loop device with sparse file on NTFS over Samba

[sqcomic]

I'm trying to backup my linux server to a remote computer - but the remote computer is running windows. So I set up a sparse file on an NTFS drive, built and ext3 filesystem on it, and mount it as a loop device over samba. It appears to work - it gives no errors and lets me add and delete files and folder. But after unmounting and remounting the device, most often it reverts back to the way it was right after mounting it the last time - new files created are not there, and files that were deleted are still there.

Does anyone have any idea what is going on? Is there something that I need to flush when I unmount? To mount and unmount I use the following code:

To Mount:
mount -t smbfs //RemoteWindowsMachine/RemoteFolder /mnt/backupsamba
losetup /dev/loop0 /mnt/backupsamba/BackupExt2.img
mount -t ext3 /dev/loop0 /mnt/remotebackup

To Unmount:
umount /mnt/remotebackup
losetup -d /dev/loop0
umount /mnt/backupsamba

Thanks!

[Rubberman]

First, use the cifs file system, instead of smbfs when mounting a windows share. It is more up-to-date and reliable. Second, you might need to sync your file systems before running [I][osetup -d /dev/loop0/I] - I'm not sure it writes buffered data before closing it down. Third, you might try creating the BackupExt2.img file (presize it with dd if=/dev/zero of=/mnt/backupsamba/BackupExt2.img count=numblocks first, then format it with mkfs -t type /dev/loop0, then mount it with mount -t type /dev/loop0 mount-point. You should then be able to write your data to the mount-point. Here is a section of the losetup man page that addresses this:

       The following commands can be used as an example of using the loop device.

              # dd if=/dev/zero of=/file bs=1k count=100
              # losetup -e des /dev/loop0 /file
              Password:
              Init (up to 16 hex digits):
              # mkfs -t ext2 /dev/loop0 100
              # mount -t ext2 /dev/loop0 /mnt
               ...
              # umount /dev/loop0
              # losetup -d /dev/loop0

It shows using an encrypted volume, which you don't need to do, but it may be useful for security purposes.

[sqcomic]

Thanks for the advice. I had created the file in a similar manner - I did it on the windows machine using cygwin. I made a sparse file, however - so maybe there's some conflict there. I formatted it using mke2fs.

I tried using cifs, but I get the same results - I can mount it, add files, delete file, but then when I unmount and remount, some of the files are gone, and some that should be gone because I deleted them are still there ???

Anyone have any idea what's up?

[Rubberman]

Did you sync before unmounting the volumes (loop and cifs)?

[sqcomic]

I had assumed that umount would sync before unmounting - I've never had problems mounting and unmounting filesystems before. But it looks like running sync before unmounting the loopback device does the trick. I think that solved the problem. Thanks a ton!

[Rubberman]

I think there were just too many levels of redirection here. If you unmount hardware devices, then they get sync'd. However, if you unmount a loop device I'm not so sure. As the old saying goes, better safe than sorry!