Compiling Xen from source using dpkg

Compiling and installing software from source is used by developers a lot. So using ./configure , make, make install is something we all are well aware of but this is a very messy way to do so because when you uninstall the program it may leave some dependency files in the system or might not work properly when again installed.

I observed this case a lot of times when I use make install. Even sometimes a tried removing extra programs/dependencies manually.
So now I will write about a clean and very good way of installing Xen by source.

Download Xen sourcecode from git.

And run these commands:
#cd xen
#./configure –prefix=/usr
#make
#make debball
#dpkg -i dist/xen-upstream-XXXX

And whenever you want to uninstall it just use.

#dpkg -r xen-upstream
#apt-get purge xen-upstream

And yes you don’t have to worry about any of the dependencies as dpkg will take care of it. 🙂

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Creating guests using xl in Xen

This post is about creating guests after Xen is installed. There are several ways to do that. But after using them this is the one that I preferred i.e. creating guest manually using xl. If you want a fancy GUI then one can use virt-manager but that going to create a mess if you installed Xen from source. So if you are installing Xen using source code then this is worth a try. 🙂 My mentors suggested and helped me to try it and I can say its pretty amazing and simple. So the following steps create a guest ubuntu-guest. The following steps create an disk image for the guest ubuntu-guest4.

sudo mkdir -p /var/lib/xen/images
sudo dd if=/dev/zero of=/var/lib/xen/images/ubuntu-guest4.img bs=1M seek=15096 count=0
sudo mkfs.ext4 -F /var/lib/xen/images/ubuntu-guest4.img (optional if using iso for installation)

Then create file /etc/xen/ubuntu-hvm4.cfg for configuration details of guest. Mine looks like the below.

In line stating the disk home/uma/Desktop/OS/ubuntu-12.04-desktop-amd64.iso should be replaced by the address of your iso file.

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xl create /etc/xen/ubuntu-hvm4.cfg

(This will open your guest console :D)

After installing OS you can shutdown the guest and change the disk line in /etc/xen/ubuntu-hvm4.cfg to

disk = [‘phy:/var/lib/xen/images/ubuntu-guest4.img,hda,w’]

And start using your guest. 😀

My First Experience with GRUB

Hi Friends. So, here I am again there with my experience and I think my GRUB experience (till now) would be an amazing topic

So let us start from the start 🙂

What is GRUB ?

GRUB is a boot loader designed to boot a wide range of operating systems from a wide range of file systems. (copied :-p)

GRUB creates and manages the screen containing list of OS available in the system that we see while booting process. (in simple language)

Why I felt the need to change GRUB boot loader?

1. To make the boot menu visible

When Xen hypervisor is installed in Ubuntu 14.04 or higher versions it automatically changes the GRUB to boot XEN and hides the OS list menu on boot. So, if you want the menu to appear on boot then follow the steps :

Open /etc/default/grub and change GRUB_HIDDEN_TIMEOUT

GRUB_HIDDEN_TIMEOUT=-1

And then update your grub by running the following command

update-grub2

and on next boot you will see the boot menu 🙂

2. To pass boot parameters to Xen

I have to change the scheduler in Xen to credit2 scheduler and for that I have to pass the parameters to Xen kernel.

Open /etc/default/grub and append the following line at the end

GRUB_CMDLINE_XEN=”sched=credit2″

And update your grub

update-grub2

So to pass parameters to Xen Kernel you just have to insert parameters between ” ”

Example

GRUB_CMDLINE_XEN=”sched=credit2  cpuinfo=1″

grub

But this is not an end I will keep updating about GRUB. 🙂