Dave Miller wrote:
Jim Kissel wrote on 12/11/07 6:47 AM:
Is it possible using unionfs to mount an directory from one of these
external sources such that it forms a union with /bin that is
transparent to the user? I would like to do similar with /lib
A program on /media/external_dirve/bin would appear to be in /bin and if
it needs any additional libraries, the ones stored on
media/external_drive/lib would appear in /lib
Based on a recent conversation in #unionfs on freenode that I saw, I'm
pretty sure this is possible (but I haven't tried it myself, so this is
just hearsay :) ). The trick is you need to bind mount /bin and /lib
somewhere else first and use the bind-mounted copies as the branches in
your unionfs mounts (which you would then mount overtop of the original
locations).
mkdir /mnt/fakebin
mount --bind /bin /mnt/fakebin
mkdir /mnt/fakelib
mount --bind /lib /mnt/fakelib
mount -t unionfs -o dirs=/media/external_drive/bin=rw:/mnt/fakebin=ro \
unionfs /bin
mount -t unionfs -o dirs=/media/external_drive/lib=rw:/mnt/fakelib=ro \
unionfs /lib
Great idea, but......
/bin is already a part of a union that is mounted a /
The --bind works, but unionfs (2.0) prevents you from creating a union
of /media/external_drive.... and /mnt/fakebin with a:
mount: wrong fs type, bad option, bad superblock on unionfs,
missing codepage or other error
In some calse useful info is found in syslog - try
dmesg | tail or so
which yields:
unionfs: hidden directory '/home/user/MMc-SD/partition1/bin is not a
valid branch
unionfs_read_super: error while parsing options (err = -22)
I've also tried with /fakebin on the same disk as /bin and used the
option 'none' instead of 'unionfs' Same results in both cases.
Thanks for you feedback. I thought you had solved it. I may have to
abandon unionfs for now until the unionfs-odf is stable.
kind regards
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