Just type the command as follows:

gconf-editor

Expand the tree menu and locate in the node apps/nautilus/destop.Then set the value of ’volumes_visable‘ to the false.

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How to use the  shell command to count files in a directory (directory can have one or more subdirectories)?
And you want to output the results as follows:
(Can display the count of files in a directory)

17 ./test/dir1
12 ./test/dir2
16 ./test/dir3/dir4/dir5
15 ./test/dir3/dir4/dir6
23 ./test/dir3/dir4/dir7

Maybe you can use ls and wc command.But today I will introduce you a alternative way to reach this goal-Use find and uniq command.Maybe that is more easy to understand and clear to use，I think.

Let's check this command:


find . -type f -printf %h"\n" | sort | uniq -c

The first part of the command acually list the leading directories of all the files in current directory.Like the file "/usr/bin/yes" only shows its directory "/usr/bin"。That's controled by the -printf %h"\n" option of the find command.

And finally  the command uniq merge the duplicate lines to the unique.And the -c option shows the repeated counts.So the count number represents the file counts in the directory at the same time.

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The first image shows the output of the command:
strings /usr/bin/yes

and the second image is the output of the command:
cat /usr/bin/yes

So have you known the difference between two commands?
Yes,the strings will prints the character sequences in the binary file,but cat can't.Let's check the man's explanation.

Strings
For  each  file  given,  GNU  strings  prints  the  printable character sequences that are at least 4 characters long (or the number given with  the  options  below)  and are followed by an unprintable character. 
     

    So strings is a mainly useful command for  determining  the  contents  of  non-text  files.

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What's the Issue?

Since most Ubuntu documentation asks you to use sudo even with graphical applications, I often get asked by Ubuntu users why I recommend gksudo or kdesu for graphical applications instead of sudo.

For example, a lot of guides (including the first book ever published about Ubuntu) will ask you to type this sort of command:

sudo gedit /etc/apt/sources.list
I will always recommend, however, that people use instead this sort of command:

gksudo gedit /etc/apt/sources.list
And reserve sudo for command-line applications, like so:

sudo nano /etc/apt/sources.list
Why is it an issue?

Well, to be perfectly honest, most of the time it isn't. For a lot of applications, you can run them the improper way—using sudo for graphical applications and see no adverse side effects.

1. There are other times, though, when side effects can be as mild as Firefox extensions not sticking or as extreme as as not being able to log in any more because the permissions on your .ICEauthority changed. You can read a full discussion on the issue here.
These errors occur because sometimes when sudo launches an application, it launches with root privileges but uses the user's configuration file.

For example, if you launch Firefox with the command
gksudo firefox
, it uses root's Firefox configuration file.


But if you launch Firefox with the command
sudo firefox
, it runs with root privileges but uses the user's configuration file (in this case, you can see the homepage and theme are different).

2. Running graphical applications with sudo also has the downside of always having to be run from the terminal. If you don't use the proper command—gksudo or kdesu, you will not be able to use the command as an icon launcher or keyboard shortcut because there will be no graphical dialogue box to enter your sudo password in.

3. There are also some graphical applications that simply will not run with the sudo command. Kate, for example, can be run as
kdesu kate
but cannot be run as
sudo kate

Why not make exceptions?

Bottom line: most of the time when you use sudo for graphical applications, it's fine. Some of the time, though, it is not fine, and is, in fact, extremely bad.
If you made exceptions, you would have to give people a list of all the graphical applications that are okay to run as sudo and a list of all the graphical applications that must be run as gksudo or kdesu.
Why make a list that needs to be compiled and updated, that most people won't refer to, and that is completely unnecessary? Just be consistent in suggesting good practice: gksudo and kdesu for graphical applications. sudo for command-line applications.

But gksudo sometimes gives me an error... even though it appears to work...

You may notice that even though gksudo is the proper way to launch graphical applications, if you launch a gksudo application it will sometimes give you what appears to be an error. This, for example:

(gedit:####): GnomeUI-WARNING **: While connecting to session manager:
Authentication Rejected, reason : None of the authentication protocols specified are supported and host-based authentication failed.
That is not a real error, and there's already been a bug report filed on the message appearing. The developers have seen the bug and labeled it a low priority. In the meantime, just ignore the message and keep encouraging people to not use sudo for graphical applications so they won't potentially mess up their ~/.ICEauthority and other user configuration files.

from:http://www.psychocats.net/ubuntu/graphicalsudo

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ps

run without parameters will only show you  the process associated with the current terminal:

$ ps

          PID TTY            TIME CMD

      18614 pts / 3 00:00:00 bash

      20173 pts / 3 00:00:00 ps

Like many UNIX ® tools, ps also has a lot of options, the most commonly used are:

       a: shows all tty, including other users;
   
       x: print non-controled terminal or the tty which not controled by current terminal;

       u: display user-oriented format,shows the user and the start-up time of the process.

need other relevant options, please refer to ps (1) manual page.

the ps command is commonly used as follows:

$ ps ax | less

This command will print the list of all processes that is currently running , so you can find out where or what the processes that have problems, and then terminate them.

pstree

pstree command is used to display the process tree. The advantage is that you can immediately find out the parent process of a process: when you want to terminate the entire series  of the process and there are many subordinate branches of the process, what do you need to do is to terminate the process at the top level. You may need to use the -p option to display each process's PID, as well as the -u option to display the user of the process. In general, the tree struct of the process is very long, you need to run pstree just like this:

$ pstree-up | less

This will allow you to overview the entire tree structure of processes .

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