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Mounting partitions with chroot in rescue mode

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You need to "transplant" /proc pseudo filesystem

mount --bind /proc /chrooted/proc

then

chroot /chrooted

--bind is for mount an already mounted filesystem to another mount point. i got it from here. i can't find
it in my man page either, but i know i've read about it somewhere. i just can't find it.

Recover Root Password - openSUSE

Set Root Password

If you've lost your root password, you might be able to recover it using the steps below. However, some systems are protected with boot loader passwords that will not let you do that without THAT password. If the boot loader is password protected, you need to boot from other media Like the OpenSUSE CD/DVD/mini-boot. OpenSUSE install CD is probably the best one to use.

CD/DVD Recovery Mode

If using CD/DVD boot media, You need to choose Rescue System. You enter root and then mount the disk manually. For example, a Compaq raid controller will probably be /dev/ida/c0d0 or an IDE drive will be /dev/hda1. Find the partitions by using fdisk /dev/ida/c0d0 or fdisk /dev/hda (just "p" and quit) and then mount what you need.

mount -o remount,rw /dev/sda2 /mnt
# cd /mnt
# chroot /mnt
# passwd

For 10.3, you need somemore steps:

Start the rescue system. Find the disk root partition, then, assuming its hdxy (or probably sdxy):

mount /dev/hdxy /mnt
mount -o bind /proc /mnt/proc
mount -o bind /sys /mnt/sys
mount -o bind /dev /mnt/dev
chroot /mnt

you are root in the installed sytem, with all at hand: passwd, but also YaST...

"bind" allow using two mount points for system virtual folders.

If all fails, consider that you can pull this drive (or install another drive in this machine) and mount it from another running Linux. Then recover the root password as explained above.

Single User Mode

The first thing to try is to boot to single user mode. This MIGHT not work for you, because your system might be configured to still ask for a root password to get to single user mode. If that's the case, we'll use another trick that replaces init with /bin/bash.

First, try single user. If you don't see either a LILO or GRUB boot screen, try hitting CTRL-X to get one. If it's LILO, just type "linux single" and that should do it (assuming that "linux" is the lilo label). If GRUB, hit 'e", then select the "kernel" line, hit "e" again, and add " single" (or just " 1") to the end of the line. Press ENTER, and then "b" to boot. (Newer version of grub uses "a" to append to the boot line)

You should get a fairly normal looking boot sequence except that it terminates a little early at a bash prompt. If you get a "Give root password for system maintenance", this isn't going to work, so see the "init or /bin/bash" version below.

If you do get the prompt, the / filesystem may not be mounted rw (although "mount" may say it is). Do

mount -o remount,rw /

If that doesn't work (it might not), just type "mount" to find out where "/" is mounted. Let's say it is on /dev/sda2. You'd then type:

mount -o remount,rw /dev/sda2

If you can do this, just type "passwd" once you are in and change it to whatever you like. Or just edit /etc/shadow to remove the password field: move to just beyond the first ":" and remove everything up to the next ":". With vi, that would be "/:" to move to the first ":", space bar once, then "d/:" and ENTER. You'll get a warning about changing a read-only file; that's normal. Before you do this, /etc/shadow might look like:

root:$1$8NFmV6tr$rT.INHxDBWn1VvU5gjGzi/:12209:0:99999:7:-1:-1:1074970543
bin:*:12187:0:99999:7:::
daemon:*:12187:0:99999:7:::
adm:*:12187:0:99999:7:::

and after, the first few lines should be:

root::12209:0:99999:7:-1:-1:1074970543
bin:*:12187:0:99999:7:::
daemon:*:12187:0:99999:7:::
adm:*:12187:0:99999:7:::

You'll need to force the write: with vi, ":wq!". (If that still doesn't work, you needed to do the -o remount,rw, above).

INIT or /bin/bash Mode

Another trick is to add "init=/bin/bash" (LILO "linux init=/bin/bash" or add it to the Grub "kernel" line). This will dump you to a bash prompt much earlier than single user mode, and a lot less has been initialised, mounted, etc. You'll definitely need the "-o remount,rw" here. Also note that other filesystems aren't mounted at all, so you may need to mount them manually if you need them. Look in /etc/fstab for the device names.

Keep this in mind if you have a Linux machine in a publically accessible place : without more protection, it's not usually hard to recover a lost root password, which means it's just as easy for someone to CHANGE it, or access root without your knowledge.

Another way to do this is to remove the password from /etc/shadow. Just in case you screw up, I'd copy it somewhere safe first. You want to end up with the root line looking something like this:

Original line:

root:$1$EYBTVZHP$QtjkCG768giXzPvW4HqB5/:12832:0:99999:7:::

After editing:

root::12832:0:99999:7:::

If you are having trouble with editing (you really do have to learn vi one of these days), you could just (after making a copy, of course) just

 echo  "root::12832:0:::::" > /mnt/etc/shadow 

or, if you were in single user mode

 echo  "root::12832:0:::::" > /etc/shadow 

and then fix things up when rebooted.

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Blang! » SUSE Broken Don’t fear the chroot !

Posted by johnlange on September 22, 2009 06:45 pm under SUSE, Tech Tip

SUSE hasn’t let me down very often but recently I had a bad experience while applying some updates to an OpenSUSE laptop. There were quite a few updates so I undocked the laptop so I could relax while they downloaded.

For reasons that I have not yet resolved, the wirless networking became unstable and as a result, the updates had to be aborted.

Unfortunately, a new kernel was part of the updates and when the laptop rebooted it was in a bad state. X windows wouldn’t start and critically, there were no network drivers for the new kernel. To make matters worse, OpenSUSE does not keep the old kernels in /boot (why is that?) so there was nothing to fall back on.

With nothing left to do, it was time to try rescue mode and in a few short steps I had the system fully working again. Here is what I did:

Step 1: boot to rescue mode (duh).

Step 2: mount your hard disk partitions under /mnt in the same layout they would be normally. For example:

# mount /dev/sda2 /mnt
# mount /dev/sda1 /mnt/boot

… etc.

Step 3: Next we need to make sure we have acess to all the important system resources.

# mount --bind /proc /mnt/proc
# mount --bind /sys /mnt/sys
# mount --bind /dev /mnt/dev

Step 4: We’re ready to chroot into our new environment.

# chroot /mnt

Step 5: We are now running on our system just as if we had booted to it and we can perform repairs. In my case all I needed to do was complete the updates:

# zypper up

I rebooted and everything was back to normal.

USING A RESCUE CD to restore GRUB to MBR
I am using sysresccd aka system rescue cd from www.sysresccd.org

INTRODUCTION
Rescue cds always tend to mount any partitions they discover as read only but we need them as read writeable.
eg knoppix makes my partitions available on the desktop for reading only.

Know where your /boot partition is....mine is /dev/hda1 change yours to suit.

STEP by STEP
Change bios to boot cdrom b4 hard or floppy drives

With cd in drive, boot the computer and assuming English keep pressing enter at the prompts, until you get a console or terminal prompt. If you have a non-qwerty keyboard the second prompt allows you to change the keyboard.

type su press enter

type mkdir /mnt/newroot press enter

mount your real /boot partition for me its
type mount -t reiserfs /dev/hda1 /mnt/newroot press enter

type chroot /mnt/newroot /bin/bash press enter

type grub press enter
# prompt will change to grub then then the cursor


type root (hd0,0) press enter (change if /boot partition different)

type setup (hd0) press enter

reboot and remove cd.

EXPLAIN

su = setuser to root no password is requied for knoppix or sysrescd

mkdir = make directory to anything you like but I suggest if you are reading this don't change it.
Its only a directory in your virtual = ram drive = ram disk so on reboot IT is not there.

mount means make your /boot partition readable and writeable. Yours may not be reiserfs so change reiserfs to whatever you are using.
/bin/bash is what I use, as do most newbies.

chroot means ignore all rescue cd file system, trick it into thinking your old system is back already.

grub = bootloader

root see my tutorial if you don't know how to use root

setup means let grub do its business

http://www.ibiblio.org/pub/Linux/doc...istro-Dev.html

problem trying to chroot from liveCD to fix system - openSUSE Forums

My 11.3 install boots to a white screen. I have tried booting to runlevel 3 but I get the same screen there also. It is mostly white with some garbage at the top. So I am trying to chroot into it to update the system and I am getting the following error. What am I doing wrong?
 

Code:

linux@linux:~> su -
linux:~ # mkdir /mnt/suse5
linux:~ # mount /dev/sda5 /mnt/suse5
linux:~ # mount --bind /proc /mnt/suse5/proc
linux:~ # mount --bind /dev /mnt/suse5/dev
linux:~ # mount --bind /dev/pts /mnt/suse5/dev/pts
linux:~ # mount --bind /sys /mnt/suse5/sys
linux:~ # mount --bind /etc/resolv.conf /mnt/suse5/etc/resolv.conf
linux:~ # chroot /mnt/suse5 /bin/bash
linux:/ # zypper up
zypper: error while loading shared libraries: librpm.so.0: cannot open shared object file: No such file or directory
linux:/ #

 

search

grub-install does not see block device while being in chroot user environment

Running grub-install block device while being chrooted after booting into the rescue mode causes the error:

block device: Not found or not a block device.


While in chroot mode issuing lsscsi reports:

error: Unable to open /proc/mounts for reading Unable to locate sysfsroot. If kernel>= 2.6.0 Try something like 'mount -t sysfs none /sys'.
 

Resolution

Before changing environment to root the following commands needs to be issued:

mount --bind /proc /CurrentMountPointofRootPartition/proc
mount --bind /dev /CurrentMountPointofRootPartition/dev
mount --bind /sys /CurrentMountPointofRootPartition/sys

After that the command chroot /CurrentMountPointofRootPartition can be issued and the virtual proc, sys and dev filesystems will be available from within the chroot environment so that commands like grub-install can function.

 

Document

Document ID: 3141099
Creation Date: 02-14-2007
Modified Date: 12-24-2008
Novell Product: SUSE Linux Enterprise Desktop
Novell Product: SUSE Linux Enterprise Server

mount in chroot environment not possible

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Having a problem logging in? Please visit this page to clear all LQ-related cookies. Old 12-05-2004, 02:39 PM   #1 moskito01

LQ Newbie

Registered: Jun 2004

Posts: 22

mount in chroot environment not possible

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Hi,

I am trying to clone a running Suse 9.2 system.

Back with Suse 8.2 all I had to do was:
1.) copy / to the new location
2.) add a new entry for the cloned system in /boot/grub/menu.lst
3.) chroot to the cloned system
4.) modify /etc/fstab of the cloned system
5.) mount /boot Partition
6.) create a new initrd
7.) exit chroot and reboot
-> works

At Suse 9.2 step 5.) does not work.

venus:/# mount -t ext3 /dev/hda5 /boot
mount: special device /dev/hda5 does not exist

Displaying /dev shows that /dev/hda5 is non-existent

venus:/# ls /dev
. .. .udev.tdb null
venus:/#

I suppose this is because udev is not running in chroot-Environment...but how can i start it manually?
What about sysfs - i read somewhere that sysfs is needed by udev - do i have to start sysfs too?

Thanks in advance for the help    
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Old 12-05-2004, 02:57 PM   #2
mikeyt_333

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what does fdisk's partition table say about your /dev/hda?

     
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Old 12-06-2004, 03:48 AM   #3
abisko00

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Registered: Mar 2004

Location: Munich

Distribution: SuSE 11.2

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Maybe this is easier if you'd use a distro that also uses udev, e.g. KNOPPIX with kernel 2.6

     
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Old 12-06-2004, 03:04 PM   #4
moskito01

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Registered: Jun 2004

Posts: 22

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Original Poster  

my partition table:
-------------------

Device Boot Start End Blocks Id System
/dev/hda1 * 1 26902 13558576+ 7 HPFS/NTFS
/dev/hda2 146041 155055 4543560 12 Compaq diagnostics
/dev/hda3 26903 146040 60045552 f W95 Ext'd (LBA)
/dev/hda5 92439 92601 82120+ 83 Linux
/dev/hda6 26903 47708 10486161 83 Linux
/dev/hda7 92602 95722 1572952+ 82 Linux swap / Solaris
/dev/hda8 95723 116528 10486192+ 83 Linux
/dev/hda9 47709 58111 5243080+ 8e Linux LVM
/dev/hda10 58112 80997 11534512+ 8e Linux LVM

Partition table entries are not in disk order

-> the system i want to clone resides on /dev/hda6
-> target for clonig ist /dev/hda10 (via LVM2)


The Suse 9.2 from which i try to do the cloning also uses udev, so why should i switch to KNOPPIX 2.6?

I tried the steps with KNOPPIX 2.6 but did not manage to load LVM-Module.
Is dm_mod (LVM2) not included in KNOPPIX 2.6?

     
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Old 12-06-2004, 03:08 PM   #5
electronique

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before you chroot try
mount -o bind /dev /dir/of/new/dev

that command I had to use when installing Gentoo linux in order to get it to properly read my Promise FastTrack Raid chips.

for instance

mount -o bind /dev /mnt/gentoo/dev

and then

chroot /bin/bash

     
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Old 12-06-2004, 04:06 PM

moskito01

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Original Poster  

thanks, that worked!

but now i ran in a new problem.
I built the new initrd and rebooted.
The cloned system starts, all the messages rush by - i can't see errors - perhaps because my eyes are too slow
I can see loading of lvm modules as well as filesystem modules (reiser, ext3)...
After loading of USB-Driver (before init starts) something like

md: stopping all md devices appears
md: restarting system

i have no chance to really check the startup output for errors...
i don't use md at all ?! so can't imagine what that means...

Any ideas?



Etc

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