Hi Frans! Let's see whether I can explain this (I'm not a guru...) On 11 Nov 2007, at 11:06, Frans Pop wrote:
I'm not sure whether this is a bug or expected behavior. Suppose I create a "looped" bind mount situation as follows. # mkdir test # touch test/foo # mkdir bindtest # touch bindtest/bar # mkdir bindtest/test # mount --bind test/ bindtest/test/ # ls bindtest/test/ foo # mount --bind bindtest/ test/
This mounts the bindtest/ tree on test/ _without_ copying the mount points which are found on subtrees. This is necessary to avoid loops in the filesystem (bind mounts are somewhat like hardlinks on directories, just without the headaches).
This lists the contents of the original bintest/test/ directory which you created above. Creating e.g. a file in there stores that file physically in bindtest/test/bla, where "test" does _not_ mean the bind mount but the underlying directory here.# ls test/ bar test # ls test/test/ #
I'd expected the last command to list "foo", but it shows an empty dir. Shouldn't it also show the original contents of test (as they were beforeYou see, the bindtest/test/ mount was not propagated to test/test/. This is very much by design. You can e.g. dothe first bind mount)? # mount | grep test /root/test on /root/bindtest/test type none (rw,bind) /root/bindtest on /root/test type none (rw,bind)
# mkdir -p test/test # mount --bind test test/test # ls test/test test # ls test/test/test #so there is no loop (`find test` would actually say that it terminates because it has detected a loop, so it cannot be used to test this).
# touch test/test/test/a # ls test/test/test a # ls test/test # umount test/test # ls test/test a #So, you see, test/test/test/a was (as it should) physically created in test/test, where it is shadowed by the bind mount as long as that is not removed. Nothing vanishes into "thin air" ;-)
Ciao, Roland -- TU Muenchen, Physik-Department E18, James-Franck-Str., 85748 Garching Telefon 089/289-12575; Telefax 089/289-12570 -- CERN office: 892-1-D23 phone: +41 22 7676540 mobile: +41 76 487 4482 -- Any society that would give up a little liberty to gain a little security will deserve neither and lose both. - Benjamin Franklin -----BEGIN GEEK CODE BLOCK----- Version: 3.12GS/CS/M/MU d-(++) s:+ a-> C+++ UL++++ P+++ L+++ E(+) W+ !N K- w--- M + !V Y+
PGP++ t+(++) 5 R+ tv-- b+ DI++ e+++>++++ h---- y+++ ------END GEEK CODE BLOCK------
Attachment:
PGP.sig
Description: This is a digitally signed message part
- Follow-Ups:
- Re: Bind mount bug?
- From: Frans Pop <[email protected]>
- Re: Bind mount bug?
- References:
- Bind mount bug?
- From: Frans Pop <[email protected]>
- Bind mount bug?
- Prev by Date: Re: 2.6.24-rc2 STD with s2disk fails to activate suspended system after loading
- Next by Date: Re: 2.6.24-rc2: Reported regressions from 2.6.23 (updated)
- Previous by thread: Re: Bind mount bug?
- Next by thread: Re: Bind mount bug?
- Index(es):