Virtualization on FreeBSD

Paul Pathiakis pathiaki2 at
Thu Jul 30 13:19:10 UTC 2015

On 07/30/2015 08:55, Terje Elde wrote:
> On 30. juli 2015, at 14:29, "William A. Mahaffey III" <wam at> wrote:
>> Can jails run non-native guests/VM's (M$FT, for example) ? I thought I saw something about this online a while back, but haven't been able to re-acquire it .... I'm on 9.3R-p20, BTW ....
> Jails are not - and this is the good part - virtualization. It's a way of compartmentalizing so you can have multiple FreeBSD installs in different jails, or even just single programs.
> For web for example, I'll often run webservers in one jail, and database server in another, to get a degree of isolation between them.
> It's not really intended to solve running another operating system, though you might be able to run some linux binaries in a jail.
> Terje
I agree with the first part.  They are not virtualization... they don't 
hog resources that they don't need (like CPUs, disk space, etc - They're 
to resource sharing like zpools are to ZFS - everything is in one bucket 
that everyone shares;  Before ZFS, in order to keep logging from wedging 
a system, you'd have to create a partition of certain sizes (of course, 
prior to the ability to grow filesystems).)

Someone mentioned they are enhanced 'chroot'.  Well, chroot has been 
proven insecure in many regards over time.  Jails have been found to be 

I disagree with the last part.  I implemented debootstrap and loaded 
Debian 6 when I needed a Linux specific app.  *shrug*  No big deal.

Same thing for CentOS.

I expect BHYVE will be the virtualization for FreeBSD in the future.

Also, jails are being enhanced to have virtualization "features". That 
is, there looks to be work going on to allow the complete 
allocation/dedication of resources to a jail.  I'm not sure this should 
happen, especially CPU/RAM.  Of course, if it could be made such that I 
have a 16 core CPU and have 32 jails....  I might want to be able to 
allow a load of 2.00 in one jail so allow the other 31 to share the 
remaining CPUs.  Abilities on those lines would keep jails from becoming 
the issue that virtualization has... dedicating resources that can't be 
used by other virtual machines.  I like the fact I don't need to have at 
least as many cores as machines in virtualization.

(Of course, they may have resolved this and my knowledge is out of date)


More information about the freebsd-questions mailing list