two root entries in /proc/mounts, neither in fstab?

drwook · Veteran Joined: 30 Mar 2005 Posts: 1324 Location: London

hey guys,

Well this has confused me, at the top of /proc/mounts (and /etc/mtab) I've got this;

Cazzantonio · Posted: Sun Apr 20, 2008 6:34 pm Post subject:

I have the same problem, but it is an opernc/baselayout-2 issue since it happened after that upgrade.
It isn't an udev issue since a similar installation with same udev and stable baselayout doesn't have two root mounted.
_________________
Any mans death diminishes me, because I am involved in Mankinde; and therefore never send to know for whom the bell tolls; It tolls for thee.
-John Donne

enito · Tux's lil' helper Joined: 10 Oct 2005 Posts: 79

Hi, any way for fix this? i tryed manualy edit mtab and delete dupped / and setup correctly, but when you reboot , all back again, duped entry...thx

Dairinin · n00b Joined: 03 Feb 2008 Posts: 64 Location: MSK, RF

Looks like a new "feature" to me. Had to change "/dev/sdb6" to "/dev/root" in cacti data source.

uzz75 · n00b Joined: 29 Aug 2005 Posts: 34 Location: Italy

I don't think it's from udev

# cd /etc/udev/
# grep rootfs * -R
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Michele

Dairinin · n00b Joined: 03 Feb 2008 Posts: 64 Location: MSK, RF

It's here:
/lib64/udev/write_root_link_rule

called from /lib/rcscripts/addons/udev-start.sh

enito · Tux's lil' helper Joined: 10 Oct 2005 Posts: 79

and how we can disable this new feature?

greets

ABCDwp · Retired Dev Joined: 26 Mar 2006 Posts: 79

The actual change is that baselayout-2/openrc copies /proc/mounts onto /etc/mtab during boot - it does so, so that the mount table in /etc/mtab is correct (/proc/mounts is what the kernel actually mounted - not what you thought you mounted). The /dev/root symlink is so that things make a little more sense to the average end-user, but is unneeded - the kernel will call the initramfs "rootfs" and the root=/dev/XYZ parameter "/dev/root" no matter what you do (IIRC).

drwook · Veteran Joined: 30 Mar 2005 Posts: 1324 Location: London

The Unknown · Posted: Mon Apr 21, 2008 7:11 am Post subject:

This is not new, I have stable systems with the old baselayout and its the exact same.
Your not really double mounting root either. This quote is from some kernel documentation

Quaoar · n00b Joined: 13 Jan 2008 Posts: 10

but this "feature" definitely hit me with baselayou2/openrc - never had this before and I still don't have it on the baselayout1-machines.

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

I had googled about this quite a while ago. From my memory, these were the results:
baselayout-1 was once artificially modified to remove rootfs.
openrc wants to be more conformal to the standard (e.g. it should not run only under gentoo) and since some scripts out there rely on /dev/root, openrc makes no attempt to "hide" this filesystem.

Cazzantonio · Posted: Mon Apr 21, 2008 1:56 pm Post subject:

I understand that this rootfs, mounted "below" the standard /dev/root, is something that the kernel does independently of openrc.
/proc/mounts lists correctly this rootfs with or without openrc. What openrc does is exactly copying all entries from /proc/mounts in /etc/mtab, so that's why this rootfs appears with baselayout-2.

What I don't really understand is what this rootfs really is. During the boot process root get mounted readonly and then remounted rw. This rootfs isn't the first mount of the root filesystem, since it is mounted rw. Also the rw remount should be made with "mount -o remount", which won't mount /dev/root above the old mount.

rootfs is present in ubuntu too so it isn't something gentoo-specific.

Can anyone explain me what rootfs is and what is there for?
_________________
Any mans death diminishes me, because I am involved in Mankinde; and therefore never send to know for whom the bell tolls; It tolls for thee.
-John Donne

Desintegr · Posted: Mon Apr 21, 2008 10:43 pm Post subject:

Another problem : options in /etc/fstab are not respected :

/etc/fstab :

ABCDwp · Retired Dev Joined: 26 Mar 2006 Posts: 79

Desintegr · Posted: Tue Apr 22, 2008 2:29 pm Post subject:

Just after boot :

BitJam · Posted: Thu May 26, 2011 12:58 am Post subject:

I've run into this too after upgrading to baselayout-2. I don't mind the two / entries so much, what seems broken to me is that the device that is actually mounted at / no longer shows up in the output of df:

krinn · Watchman Joined: 02 May 2003 Posts: 7470

it's an old thing : https://forums.gentoo.org/viewtopic-p-6204542-highlight-rootfs.html#6204542
and the new openrc (it wasn't doing it by this time) now auto mount itself shm (you can check it with mount)

So if anyone wish to disable the rootfs he should hack sysfs to remove shm mount and this should remove rootfs (as this user was doing by this time, when openrc wasn't mounting shm, we were ask to add that in fstab)
shm /dev/shm tmpfs nodev,nosuid,noexec 0 0

dunno if this work to just disable shm fs mount, AND, more dunno how your system will play if you do that.
as it's the new "standard" i can just tell you that you shouldn't disable it, as some new tools might use and expect its presence (and specially as it was add by kernel at first)

theBlackDragon · l33t Joined: 23 Nov 2002 Posts: 768 Location: Belgium

I've run into this as well now, so should I replace the direct link to my root partition with /dev/root ?

Right now I get this: