Xvnc versus X11vnc

What is the difference between Xvnc and X11vnc?

Xvnc: Is an X and VNC server at the same time. It is mainly used to run the X server on a virtual display, (in the absence of a physical one) and connect remotely to it with a VNC client/viewer.

X11vnc: Is a vncserver that “publishes” an existing physical X display over VNC, allowing remote clients to connect with it using a VNC viewer. That is, they can see the actual running desktop windows, as if they were in front of the server.

Bash ‘help’

Some commands you type in the shell are actually not binaries but shell (bash for example) buitins. For example, “alias” is such an shell builtin.

~# type alias

alias is a shell builtin

~# man alias

No manual entry for alias

In order to obtain more information about the “alias” builtin, you should type “man bash” and search what you are looking for in the hundreds of pages long man.

However, there is a quicker way! “help” helps you:

~# help alias

alias: alias [-p] [name[=value] … ]

    Define or display aliases.

    Without arguments, `alias’ prints the list of aliases in the reusable

    form `alias NAME=VALUE’ on standard output.

    Otherwise, an alias is defined for each NAME whose VALUE is given.

    A trailing space in VALUE causes the next word to be checked for

    alias substitution when the alias is expanded.    

    Options:

      -p Print all defined aliases in a reusable format

    Exit Status:

    alias returns true unless a NAME is supplied for which no alias has been

    defined.

 

Yum provides…

Yum, the preferred RPM package manager makes our lives a bunch easier when you need to install new packages.
Below an example of a nice feature that yum “provides”.

[pieter@laptop ~] nslookup www.google.com

bash: nslookup: command not found

[pieter@laptop ~] yum search nslookup
Loaded plugins: fastestmirror, langpacks, presto, refresh-packagekit
Loading mirror speeds from cached hostfile
Warning: No matches found for: nslookup
No Matches found

Doooooh!! Now what?

In Yum’s man page (man yum) we find our rescue:

provides or whatprovides

Is used to find out which package provides some feature or file. Just use a specific name or a file-glob-syntax wildcards to list the pack‐
ages available or installed that provide that feature or file.

[pieter@laptop ~] yum provides */nslookup

Loaded plugins: fastestmirror, langpacks, presto, refresh-packagekit
Loading mirror speeds from cached hostfile

32:bind-utils-9.8.1-2.fc16.x86_64 : Utilities for querying DNS name servers
Repo : fedora
Matched from:
Filename : /usr/bin/nslookup

32:bind-utils-9.8.2-0.2.rc1.fc16.x86_64 : Utilities for querying DNS name servers
Repo : updates
Matched from:
Filename : /usr/bin/nslookup

As we can see from Yum’s output, the package we need to install in order to have nslookup is “bind-utils”

[pieter@laptop ~] yum install -y bind-utils

[..output stripped…]

[pieter@laptop ~] nslookup www.google.com
Server: ******
Address: *****#53

Non-authoritative answer:
www.google.com canonical name = www.l.google.com.
Name: www.l.google.com
Address: 74.125.230.242
Name: www.l.google.com
Address: 74.125.230.243
Name: www.l.google.com
Address: 74.125.230.244
Name: www.l.google.com
Address: 74.125.230.240
Name: www.l.google.com
Address: 74.125.230.241

Huray!