[mythtv-users] Diskless Front End (again)
mythtv-users at moley.org.uk
Thu May 3 10:41:59 UTC 2007
Rich West wrote:
> My understanding is that the idea is supposed to be that you have one
> _generic_ image for your hosts, and the configuration files are the ones
> that are symbolically linked off to the individual snapshots for each of
> the hosts. This way, you just have one image to deal with, and, when
> you do updates, you do them via the server and chroot to the diskless
> environment (as you said). The configuration files will get updated,
> but only in the image. The snapshot files will get mounted over top of
> the image's configuration files upon boot up. This way, you can update
> all of your diskless clients at one time.
...but what if rpm needs to update some of the files which are included
in the snapshot? It won't know and will update the files in nfsroot,
which are not used as the snapshot files are mapped over them when the
real system boots.
> Now, that's the way it is supposed to work. I haven't gotten to the
> point where the snapshot is getting mounted on top of the existing files
> (that's via pivot_root or something, if I remember correctly).
Its not really explained well... 'pivot_root' just swaps root - / - with
another directory. disklessrc starts off with / being the ramdisk,
mounts the nfsroot at /mnt, then the pivot_root command moves the
ramdisk to /.oldroot and the nfsroot to /.
The 'mount snapshot files on top of existing files' is done by 'mount
--bind'. The whole snapshot dir is mounted in /.snapshot then each entry
in the files and files.custom lists is 'mount --bind'ed from the
.snapshot dir over the 'real' location under /.
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