Basic Steps in Ubuntu 12.10

CLASSPATH SETTING IN UBUNTU

sudo gedit etc/environment

enter your password
PATH=".:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" (already exist)
just add below two lines 

here i am using java6

JAVA_HOME="/usr/lib/jvm/java-6-openjdk"

CLASSPATH=".:/usr/lib/jvm/java-6-openjdk/lib"

 Disable Guest Session and the Remote login in UBUNTU

To disable the guest session and/or remote logon in Ubuntu 12.10 (Quantal Quetzal):

1. Open a terminal window.
2. Type “sudo nano /etc/lightdm/lightdm.conf”
3. Type in your sudo password.
4. Add the following in a new line at the end of the file if you want to disable the guest session: allow-guest=false
5. Add the following in a new line at the end of the file if you want to disable the remote login option: greeter-show-remote-login=false
6. If you choose to disable both, your lightdm.conf file should probably look like this:
[SeatDefaults]
greeter-session=unity-greeter
user-session=ubuntu
allow-guest=false
greeter-show-remote-login=false

7. Hit CTRL-X to exit nano.
8. Hit Y to save the file.
9. Hit Enter to accept the original filename and overwrite the file.
10. On the terminal, type “sudo restart lightdm” to restart the display manager. Doing so will require you to log in again and may close running apps, so save your work before doing so.
11. The guest session and/or remote logon options should now be disabled.

UNIX Basic Commands

Files

• ls --- lists your files
  ls -l --- lists your files in 'long format', which contains lots of useful information, e.g. the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified.
  ls -a --- lists all files, including the ones whose filenames begin in a dot, which you do not always want to see.
  There are many more options, for example to list files by size, by date, recursively etc.
• more filename --- shows the first part of a file, just as much as will fit on one screen. Just hit the space bar to see more or q to quit. You can use /pattern to search for a pattern.
• emacs filename --- is an editor that lets you create and edit a file. 
• mv filename1 filename2 --- moves a file (i.e. gives it a different name, or moves it into a different directory (see below)
• cp filename1 filename2 --- copies a file
• rm filename --- removes a file. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. You can make this your default by making an alias in your .cshrc file.
• diff filename1 filename2 --- compares files, and shows where they differ
• wc filename --- tells you how many lines, words, and characters there are in a file
• chmod options filename --- lets you change the read, write, and execute permissions on your files. The default is that only you can look at them and change them, but you may sometimes want to change these permissions. For example, chmod o+r filename will make the file readable for everyone, and chmod o-rfilename will make it unreadable for others again. Note that for someone to be able to actually look at the file the directories it is in need to be at least executable.
• File Compression
  • gzip filename --- compresses files, so that they take up much less space. Usually text files compress to about half their original size, but it depends very much on the size of the file and the nature of the contents. There are other tools for this purpose, too (e.g. compress), but gzip usually gives the highest compression rate. Gzip produces files with the ending '.gz' appended to the original filename.
  • gunzip filename --- uncompresses files compressed by gzip.
  • gzcat filename --- lets you look at a gzipped file without actually having to gunzip it (same as gunzip -c). You can even print it directly, using gzcatfilename | lpr
• printing
• lpr filename --- print. Use the -P option to specify the printer name if you want to use a printer other than your default printer. For example, if you want to print double-sided, use 'lpr -Pvalkyr-d', or if you're at CSLI, you may want to use 'lpr -Pcord115-d'. See 'help printers' for more information about printers and their locations.
• lpq --- check out the printer queue, e.g. to get the number needed for removal, or to see how many other files will be printed before yours will come out
• lprm jobnumber --- remove something from the printer queue. You can find the job number by using lpq. Theoretically you also have to specify a printer name, but this isn't necessary as long as you use your default printer in the department.
• genscript --- converts plain text files into postscript for printing, and gives you some options for formatting. Consider making an alias like alias ecop 'genscript -2 -r \!* | lpr -h -Pvalkyr' to print two pages on one piece of paper.
• dvips filename --- print .dvi files (i.e. files produced by LaTeX). You can use dviselect to print only selected pages.

Directories

Directories, like folders on a Macintosh, are used to group files together in a hierarchical structure.

• mkdir dirname --- make a new directory
• cd dirname --- change directory. You basically 'go' to another directory, and you will see the files in that directory when you do 'ls'. You always start out in your 'home directory', and you can get back there by typing 'cd' without arguments. 'cd ..' will get you one level up from your current position. You don't have to walk along step by step - you can make big leaps or avoid walking around by specifying pathnames.
• pwd --- tells you where you currently are.

Finding things

• ff --- find files anywhere on the system. This can be extremely useful if you've forgotten in which directory you put a file, but do remember the name. In fact, if you use ff -p you don't even need the full name, just the beginning. This can also be useful for finding other things on the system, e.g. documentation.
• grep string filename(s) --- looks for the string in the files. This can be useful a lot of purposes, e.g. finding the right file among many, figuring out which is the right version of something, and even doing serious corpus work. grep comes in several varieties (grep, egrep, and fgrep) and has a lot of very flexible options. Check out the man pages if this sounds good to you.