From: Christian Andreetta (satya_at_gentoo.org)
Date: Wed 02 Feb 2005 - 11:38:03 GMT
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).
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...
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