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* Mount -a and bind mounts. Bug?
@ 2011-12-09 12:33 Andrew Walrond
  2011-12-09 12:48 ` Karel Zak
  2011-12-09 12:50 ` Andrew Walrond
  0 siblings, 2 replies; 7+ messages in thread
From: Andrew Walrond @ 2011-12-09 12:33 UTC (permalink / raw)
  To: util-linux

When using bind mounts, particularly when they are specified in /etc/fstab, 'mount -a' does not recognise that a mount is already mounted and will rebind another copy over the top with each mount -a.

Is this the expected behaviour? I'm not sure so I thought I'd ask.
I'm using v2.20.1.

Example:

user@localhost ~ $ cat /etc/fstab 
#FILESYSTEM          MOUNTPOINT  TYPE     OPTIONS      BACKUP FSCK-PASS
/root/etc            /etc        none     bind         0      0
/root/home           /home       none     bind         0      0
/root/local          /local      none     bind         0      0
/root/mnt            /mnt        none     bind         0      0
/root/tmp            /tmp        none     bind         0      0
/root/var            /var        none     bind         0      0
/root/swap            none       swap     sw           0      0

user@localhost ~ $ mount
rootfs on / type rootfs (rw,size=0k,nr_inodes=0)
none on /dev type devtmpfs (rw,relatime,size=7202028k,nr_inodes=1800507,mode=755)
none on /proc type proc (rw,relatime)
none on /sys type sysfs (rw,relatime)
none on /dev/pts type devpts (rw,relatime,gid=3,mode=620)
none on /dev/shm type tmpfs (rw,relatime)
/dev/vda on /root type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /etc type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /home type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /local type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /mnt type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /tmp type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /var type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)

user@localhost ~ $ sudo mount  -a

user@localhost ~ $ mount
rootfs on / type rootfs (rw,size=0k,nr_inodes=0)
none on /dev type devtmpfs (rw,relatime,size=7202028k,nr_inodes=1800507,mode=755)
none on /proc type proc (rw,relatime)
none on /sys type sysfs (rw,relatime)
none on /dev/pts type devpts (rw,relatime,gid=3,mode=620)
none on /dev/shm type tmpfs (rw,relatime)
/dev/vda on /root type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /etc type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /home type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /local type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /mnt type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /tmp type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /var type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /etc type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /home type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /local type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /mnt type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /tmp type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)
/dev/vda on /var type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered)

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: Mount -a and bind mounts. Bug?
  2011-12-09 12:33 Mount -a and bind mounts. Bug? Andrew Walrond
@ 2011-12-09 12:48 ` Karel Zak
  2011-12-09 12:55   ` Andrew Walrond
  2011-12-09 12:50 ` Andrew Walrond
  1 sibling, 1 reply; 7+ messages in thread
From: Karel Zak @ 2011-12-09 12:48 UTC (permalink / raw)
  To: Andrew Walrond; +Cc: util-linux

On Fri, Dec 09, 2011 at 12:33:58PM +0000, Andrew Walrond wrote:
> When using bind mounts, particularly when they are specified in
> /etc/fstab, 'mount -a' does not recognise that a mount is already
> mounted and will rebind another copy over the top with each mount
> -a.
> 
> Is this the expected behaviour? I'm not sure so I thought I'd ask.
> I'm using v2.20.1.

 - distro?
 - linked with libmount?
 - do you have regular mtab or symlink to /proc/mounts
 
-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: Mount -a and bind mounts. Bug?
  2011-12-09 12:33 Mount -a and bind mounts. Bug? Andrew Walrond
  2011-12-09 12:48 ` Karel Zak
@ 2011-12-09 12:50 ` Andrew Walrond
  1 sibling, 0 replies; 7+ messages in thread
From: Andrew Walrond @ 2011-12-09 12:50 UTC (permalink / raw)
  To: util-linux

In case it's relevant - /etc/mtab is a symlink to /proc/mounts.

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: Mount -a and bind mounts. Bug?
  2011-12-09 12:48 ` Karel Zak
@ 2011-12-09 12:55   ` Andrew Walrond
  2011-12-09 13:01     ` Karel Zak
  0 siblings, 1 reply; 7+ messages in thread
From: Andrew Walrond @ 2011-12-09 12:55 UTC (permalink / raw)
  To: Karel Zak; +Cc: util-linux

On Fri, Dec 09, 2011 at 01:48:37PM +0100, Karel Zak wrote:
> On Fri, Dec 09, 2011 at 12:33:58PM +0000, Andrew Walrond wrote:
> >
> > I'm using v2.20.1.
> 
>  - distro?

A custom job of my own

>  - linked with libmount?

Don't think so.

$ ldd /bin/mount
        linux-vdso.so.1 =>  (0x00007fff093af000)
        libblkid.so.1 => //lib/libblkid.so.1 (0x00007f087b755000)
        libuuid.so.1 => //lib/libuuid.so.1 (0x00007f087b551000)
        libc.so.6 => //lib/libc.so.6 (0x00007f087b1ca000)
        /lib64/ld-linux-x86-64.so.2 => //lib64/ld-linux-x86-64.so.2 (0x00007f087b97b000)

Saw some mention of libmount somewhere when I upgraded and built 2.20.1 but didn't have time to read further.
What's the current recommendation? Should I link against it?

>  - do you have regular mtab or symlink to /proc/mounts

symlink to /proc/mounts


Andrew Walrond

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: Mount -a and bind mounts. Bug?
  2011-12-09 12:55   ` Andrew Walrond
@ 2011-12-09 13:01     ` Karel Zak
  2011-12-09 13:03       ` Karel Zak
  0 siblings, 1 reply; 7+ messages in thread
From: Karel Zak @ 2011-12-09 13:01 UTC (permalink / raw)
  To: Andrew Walrond; +Cc: util-linux

On Fri, Dec 09, 2011 at 12:55:37PM +0000, Andrew Walrond wrote:
> On Fri, Dec 09, 2011 at 01:48:37PM +0100, Karel Zak wrote:
> >  - distro?
> 
> A custom job of my own
> 
> >  - linked with libmount?
> 
> Don't think so.
> 
> $ ldd /bin/mount
>         linux-vdso.so.1 =>  (0x00007fff093af000)
>         libblkid.so.1 => //lib/libblkid.so.1 (0x00007f087b755000)
>         libuuid.so.1 => //lib/libuuid.so.1 (0x00007f087b551000)
>         libc.so.6 => //lib/libc.so.6 (0x00007f087b1ca000)
>         /lib64/ld-linux-x86-64.so.2 => //lib64/ld-linux-x86-64.so.2 (0x00007f087b97b000)
> 
> Saw some mention of libmount somewhere when I upgraded and built 2.20.1 but didn't have time to read further.
> What's the current recommendation? Should I link against it?
> 
> >  - do you have regular mtab or symlink to /proc/mounts
> 
> symlink to /proc/mounts

 ... okay then it's expected behavior. The file /proc/mounts does not
 provide enough information about bind mounts. You need regular mtab
 or link with libmount (the library reads /proc/self/mountinfo and
 does some horrible voodoo to detect already mounted bind mounts).

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: Mount -a and bind mounts. Bug?
  2011-12-09 13:01     ` Karel Zak
@ 2011-12-09 13:03       ` Karel Zak
  2011-12-09 13:15         ` Andrew Walrond
  0 siblings, 1 reply; 7+ messages in thread
From: Karel Zak @ 2011-12-09 13:03 UTC (permalink / raw)
  To: Andrew Walrond; +Cc: util-linux

On Fri, Dec 09, 2011 at 02:01:28PM +0100, Karel Zak wrote:
> On Fri, Dec 09, 2011 at 12:55:37PM +0000, Andrew Walrond wrote:
> > On Fri, Dec 09, 2011 at 01:48:37PM +0100, Karel Zak wrote:
> > >  - distro?
> > 
> > A custom job of my own
> > 
> > >  - linked with libmount?
> > 
> > Don't think so.
> > 
> > $ ldd /bin/mount
> >         linux-vdso.so.1 =>  (0x00007fff093af000)
> >         libblkid.so.1 => //lib/libblkid.so.1 (0x00007f087b755000)
> >         libuuid.so.1 => //lib/libuuid.so.1 (0x00007f087b551000)
> >         libc.so.6 => //lib/libc.so.6 (0x00007f087b1ca000)
> >         /lib64/ld-linux-x86-64.so.2 => //lib64/ld-linux-x86-64.so.2 (0x00007f087b97b000)
> > 
> > Saw some mention of libmount somewhere when I upgraded and built 2.20.1 but didn't have time to read further.
> > What's the current recommendation? Should I link against it?
> > 
> > >  - do you have regular mtab or symlink to /proc/mounts
> > 
> > symlink to /proc/mounts
> 
>  ... okay then it's expected behavior. The file /proc/mounts does not
>  provide enough information about bind mounts. You need regular mtab
>  or link with libmount (the library reads /proc/self/mountinfo and
>  does some horrible voodoo to detect already mounted bind mounts).

 see also:

 http://karelzak.blogspot.com/2011/04/bind-mounts-mtab-and-read-only.html

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: Mount -a and bind mounts. Bug?
  2011-12-09 13:03       ` Karel Zak
@ 2011-12-09 13:15         ` Andrew Walrond
  0 siblings, 0 replies; 7+ messages in thread
From: Andrew Walrond @ 2011-12-09 13:15 UTC (permalink / raw)
  To: Karel Zak; +Cc: util-linux

On Fri, Dec 09, 2011 at 02:03:05PM +0100, Karel Zak wrote:
> 
>  http://karelzak.blogspot.com/2011/04/bind-mounts-mtab-and-read-only.html
> 

Nice blog entry, made incidentally on my birthday which is obviously how I missed it ;)

My build script now contains --enable-libmount-mount. Thanks for your time!

Andrew Walrond

^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2011-12-09 13:15 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-12-09 12:33 Mount -a and bind mounts. Bug? Andrew Walrond
2011-12-09 12:48 ` Karel Zak
2011-12-09 12:55   ` Andrew Walrond
2011-12-09 13:01     ` Karel Zak
2011-12-09 13:03       ` Karel Zak
2011-12-09 13:15         ` Andrew Walrond
2011-12-09 12:50 ` Andrew Walrond

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