On Wed, Feb 02, 2005 at 12:38:03PM +0100, Christian Andreetta wrote:
> Just a little info: a promising port of unionfs was released for linux,
> with additional features, on
> http://www.fsl.cs.sunysb.edu/project-unionfs.html
>
> This is a kernel module based on lufs (already packaged for Gentoo):
> loading this module, is is possible to have a read-only chroot template
> installation, to be overriden only in the needed _files_ (not only dirs).
sounds good, I don't want to spoil this .. but there
are a few aspects to look at ...
- filesystem benchmarks normal vs. overlay
(probably overlay is a lot slower)
- filesystem cache benchmarking
(probably the overlay uses twice as much cache)
- consistency and migration
(what if vs1 holds a reference to file xy and
you want to update it in the template?)
so IMHO all this stuff needs a lot of testing, which
I would appreciate btw ;)
best,
Herbert
> My installation:
>
> ++ /vservers-template: the chroot with the distro (I use Gentoo for both
> host and guests)
> ++ /vservers/DETAIL/[vserver_id]: the differences from the base
> /vservers-template
> ++ a simple 'mount -t unionfs -o
> dirs=/vservers/DETAIL/[vserver_id]/=rw:/vservers-template/=ro,copyup=preserve
> none /vservers/[vserver_id]/'
>
> Note that the precedence on underlying component {file systems,dirs} is
> left-based (left is priviledged).
> I know I could be more concise on this, but I'm listing nearly all files to
> show they are _really_ few, and, most important, _automatically_ created by
> unionfs (yes, even dirs trees): a simple 'find
> /vservers/DETAIL/[vserver_id]' gives (for a production DB vserver):
> ====================================================================
> /vservers/DETAIL/[vserver_id]/
> /vservers/DETAIL/[vserver_id]/dev
> /vservers/DETAIL/[vserver_id]/dev/log
> /vservers/DETAIL/[vserver_id]/etc
> /vservers/DETAIL/[vserver_id]/etc/mtab
> /vservers/DETAIL/[vserver_id]/etc/mysql
> /vservers/DETAIL/[vserver_id]/etc/syslog-ng
> /vservers/DETAIL/[vserver_id]/etc/syslog-ng/syslog-ng.conf
> /vservers/DETAIL/[vserver_id]/etc/conf.d
> /vservers/DETAIL/[vserver_id]/etc/conf.d/postgresql
> /vservers/DETAIL/[vserver_id]/etc/runlevels/default
> /vservers/DETAIL/[vserver_id]/etc/runlevels/default/mysql
> /vservers/DETAIL/[vserver_id]/etc/runlevels/default/postgresql
> /vservers/DETAIL/[vserver_id]/sys
> /vservers/DETAIL/[vserver_id]/var
> /vservers/DETAIL/[vserver_id]/var/lib
> /vservers/DETAIL/[vserver_id]/var/lib/init.d
> /vservers/DETAIL/[vserver_id]/var/log
> /vservers/DETAIL/[vserver_id]/var/log/wtmp
> /vservers/DETAIL/[vserver_id]/var/log/messages
> /vservers/DETAIL/[vserver_id]/var/log/mysql
> /vservers/DETAIL/[vserver_id]/var/log/mysql/mysql.err
> /vservers/DETAIL/[vserver_id]/var/log/lastlog
> /vservers/DETAIL/[vserver_id]/var/run
> /vservers/DETAIL/[vserver_id]/var/run/utmp
> /vservers/DETAIL/[vserver_id]/var/run/mysqld
> /vservers/DETAIL/[vserver_id]/var/run/mysqld/mysqld.pid
> /vservers/DETAIL/[vserver_id]/var/run/mysqld/mysqld.sock
> /vservers/DETAIL/[vserver_id]/var/run/sshd.pid
> /vservers/DETAIL/[vserver_id]/var/run/random-seed
> /vservers/DETAIL/[vserver_id]/var/run/syslog-ng.pid
> /vservers/DETAIL/[vserver_id]/var/run/cron.pid
> /vservers/DETAIL/[vserver_id]/proc
> /vservers/DETAIL/[vserver_id]/root
> /vservers/DETAIL/[vserver_id]/root/.viminfo
> /vservers/DETAIL/[vserver_id]/root/.psql_history
> /vservers/DETAIL/[vserver_id]/root/.bash_history
> =====================================================================
>
> HTH,
> Christian
>
> PS: I didn't inpected the reason in very deep detail, but inserting the
> 'mount -t unionfs ...' instruction in
> /etc/vservers/[verver_id]/scripts/prepre-start resulted in an empty mount
> point, so I had to do it on host startup...
probably a side effect of the namespace-thingy ...
you might look at the various fstabs ...
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