md5sum

md5sum is a wide-used tool for checking the integrity of files after data transfers. Especially, when you download some big files (such as image of system), you may want to ensure that the huge files have been fully correctly download to your local disk. Usually, data privider will offer a md file to let user check the integrity. See the example in http://downloads.openwrt.org/backfire/10.03/rb532/. After download all the data files,  you also need to download the md5sums file into the same directory and run

>md5sum -c md5sum

About how to create a md file is shown below:
>md5sum file > file.md5 (single file)
>find directory -type f -print0 | xargs -0 md5sum >> file.md5 (all file in a directory)

Reference:

• md5sum wiki

nfs-kernel-server vs. nfs-user-server

Max tried to install nfs-server on his Debian machine.
>sudo apt-get install nfs-kernel-server
Everything looks fine, except of this warning message:

Not starting NFS kernel daemon: no support in current kernel. (warning)

It seems that the current kernel doesn't support nfs kernel daemon. After googling for sometime, I found that rebuild the kernel is the solution for the problem (http://computingplugs.com/index.php/NFS_server). It is funny that my self-built kernel 2.6.34 has no the option

[*] Root file system on NFS

in 'make menuconfig'.

The other solution is to install nfs-user-server, which runs in the user-mode, not in kernel-model.

>sudo apt-get install nfs-user-server
>/etc/init.d/nfs-user-server restart

Reference:

• nfs-user-server

Difference between Virtualbox and Virtualbox-ose

The full VirtualBox package is available in binary (executable) form free of charge from the Downloads page. This version is free for personal use and evaluation under the terms of the VirtualBox Personal Use and Evaluation License.

The VirtualBox Open Source Edition (OSE) is the one that has been released under the GPL and comes with complete source code. It is functionally equivalent to the full VirtualBox package, except for a few features that primarily target enterprise customers. This gives us a chance to generate revenue to fund further development of VirtualBox.

Reference:

• Open Source VirtualBox and other editions
• Build instructions 

Description of /apt/etc/sources.list

#####################
deb http://ftp.de.debian.org/debian/ lenny main non-free contrib
deb-src http://ftp.de.debian.org/debian/ lenny main non-free contrib
#####################

deb/deb-src, indicates the type of archive: whether it contains binary packages (deb) or source packages (deb-src)
http://ftp.de.debian.org/debian/: repository of packages, it can be ftp, http, file and so on.
lenny: distribution, e.g. stable, testing sid...
main non-free contri: different licence sections in the package repository.

• main: the official Debian distribution, full free use and redistribution.
• contri: Packages in this area are freely licensed by the copyright holder but depend on other software that is not free.
• non-free:  Packages in this area have some onerous license condition restricting use or redistribution of the software.

A Short Summary of Debian Package Management

# apt-get update (update local database using newest sources.list)
# apt-cache search string (search all packages contain the string)
# apt-get install package (install package)
# apt-get remove package (remove package)
# apt-get --purge remove package (remove package and config files)
# apt-cache show abcde (show info of package, e.g. dependency..)
# apt-get dist-upgrade (upgrade the installed package to latest version)

Reference

• Debian package management, distributions and the /etc/apt/sources.list file

Restart bash after change .bashrc

>source ~/.bashrc

Full Screen Mode of Virtualbox

Left-Ctrl + F is the shortcut to switch between full screen and normal screen modes for virtualbox.