On Thu, May 27, 2010 at 04:33:48PM -0400, Andrew Lutomirski wrote:
> # touch foo
> # touch bar
> # mount -n --bind foo bar
> # mount -n -o remount,ro bar
> mount: can't find bar in /etc/fstab or /etc/mtab
>
> That seems like an oversight -- why is -o remount looking at
> /etc/fstab and /etc/mtab at all? Especially when I set -n.
The syscall requires mount source and target, you have specified
'bar', that's ambiguous request. Man mount:
The remount functionality follows the standard way how the mount
command works with options from fstab. It means the mount
command doesn’t read fstab (or mtab) only when a device and dir
are fully specified.
> There are a few ways I can think of to fix this:
>
> 1. Make mount -n (or mount --use-proc) look at /proc/self/mounts
> instead of /etc/mtab.
The /proc does not contain all necessary information. For example
'bind' flag is not stored there. It means that for the read-only bind
remount you have to explicitly use --bind option.
If you have a system with /etc/mtab then mount(8) is able to read the
'bind' flag from the file.
> 2. Make mount -n -o remount not care about mtab and just issue the syscall.
It works, you have to specify all necessary information on command
line, it means:
mount -o remount,for,bar <source> <target>
On Thu, May 27, 2010 at 04:57:27PM -0400, Andrew Lutomirski wrote:
> This works:
>
> # mount -n --bind -o remount,ro none bar
>
> Perhaps that should go in the man page. This isn't intuitive at all.
I'll add a note to the man page that --bind is required for the remount
on systems without /etc/mtab.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
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