[closed] chroot questions, mount point proc/ does not exist [restored]

sotu · 2012-02-12 04:18:24

Hi All,

recently I experienced what seems to be a moderately frequent issue: I updated my kernel and on next boot got the error about ERROR: unable to determine major/minor number of root device

found that the best way to fix this is to chroot to my existing arch system using another linux cd (I chose to simply use Arch live boot because I have the ISO sitting on my desktop) and then downgrade the kernel to previously good/known working version.

So that is what I am working on and I have this wiki page (https://wiki.archlinux.org/index.php/Change_Root) about change root that is a good guide.

Here is my quesiton
1.) I booted arch live from iso
2.) mkdir for /mnt/arch
3.) mount /dev/<device-or-partition-name> /mnt/arch

I mounted my /dev/sda1 because that is what the boot star is next too (presumably that means its where the system kernel is? I am a little shaky on this)

Then after mounting it I try to do the
cd /mnt/arch
mount -t proc proc proc/

and get that mount point proc/ does not exist. I make an ls and sure enough there is no proc/ (I am wondering maybe if I mounted the wrong device??

Here is a screen shot of my device table after I fdisk -l |less - http://i.imgur.com/3DdSm.png

Can someone provide advice as to whether I mounted the correct device from that screen shot and/or if the proc/ folder is missing what does that mean?

Sorry but the chroot wiki is either not informative enough or I am just too new.

Thanks!
sotu

Last edited by sotu (2012-02-12 19:25:11)

jasonwryan · 2012-02-12 04:34:31

Please resize your screenshot to conform with the Forum guidelines.

It looks like you are running LVM: have you prepped the volume group prior to mounting?

sotu · 2012-02-12 05:07:53

thanks for the tip I removed the image and will just leave the link to it on the hosting site.

I did not see a section on the chroot wiki about prepping the vol group prior to mounting so I didnt do this. I searched for "prep" on that page to be certain i didnt overlook it but nothing shows.

I did search a little bit more on the forum for 'lvm prep volume group' but I'm not really finding information that seems relevant. Could you maybe elaborate a bit for me on that? OR link to more info? Thanks very much

jasonwryan · 2012-02-12 06:44:00

You need to make the volumes available. The info is in man vgchange. Basically, you issue:

vgchange --available y <nameofgroup>

You can then check that it is all prepped with:

vgdisplay

sotu · 2012-02-12 17:28:29

Thanks for pointing me to vgchange, took a look at the man page. I'm wondering if you can give me some info on how to determine the name of the volume group? I tried /dev/sda1 but that returned no volume found

The man page says I can run

 vgchange -a y

to prep all volume groups but this also just returns

No volume groups found

Also, on the wiki page for LVM https://wiki.archlinux.org/index.php/LVM I found that you should check the System column of the

fdisk -l

for Linux LVM to determine if it is Linux LVM. In my screen shot this column only says Linux. Do you think that it is still using Linux LVM given this?

From the wiki:

Now you need to initialize these partitions so they can be used by LVM. Use fdisk -l to find out which partitions have filesystem type 'Linux LVM' and create a physical volume on them:

Last edited by sotu (2012-02-12 17:32:24)

sotu · 2012-02-12 17:40:41

Possibly getting a head of myself but I went ahead and ran

vgcreate VolGroup00 /dev/sda1

Then I ran

vgdisplay

and I see the Volume Group VolGroup00 with Format lvm2 and some other info. Lastly I tried

mount /dev/sda1 /mnt/arch

which previously mounted the volume but did not include the proc/ folder, no I receive the message

mount: unknown filesystem type 'LVM2_member'

No luck still

Last edited by sotu (2012-02-12 17:41:38)

HalfEmptyHero · 2012-02-12 18:54:07

You shouldn't have ran vgcreate VolGroup00 /dev/sda1, that created a logical volume over /dev/sda1. I don't know enough about lvm to know how much damage that did.

Looking at your image, /dev/sda1 looks like /boot judging by the size of it. Maybe /dev/sda3 is root partition and /dev/sda4 is the home partition. If that is the case, you can mount /dev/sda3 to /mnt/arch then mount /dev/sda1 into /mnt/arch/boot. After that chroot into /mnt/arch and then run mount -t proc proc /proc.

sotu · 2012-02-12 19:11:08

That was really helpful thank you! So far I think I've gotten a lot farther I was able to mount everything up until mounting sda1 to /boot. As you mentioned probably vgcreate VolGroup00 /dev/sda1 marked the volume as LVM2_Member because previously I could mount it and now I can not. When I try to mount it to boot I get

unknown filesystem type 'LVM2_member'

I think I need to somehow undo whatever was marked by the vgcreate that I did. I am not sure what my options are here so if anyone has any idea's that would be great. I found some articles online about it but mostly just seem to say "restored to a backup" unfortunately I didn't make a backup before creating the volume.. I suppose I wasnt careful enough, but I will see if undoing it is possible.

sotu · 2012-02-12 19:24:48

to anyone who finds this thread in the future,

I think these will help you:
http://pissedoffadmins.com/?p=481
http://www.fedoraforum.org/forum/archiv … 64964.html

I cant post a solution because I ended up restoring my VM to a previous snapshot (I was fortunate enough to back up the whole VM before pacman -Syu updated the kernel and started this whole mess)

Thanks to everyone who tried to help in this case. As a warning, if you are going to chroot using the wiki DO NOT do what jasonwryan suggest above and "prep the volume" by creating logical groups. Once your device is marked/becomes lvm2_member you can not mount it. I'm sure jasonwryan is right that this could be necessary for other things but his statement 'It looks like you are running LVM:' might have just been a step in the wrong direction from the start (no fault of his)

Last edited by sotu (2012-02-12 19:25:57)

fsckd · 2012-02-12 21:54:18

Hi, can you change it from [closed] to [solved]? It may confuse others as closed threads are ones where users are no longer allowed to post.
Thanks.

Arch Linux

#1 2012-02-12 04:18:24

[closed] chroot questions, mount point proc/ does not exist [restored]

#2 2012-02-12 04:34:31

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#3 2012-02-12 05:07:53

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#4 2012-02-12 06:44:00

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#5 2012-02-12 17:28:29

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#6 2012-02-12 17:40:41

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#7 2012-02-12 18:54:07

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#8 2012-02-12 19:11:08

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#9 2012-02-12 19:24:48

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

#10 2012-02-12 21:54:18

Re: [closed] chroot questions, mount point proc/ does not exist [restored]

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