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--- soc:2009:pravin:journal:ubuntubko [2009/06/25 13:36]
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+++ soc:2009:pravin:journal:ubuntubko [2009/07/27 05:26] (current)
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 ===== Locating from where does the nfsboot is getting called =====
-  - //do_nfsmount// function is getting called from ///scripts/casper +188//
+==== Mistory of do_nfsmount ====
-  - //do_nfsmount// is defined at two places, why?
+//do_nfsmount// is defined at two places, why?\\
-  - My guess is that file //script/nfs// is not used, it is just present there.
+  - ///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''
+===== Solution =====
+The temporary hack implemented is **Delete these two files** before doing ''run-init''.  This hack works fine in this case, only problem is that the ''/etc/resolver.conf''
+entry remains empty so dns resolving does not work.  Need to fix this soon.

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