virsh (un)define

kvm virsh tool has nice features to define and undefine particular virtual machine.If we have .xml kvm machine file then using
#virsh define kvmmachine.xml
will define it and machine will be ready for use.If you,as I do very often,need to deploy same virtual machine name ( eg: new / full clone of cluster node ) then cloning machine will not allow you to use same name as it is internally remembered by kvm.Reboot of host will fix this,but that is not solution ;), for such cases,
#virsh undefine kvmmachine
will undefine machine ( remove its name from kvm namespace ) and you can clone it again.Notice that when # virsh undefine kvmmachine is used we use virtual machine name as (was) visible in #virsh list output




If you have Raspberry PI and decide to use it media center,you will probably look for Raspberry PI ready player.

omxplayer is tool for you

#aptitude install omxplayer xterm

to start using it, right click on desired video->open with->and enter below for custom command

xterm -fullscreen -fg black -bg black -e omxplayer -o hdmi -r %f

to get it running in full screen mode.

#linux, #omxplayer, #raspberry-pi


With Red Hat based distributions ( Centos, Sciencific Linux, Oracle Linux, Fedora 😉 ) adding new iptalbes rules is as easy as editing /etc/sysconfig/iptables or running iptables-save after adding new rules – iptables-save will automatically edit /etc/sysconfig/iptables and add new rules there.

For Debian,there is also an easy way to ensure iptables rules to start on boot – use iptables-persistent package which is an boot-time loader for iptables rules.

#aptitude install iptables-peristent

After installation we can find files which are part of iptables-persistent

#dpkg -S iptables-persistent
iptables-persistent: /usr/share/doc/iptables-persistent/README
iptables-persistent: /usr/share/doc/iptables-persistent
iptables-persistent: /etc/init.d/iptables-persistent
iptables-persistent: /usr/share/doc/iptables-persistent/changelog.gz
iptables-persistent: /usr/share/doc/iptables-persistent/copyright

for us is interesting /etc/init.d/iptables-persistent script,from where we see

        log_action_begin_msg "Loading iptables rules"

        #load IPv4 rules
        if [ ! -f /etc/iptables/rules.v4 ]; then
                log_action_cont_msg " skipping IPv4 (no rules to load)"
                log_action_cont_msg " IPv4"
                iptables-restore  /dev/null
                if [ $? -ne 0 ]; then

        #load IPv6 rules        
        if [ ! -f /etc/iptables/rules.v6 ]; then
                log_action_cont_msg " skipping IPv6 (no rules to load)"
                log_action_cont_msg " IPv6"
                ip6tables-restore  /dev/null
                if [ $? -ne 0 ]; then

        log_action_end_msg $rc

if you have ipv4 rules,then they will be saved in /etc/iptables/rules.v4, in case of ipv6 rules, they will go to /etc/iptables/rules.v6

Rough steps may be, create iptables script file,test….test it,execute it, save rules with iptables-save > /etc/iptables/rules.v4,and that is.iptables-save will send them to /etc/iptables/rules.v4 ( for ipv6, you will need to use ip6tables commands in order to update /etc/iptables/rules.v6 file ) – next time machine boots, iptables-persistent will read and apply them from there.


unalligned pointer debian bug …

Fedora 17 host + ( kvm ) debian 6 guest … ends as showed below.Seems nice homework :). Anybody out there has already solution? Thanks


Happy b-day Debian :) … long live

The Debian Administration Handbook released

The Debian Administration Handbook is online available.
More details — Debian Handbook official web page.

Debian is great linux distribution,and releasing The Debian Administration Handbook will help to make it even better.

Book is possible to get for free ( pdf, mobi, epub formats ),but if your financial situation allows,I fully recommend to buy hard copy and help Debian project

Thanks to Raphaël Hertzog for work on it

Enjoy The Debian Administration Handbook 🙂


Fight against ISP rules

When I am on road I am forced to use internet connection at homes of my friends / family,but that is very often an interesting experience.

The thing I do not understand when it comes to ISP business is rule to lock MAC address of 1 ( one ) machine and do not allow to connect another machine to network ( yes,they allow that but you will need to call them to change MAC address at their side )

To all WW ISPs: What is issue to allow to connect another laptop to internet and why is so important to lock computer’s MAC?

I want to use my laptop to browse internet,and it is funny to see that only one machine is “internet-able”.

Changing MAC address is super easy task,put below in some script eg,

ifconfig eth0 down
ifconfig eth0 hw ether 00:11:D8:D3:26:FE
ifconfig eth0 up

copy script to /etc/init.d/ and execute

# update-rc.d -n defaults

Above MAC address is one in my case,replace it with MAC address of machine which is “internet-able” in your case 😉

Above applies for Debian and problem is “solved”.Next time you boot machine with connected cable it will be automatically connected,ISP will think that there is not change,they only care about MAC – at least ones I had to deal with.Above script can be executed manually too.

But still I do not see purpose of this ISP practice,ISP guys changing MAC address never was an “rocket science”