I'm not sure about union fs, never had a real use for it yet.... I have a similair setup as you. I have about 4 jails running so far (~8 more to go). I've written a fairly large bash scipt to build the jails + configure them automagically too. I've got a 120GB drive in that system, so for me I don't really have a problem with space. What I use nullfs for is sharing data between jails, for example:
/secure/files/mail <- mail spools would be shared using: (/etc/crontab entries) none /secure/files/mail /secure/internal/smtp/postfix/server/var/spool/mail rw,noexec,nosuid,nodev 0 0 none /secure/files/mail /secure/internal/imap/courier/server/var/spool/mail rw,noexec,nosuid,nodev 0 0 haven't really got these up and running yet (ie. I don't really know if postfix + courier both work inside a jail). ATM I'm stuck on my file server jail, which may never work. I do have djbdns cache+server running. Anyway, nullfs is great for "remounting" parts of the file system. I would not use that to remount parts of the file system that have executables on them in rw mode, only ro. You could mount the base / fs using nullfs onto the jail / filesystem but this would be tricky because you would have to deal with things like syslogd base + syslogd(s) jail both writing to /var/log/. You could mount each directory using nullfs (/bin /sbin, etc) onto the jails and I think this would work. I would note the warnings in the man pages about this stuff being experimental tho. You could save space by using the same executables and libs while having seperate /var/ /etc/ etc dirs in the jail but it would be a bit of work to figure out what dirs to mount_nullfs and what dirs to have as real dirs. Oh, btw, I know about as much about fs's as you do too, so your milage may vary... -Kenny On August 3, 2003 04:09 pm, Lewis Thompson wrote: > Hi, > > I currently have a bunch of jails running on my FreeBSD box. I've > done this by making installworld a number of times, each time with a > different DESTDIR (say /jail1, /jail2, /jail3). Clearly this is using a > significant amount of space on the machine. > > I've been reading about unionfs and nullfs (well, more skim reading > really; I'm not FS guru, which is why I'm asking here) and one of these > sounds like it could be the idea solution. At first glance I'd say that > unionfs would be the way to go. > > My question about unionfs: if I use this as a base dir for all of my > jails and decide to ``upgrade'' the base system will it actually work? > I mean, when I start installing stuff through the ports does it ever > modify the base system in any way? If it does, then surely a base > system upgrade will appear to leave the old ports-created files (because > the upper layer changes override the lower unionfs fs). > > Secondly, I don't really understand nullfs. Would this be a > ``better'' solution than using unionfs? Maybe it isn't even a solution, > but if it is, a pointer to some useful articles would be great (aside > man mount_nullfs; I've read that but don't fully understand). > > Thanks very much! > > -lewiz.