[nycbug-talk] nullfs, jails and quotas

[Okan Demirmen]

On Thu 2006.01.12 at 14:09 -0500, Isaac Levy wrote:
> Hey Charles,  All,
> 
> Not a very timely response, but I feel I should weigh in on this issue.
> 
> On Jan 9, 2006, at 7:17 PM, Charles Sprickman wrote:
> 
> >Here's a quick tip:
> >
> >Don't try using nullfs to mount /usr/ports (or anything else) into  
> >a jail and then enable quotas on the jail's partition.  Really bad  
> >juju there.
> >
> >This is on 6-stable.  On running quotacheck after killing off all  
> >jails, that process was hung, and anything else that touched that  
> >partition went into a "disk wait" state that was unkillable.   
> >Running a shutdown just left the machine hanging in a not-quite- 
> >dead state.  It seems like the kernel will block forever on any  
> >processes waiting for that partition.  A reboot alone did not clear  
> >it, the background fsck also hung.
> >
> >Just a friendly warning for anyone doing that kind of tinkering  
> >remotely - always unmount your nullfs mounts before screwing with  
> >quotas...
> 
> Nullfs is outright unsuported, as I've said during the course of  
> several lectures on jail(8).  The man page for mount_nullfs(8) states:
> 
> <snip>
> BUGS
>      THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT  
> DOESN'T WORK)
>      AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM.  USE AT  
> YOUR OWN
>      RISK.  BEWARE OF DOG.  SLIPPERY WHEN WET.
> 
>      This code also needs an owner in order to be less dangerous -  
> serious
>      hackers can apply by sending mail to <hackers at FreeBSD.org> and  
> announcing
>      their intent to take it over.
> <snip>
> 
> Charles: I'm dreadfully empathetic if this cost you time and energy.

and as ray _almost_ eluded to a bit earlier, there's a reason why the
layered filesystems were pulled from at least openbsd.