Use SSHFS on XenServer 6.1

backupsshfsvirtual-machinesxen

On Xen Server 6.1, to backup my VMs, I use a script based on the following tools:

  • xe vm-list to build a list of the VMs to backup
  • xe vm-snapshot to take a snapshot of the VMs
  • xe template-param-set is-a-template=false ha-always-run=false to convert the snapshot to a VM
  • xe vm-export vm=uuid_of_this_new_vm filename=|ssh ..... "cat > /path/backup.xva"
    –> To send the export to my backup server without to store it locally
  • xe vm-uninstall

I'd like to use sshfs to mount my remote backup server on my Xen host. But sshfs is not available in the Xen distribution or the default repository (XenServer 6.1.0 updates).

I have a few possibilities to install sshfs on my Xen host:

  • I add a repo that contains sshfs. I think it could cause me troubles later. It's not supported by Xen and I prefer to let the host config mostly unchanged
  • I could take a tarball and install it in a directory apart
  • or I take a RPM and install it apart

OR I find a way to pipe a remote ssh command into xe vm-import like I do for the export. I tested a lot of things but nothing that works

What would be the best solution in your opinion?

Best Answer

Although this is an old question, I have just figured this one out myself.

First.. what DOES NOT WORK (All tested on XenServer 6.5):

xe-import filename=/dev/stdin does not work.. at all. It does not matter whether you do:

# simple local import on xenhost
xe vm-import filename=/dev/stdin < myexport.xva

# try it the other way, with cat, still won't work:    
cat myexport.xva | xe vm-import filename=/dev/stdin

# and no, dd instead of cat in the above does not make it better

# nor can you pull the file from elsewhere via ssh:
ssh user@backupserver "cat myexport.xva" |  xe vm-import filename=/dev/stdin

# nor the other way, pushing from elsewhere to your xenserver
ssh root@xenhost "xe vm-import filename=/dev/stdin" < myexport.xva

# named pipes don't work either, even locally:
mkfifo mypipe
cat myexport.xva > ./mypipe &
xe vm-import filename=./mypipe

So, what I have found is that there is no way to import from a stream, it has to be a real filesystem of some sort. Apparently this used to work, but it doesn't now. My guess is that xenserver wants to seek.

(If anyone can spot a flaw in my attempts and prove me wrong, I'd be very grateful).

So, yes, my conclusion is that you must use a remote filesystem, and we know that NFS works for this, because we've used it.. but decided on sshfs for simplicity. Here is how I installed sshfs on XenServer 6.5:

# fuse-fs and fuse-libs are in existing repos, so..
yum --enablerepo=base --disablerepo=citrix install fuse-fs
# for some reason yum wanted to install i386 fuse-libs which fails
# because of a dependency on i386 glibc.. nevermind all that, tell it
# directly that we want x86_64 and it will work:
yum --enablerepo=base --disablerepo=citrix install fuse-libs.x86_64

# fuse-sshfs is in the epel repo, which we need to add
yum --disablerepo=citrix --enablerepo=extras install epel-release
# now install fuse-sshfs
yum --disablerepo=citrix --enablerepo=extras install fuse-sshfs

# The above leaves epel-release enabled, which should be no problem but
# nevertheless I disabled it since I don't need it anymore:
#   Use vim to edit /etc/yum.repos.d/epel.repo
#   Where it says `enabled=1` change to `enabled=0`
vim /etc/yum.repos.d/epel.repo

Ok now to restore from an export on another machine:

# make mount point
mkdir backups

# mount location of your backups onto mount point
sshfs user@backupserver.mydomain.com:/path/to/backups backups

# import as usual
xe vm-import filename=backups/myexport.xva

# unmount the remote filesystem, if you don't need it anymore
umount backups

# IT WORKS

Oh, and I should add.. I tried installing the xenxerver tools on our backup server.. it does not work either. Sure, you can execute commands and it all looks great. But filename=/dev/stdin still does not work, NOR DOES filename=/path/to/myexport.xva. It just hangs or starts importing then fails in weird ways.

So that's importing.. but what about exporting? Using the xenserver tools remotely installed:

xe vm-export uuid=the-vm-uuid filename= -s xenhost.my.domain -u root -pwf password_file

This DOES export to stdout. But it's a bit unclear as to whether those exports will always import successfully. I experienced a couple of failures and some successes. SO decided against using remote tools at all.. but do it via ssh instead:

ssh root@xenhost.my.domain "vm-export uuid=the-vm-uuid filename=" > myexport.xva

IT WORKS!

The upshot of this is that, with our backup system (Bareos) it is possible to do a backup via ssh directly into the backup software, without having to do an export to a temporary file first. But to do the restore, it is necessary to restore the xva to a temporary storage first, then mount on the xenhost with sshfs, then vm-import. I am sad that we can't stream both ways.. hopefully this will be fixed in xe some time.

Hope this helps some people.. it took a good amount of trial and error to test all the possibilities :)

Related Topic