------------------------
--> which tstcmd
/home/john/tstcmd
 
------------------------------------------------
--> tstcmd
this is a command
 
------------------------------------------------
--> chmod 755 tstcmd
 
------------------------------------------------
--> ls -al tstcmd
-rwxr-xr-x 1 john users 25 Dec	8 00:23 tstcmd
 
------------------------------------------------
--> chmod o-x tstcmd
 
------------------------------------------------
--> tstcmd
this is a command

------------------------------------------------
--> ls -al tstcmd
-rwxr-xr-- 1 john users 25 Dec	8 00:23 tstcmd
 
------------------------------------------------
--> chmod g-x tstcmd
------------------------------------------------
--> ls -l tstcmd
-rwxr--r-- 1 john users 25 Dec	8 00:23 tstcmd
 
------------------------------------------------
--> chmod 706 tstcmd
------------------------------------------------
--> ls -l tstcmd
-rwx---rw- 1 john users 25 Dec	8 00:23 tstcmd
 
------------------------------------------------
--> chmod 705 tstcmd
 
------------------------------------------------
--> ls -l tstcmd
-rwx---r-x 1 john users 25 Dec	8 00:23 tstcmd
 
------------------------------------------------
--> chmod 755 tstcmd
 
------------------------------------------------
--> ls -al tstcmd
-rwxr-xr-x 1 john users 25 Dec	8 00:23 tstcmd

	so we've seen that in order for a command to execute without using the shell function we need to make it executable
	with the chmod command.  The chown command changed ownership but did not allow it to execute unless the x bit was set.

LINUX Commands - real world

	for the following commands type the example provided, or execute man  and look at the options, or type the command with --help
	each of these commands has a real world use, or is of importance - if an example is not provided it'll be listed with (not used very often).

==============================================================================
  alias    Create an alias •
	alias froglegs="ls -aRlt | more"
  awk      Find and Replace text, database sort/validate/index
	awk -F: '($3 == "0") {print}' /etc/passwd
==============================================================================
  bash     GNU Bourne-Again SHell 
	no example needed
  bg       Send to background
	this is used after using ^Z (ctrl Z) to halt a program, and then put in the background
==============================================================================
  cal      Display a calendar
	cal -3  ; cal 1974
  cat      Concatenate and print (display) the content of files
	cat /etc/passwd
  cd       Change Directory
	cd /usr/bin ; cd
  chmod    Change access permissions
	touch TESTTHIS ; chmod 777 ; ls -l TESTTHIS ; chmod (make up a number and look at the file)
  chown    Change file owner and group
	not used very often, example above
  chkconfig System services (runlevel)
	this is a sysadmin thing, try it, with and without sudo
  clear    Clear terminal screen
	clear
  cmp      Compare two files
	echo 1234 > file1 ; echo 123 > file2 ; cmp file1 file2
  command  Run a command - ignoring shell functions •
	shown above, rarely used
  cp       Copy one or more files to another location
	cp file2 file3
  cut      Divide a file into several parts
	not used very often, examples in scripts
==============================================================================
  date     Display or change the date & time
	date
  dd       Convert and copy a file, write disk headers, boot records
	this is an advanced command, do NOT attempt to use it
  df       Display free disk space
	df -h
  diff     Display the differences between two files
	diff file1 file2
  dmesg    Print kernel & driver messages 
	dmesg | more   (   or if permission denied: )    sudo dmesg | more 
  du       Estimate file space usage
	du -sh /tmp
==============================================================================
  echo     Display message on screen •
	shown above
  eject    Eject removable media
	insert a CD or DVD then type eject
  env      Environment variables
	env | more  ; env | grep -i PS
  exit     Exit the shell
  export   Set an environment variable
	used in .bashrc
==============================================================================
  fdisk    Partition table manipulator for Linux
	fdisk -l     (didn't work? try: )  sudo fdisk -l
  fg       Send job to foreground 
	related to jobs and bg  not used much
  file     Determine file type
	file /etc/passwd ; file /usr/bin/ls
  find     Search for files that meet a desired criteria
	find /etc -type f -name passwd -print
  free     Display memory usage
	free
  fsck     File system consistency check and repair
	used on UNMOUNTED filesystems - advanced command don't use
  fuser    Identify/kill the process that is accessing a file
	advanced command, not used very often, but if you try to kill a proc and you can't, fuser tells who is using it
==============================================================================
  grep     Search file(s) for lines that match a given pattern
	grep PATH .bashrc
==============================================================================
  head     Output the first part of file(s)
	head .bashrc
  history  Command History
	history
  hostname Print or set system name
	hostname
==============================================================================
  ifconfig Configure a network interface
	/sbin/ifconfig -a
  ifdown   Stop a network interface 
	advanced command, don't attempt
  ifup     Start a network interface up
	advanced command, don't attempt
==============================================================================
  jobs     List active jobs •
	jobs    (nothing should show up... but try:  xeyes & ; jobs
==============================================================================
  kill     Stop a process from running
	advanced... we'll cover later
  killall  Kill processes by name
	advanced... we'll cover later
==============================================================================
  less     Display output one screen at a time
	less is more
  ln -s    Create a symbolic link to a file
	ln -s .bashrc MYBASHRC ; ls -al
  locate   Find files
	locate ls
  ls       List information about file(s) (ls -al)
	ls -alR /
  lsof     List open files
	lsof
==============================================================================
  man      Help manual
	man man
  mkdir    Create new folder(s)
	mkdir bin
  more     Display output one screen at a time
	more is less
  mount    Mount a file system
	advanced we'll cover later
  mv       Move or rename files or directories
	mv MYBASHRC CopyofBashrc
==============================================================================
  netstat  Networking information
	netstat -a  
  nice     Set the priority of a command or job
	DO NOT USE THIS COMMAND - very advanced... can crash the system
  nohup    Run a command immune to hangups
	not used very often - keeps command running if the session is disconnected, useful during dialup days
  nslookup Query Internet name servers interactively
	nslookup google.com (if you're behind a firewall may not work, try a known system on your network)
==============================================================================
o
==============================================================================
  passwd   Modify a user password
	use to change your passwd
  ping     Test a network connection
	ping (some device or server) (if you're behind a firewall or NAT you won't be able to hit outside IPs) (may need to use the -4 option)
  ps       Process status
	ps -ef | more
  pwd      Print Working Directory
	cd /etc/sysconfig ; pwd ; cd /tmp ; pwd ; cd ; pwd
==============================================================================
==============================================================================
  read     Read a line from standard input •
	used in scripts - advanced
  reboot   Reboot the system
	DO NOT DO THIS UNLESS YOU MEAN IT.  :)
  rm       Remove files
	touch nukethis ; rm nukethis (answer yes or say n and then:  rm -f nukethis
  rsync    Remote file copy (Synchronize file trees)
	we'll cover this soon... very nice, but complex tool
==============================================================================
  scp      Secure copy (remote file copy)
	we'll cover this later... very nice tool, but requires two systems;  
		scp file  someothersystem.xxx:/home/user/  or scp -r someothersystem.xxx:/home/user/dir .
  sed      Stream Editor
	see:  removing spaces and special characters
  shutdown Shutdown or restart linux
	DO NOT DO THIS UNLESS YOU MEAN IT.  :)
  sleep    Delay for a specified time
	date ; sleep 20 ; date
  sort     Sort text files
	cat /etc/passwd | tee -a passwd-notsorted ; sort /etc/passwd | tee -a passwd-sorted ; diff passwd-notsorted passwd-sorted
  ssh      Secure Shell client (remote login program)
	ssh someserver w
  su       Substitute user identity
	su - billybob
  sudo     Execute a command as another user
	sudo su -
==============================================================================
  tail     Output the last part of file
	tail /etc/passwd
  tar      Store, list or extract files in an archive
	tar cvf passwd.tar /etc/passd
  tee      Redirect output to multiple files
	cat /etc/passwd | tee -a passwd-notsorted ; sort /etc/passwd | tee -a passwd-sorted ; diff passwd-notsorted passwd-sorted
  test     Evaluate a conditional expression
	will cover later
  time     Measure Program running time
	time ls -alR /etc  (or / if you have time...)
  touch    Change file timestamps
	touch this-is-an-empty-file ; ls -al
  top      List processes running on the system
	top
  traceroute Trace Route to Host
	route ; trace route (gateway)
  tr       Translate, squeeze, and/or delete characters
	see:  removing spaces and special characters
==============================================================================
  ulimit   Limit user resources •
	ulimit
  umask    Users file creation mask
	umask
  umount   Unmount a device
	ONLY USE TO unmount a device... 
  unalias  Remove an alias •
	unalias froglegs
  uname    Print system information
	uname -a
  uniq     Uniquify files
	examples provided in lab 1
  uptime   Show uptime
	uptime ; w ; top
  useradd  Create new user account
	advanced sys admin task
  userdel  Delete a user account
	advanced sys admin task
  usermod  Modify user account
	advanced sys admin task
==============================================================================
  vi       Text Editor
	vi testthistool
  vmstat   Report virtual memory statistics
	vmstat
==============================================================================
  wc       Print byte, word, and line counts
	cat /etc/passwd | wc -l
  whereis  Search the user's $path, man pages and source files for a program
	whereis .bashrc
  which    Search the user's $path for a program file
	which ls
  while    Execute commands
	used in scripts
  who      Print all usernames currently logged in
	who
  whoami   Print the current user id and name (`id -un')
	whoami ; who am i
  wget     Retrieve web pages or files via HTTP, HTTPS or FTP
	wget http://someserver/somefile
==============================================================================
  xargs    Execute utility, passing constructed argument list(s)
	see find examples
==============================================================================
==============================================================================
  zip      Package and compress (archive) files.
==============================================================================
  .        Run a command script in the current shell
  !!       Run the last command again
  ###      Comment / Remark
============================================================================== 

Script done on Mon 08 Dec 2014 12:34:16 AM PST

================================================================================
    john meister, lab manager, mstm
  IT systems design and integration specialist  / Linux, UNIX and lesser OSes
================================================================================