✎ soc:2009:pravin:journal:ubuntubko

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== Booting Ubuntu with BKO ======

===== Locating from where does the nfsboot is getting called =====
==== Mistory of do_nfsmount ====
//do_nfsmount// is defined at two places, why?\\
  - ///scripts/casper +198// 
  - ///scripts/nfs +8//
My guess is that file ///scripts/nfs// is not used, it is just present there from older versions and has not been removed.\\

//do_nfsmount// function is getting called from ///scripts/casper +188// which is from inside of <code>do_netmount()</code> and depend on variable <code>${NETBOOT}</code>

The //do_netmount()// is getting called from //mountroot()// which is inside ///scripts/casper +581// and the call depends on variable presense of variable //${NETBOOT}// which is the boot parameter value of parameter //netboot//

===== qemu + ubuntu 9.04 Desktop i386 booting problem =====
ubuntu-9.04-desktop-i386.iso is refusing to boot over qemu.
I am using command line
<code>
qemu -cdrom /var/www/ubuntu-9.04-desktop-i386.iso -net nic -net user
</code>
It gives error gives error :
<code>
[  3.284007]  ..MP-BIOS bug: 8254 timer not connected to IO-APIC
</code>
and freezes.\\
I am using following version of qemu 
<code>
$ qemu
QEMU PC emulator version 0.10.0, Copyright (c) 2003-2008 Fabrice Bellard
</code>
The BIOS number was found 
and BIOS version used by qemu is as follows
<code>
QEMU BIOS - build: 08/15/08
$Revision: 1.209 $date: 2008/06/02 20:08:10$
</code>

I had to update my qemu to version 0.10.5 then it started working
<code>
$ qemu
QEMU PC emulator version 0.10.5, Copyright (c) 2003-2008 Fabrice Bellard
</code>
===== SQUASHFS error =====

I am getting following errors in the process of booting. My guess is, most of these
errors are related to failure of httpfs in providing requested logical block, but I need to confirm this.
<code>
Buffer I/O error on device loop0, logical block 272374
SQUASHFS error: sb_bread is failed reading block 0x845d5
SQUASHFS error: unable to read fragment cache block [211696cb]
SQUASHFS error: unable to read page, block 211696cb, size c115
</code>
I have seen this error before, but if I retry the booting then it works.
But now, I have failed two consecutive time on local webserver, which is quite alarming.

====== Ubuntu revisited (in way of debian) ======

I was preparing to write an email to ubuntu mailing list, here is what I assembled for that email
<code>
I have tried booting Knoppix and debian over HTTP, and they work fine.
But I have problem in booting Ubuntu (ubuntu-9.04-desktop-i386.iso) over HTTP.

The procedure followed to boot linux over HTTPFS by me is as follows.
I get hold of ISO of live CD, and get the kernel, initramfs and 
filesystem.squashfs from it.
I host ISO of live CD and "filesystem.squashfs" on webserver.
I modify initramfs to include httpfs and related tools and modules.
I modify "/init" ( "/scripts/casper" in case of ubuntu ) to use httpfs 
for mounting. 
I pass boot parameter "httpfs=http://ip-of-webserver/filesystem.squashfs" 
or "httpfs=http://ip-of-webserver/ubuntu-9.04-desktop-i386.iso"

I have attempted booting with both livecd.iso and filesystem.squashfs.
In both cases, I get different errors.

I know that filesystem is getting mounted with HTTPFS. 
I have verified it from the rescue shell.
I get this rescue shell by executing wrong command in initramfs. 


When I mount "ubuntu-9.04-desktop-i386.iso" I get following error
{{{
Buffer I/O error on device loop0, logical block 272374
SQUASHFS error: sb_bread is failed reading block 0x845d5
SQUASHFS error: unable to read fragment cache block [211696cb]
SQUASHFS error: unable to read page, block 211696cb, size c115
}}}


Then I tried to use debian way of mounting "filesystem.squashfs" for booting.
I get error
{{{
Begin: Running /scripts/init-bottom ...
Done.
run-init: nuking initramfs contents: Directory not empty
Kernel panic - not syncing: Attempted to kill init!
Dumping ftrace buffer:
	(ftrace buffer empty)
}}}


My guess is that, this error is triggered because when "/bin/run-init" 
tries to remove initramfs and fails to remove some file. Most probably it 
can be /dev/loop0 as it is in use by loopback mount command.

I checked debian code, the use of loopback is avoided there.
So, I am doing the same for ubuntu now. 
I wont use loopback and see if it works.



I was wondering what I am doing wrong as the same method works fine with debian.
And when I try to mount ISO itself, I get kernel panic

</code>

Got some information about this error on [[http://wiki.debian.org/initramfs/More|debian wiki]]
which says that
<code>
When switching another root device, initrd would pivot_root and then umount the ramdisk. But initramfs is rootfs: 
you shouldn't pivot_root rootfs and can't unmount it. Just delete everything out of it (except the new block device node, if any),
 overmount /, and exec the new init. (The klibc package contains a helper program in utils/run_init.c to do this for you, 
and other packages have adopted this as switch_root.) 
</code>

Now, I don't know for sure, which files are not getting deleated and hence causing problem.

==== A question ====
what is the differnece between debian script and ubuntu script that filesystem.squashfs is not working with ubuntu, but it works with debian?

   - comparing ''d/scripts/live'' with ''u/scripts/casper'' --- too different, diff went crazy with this command.  They are as good as seperate program who do similar work.
   - comparing ''d/bin/run-init'' with ''u/bin/run-init'', --- they are same.
   - comparing ''d/init'' with ''u/init'' -- not much of difference

This approach is not working for me, I will try another approach.

==== analyzing run_init.c ====
My guess is that, run_init.c is the one who is dying, and it seems he does allow you to specify the files which should not be deleted.
I want to see how to tell that to run_init.c
  - Another thing that I want to try out is, what if I dont delete the contents of initramfs? I will remove that check from run_init.c will system still boot?
    - My guess is that, ''overmount /'' may fail.
  - Now, I need to locate the source code of run_init.c

===== Ubuntu over iscsi =====
  - Following the line of [[BKODebianISCSI|Debian over iscsi]], attempted the Ubuntu over iscsi, but it did not worked.


===== Problem found =====
  - From the progress in fedora, it seems that problem is because network is restarting itself, which kills the the network and mounted HTTPFS.  Culprits are 
    - ''/etc/init.d/network''
    - ''/etc/init.d/NetworkManager''
Trace: • week5 • uhci_port_reset_issue • probsbkoromomatic • fedora11bko • week12 • bkostaticip • week12 • week11 • week7 • week6 • week3 • week4 • week2 • week11 • week4 • audit-the-shifts • week2 • week4 • journal • usb_todo