====== Debian Tips ======

===== Safely change a kernel boot option =====

When changing specific kernel boot option in grub, you might want to keep this even after a kernel upgrade (which rebuild the grub configuration). 
So you'll have to go to ''/boot/grub/menu.lst'' and find the ''kopt'' comment in this file :
<code># kopt=root=/dev/sda1 ro</code>

This line specific what kernel options should be set by Debian when updating grub configuration.

===== Change default text editor =====
Run  ''update-alternatives'' :

<code># update-alternatives --config editors</code>


===== Revert Debian upgrade =====
When upgrading, you might like to revert back to a specified moment in time. Reverting upgrade seems stupid, but ISO Certification ask to have a defined process for that. So here we are :

Modify ''/etc/apt/sources.list'' and set (for 19 November 2007, here):
<code>deb http://snapshot.debian.net/archive/2007/11/19/debian stable main non-free contrib
deb http://snapshot.debian.net/archive/2007/11/19/debian-security stable/updates main non-free contrib</code>

Then in ''/etc/apt/preferences'' :
<code>Package: *
Pin: release a=stable
Pin-Priority: 1001</code>

And finally you just need to ''apt-get update && apt-get dist-upgrade'' !

See [[http://lists.debian.org/debian-user-french/2007/12/msg00529.html]]

===== Install Xvfb =====

[[wp>Xvfb|Xvfb]] is virtual X11 Server that works only in memory.

<code>time:/# aptitude install xvfb xdm</code>
Then edit ''/etc/X11/xdm/Xservers'' and change the line :

<code>:0 local /usr/bin/X vt7 -dpi 100 -nolisten tcp</code>

to

<code>:0 local /usr/bin/Xvfb -dpi 100 -screen 1024x768x16</code>

Finally start XDM :
<code>/etc/init.d/xdm start</code>

This will create a virtual X server at the size defined by ''screen'' option. Useful when forwarding via SSH !



===== Install Flash Player =====

To install Flash Player :

Go to [[http://http.us.debian.org/debian/pool/contrib/f/flashplugin-nonfree/]], select the ''.deb'' corresponding to what you want and download :

<code>time:/# wget http://http.us.debian.org/debian/pool/contrib/f/flashplugin-nonfree/flashplugin-nonfree_9.0.115.0.1_i386.deb</code>

Then with ''dpkg'', install :

<code>time:/# dpkg -i flashplugin-nonfree_9.0.115.0.1_i386.deb</code>


===== Stop kernel message on console =====

<code>time:/# echo "0" > /proc/sys/kernel/printk</code>


===== Convert filename encoding =====

If you have moved files from a system using ISO-8859-1 encoding to UTF-8, you might have filename looking like ''Norme_int�gration.pdf''.
There's a good tool : ''convmv''.

<code>#aptitude install convmv</code>

Then just read the manual : [[http://www.j3e.de/linux/convmv/man/]]


===== Hibernate from Gnome menu reboot instead of shutdown =====
<note warning>This was done on Debian **[[http://www.us.debian.org/releases/testing/|Lenny]]**</note>

On a //HP DC7800p//, I had problem with hibernation from Gnome menu (''System'' -> ''Shut Down ...'' -> ''Hibernate''). 
Indeed my computer rebooted instead of powering off, to correct this behavior I just created the file ''/etc/pm/config.d/shutdown'' with ''HIBERNATE_MODE=shutdown'' !

More info with ''man pm-hibernate''.

===== Dynamic MMap ran out of room =====

I had problem with ''aptitude''. When I did ''aptitude update'', I got something like "Dynamic MMap ran out of room". So here is the solution I used to correct : [[http://vdachev.net/blog/2006/11/13/apt-get-e-dynamic-mmap-ran-out-of-room/]].

The value given may be not enough, I needed to enlarge this value to make it works.