cvs commit: src/usr.sbin/jexec jexec.8 jexec.c

Julian Elischer julian at
Tue May 27 17:20:31 UTC 2008

Alexander Leidinger wrote:
> Quoting Frank Behrens <frank at> (from Mon, 26 May 2008 
> 20:48:23 +0200):
>> The rc.conf jail framework also requires unique hostnames for jails, 
>> because the jail-ids are
>> write to /var/run.
> On a related note: JIDs are not known in advance, so doing some rc.d 
> stuff which associates a specific X with a jail is not easy. So for 
> example the zfs feature to  assign a zfs filesystem to a jail is 
> practiaclly useless at the moment for stuff which shall be available 
> after a reboot without admin intervention (it is not guaranteed that the 
> jails get the same JID again on reboot).
> In I have a 
> patch which also uses the hostname of a jail to allow access to /dev/io 
> in the jail (if the admin of the host made it visible in the jail). If 
> ZFS would use the hostname, it would make it more useful (but maybe we 
> would need some magic in the jail code to notify ZFS about a new jail, I 
> haven't checked how ZFS is working in this regard).
> So basically we need some unique value which is handed out by the admin 
> and doesn't change after a reboot. For me the hostname is a good 
> approximation for this (my hostnames are unique, and I have full control 
> over them).
> Bye,
> Alexander.

using Jail identifiers that are allocated also fits into vimage, 
however vimage is hierarchical..

"."        is the base jail/vimage.
".foo"     is a jail/vimage called foo that was made in "."
"" is a jail/vimage called bar that was made inside ".foo"

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