DNS+chroot (Linux): no libraries needed in chroot cell !?!

Barrett Richardson barrett at phoenix.aye.net
Mon Aug 16 15:24:55 UTC 1999



On 12 Aug 1999, Dr. Dorothea Muecke-Herzberg wrote:

> Hi there,
> 
> has anyone tried to run named chrooted and can help me with my
> problems? (running Linux-2.2.6 on a Compaq Proliant1600 and
> bind-8.2.1)
> 
> First:
> I did build named according to INSTALL. (No problems there,
> except if I want to build a statically linked version, but that's
> another story)
> 
> For testing purposes I built a chroot environment without any
> libraries
> to see which ones are needed and started holelogd (for binding
> /jail/dns/root/dev/log to syslogd) and named:
>    named -u named -g named -t /jail/dns/root
> 
> To my utter surprise named started without any complaint !?! 
> Here you see the excerpt of /var/log/messages:
> 
>  Jul 21 12:40:42 bastion named[2770]: starting.  named 8.2.1 
>  Jul 20 14:50:08 GMT 1999 ^Iroot at bastion:/jail/src/dns/src/bin/named
>  Jul 21 12:40:42 bastion named[2770]: hint zone "" (IN) loaded
> (serial0)
>    .
>    .
>  Jul 21 12:40:42 bastion named[2770]: listening on [127.0.0.1].53 (lo)
>  Jul 21 12:40:42 bastion named[2770]: Forwarding source address is
>    [0.0.0.0].53
>  Jul 21 12:40:42 bastion named[2771]: chrooted to /jail/dns/root
>  Jul 21 12:40:42 bastion named[2771]: group = named
>  Jul 21 12:40:42 bastion named[2771]: user = named
>  Jul 21 12:40:42 bastion named[2771]: Ready to answer queries.
> 
> First question: What is going on here? Why doesn't named need the
> shared libraries?
>

References to the shared libs were established before the chroot
occurred.

> _______________________
> 
> Second:
> My second problem appears 45 min later. See /var/log/messages:
> 
>  Jul 21 13:28:02 bastion named[2937]: can't exec /usr/sbin/named-xfer:
>  No such file or directory
> 
> But there is an named-xfer in /jail/dns/root/usr/sbin (in /usr/sbin
> too!)!

Here is where the shared libs come in. I know the "No such file
for directory" message is a bit vague -- it may be more informative
if you throw libc.so into /jail/dns/root/usr/lib -- may even
spit out a message like "named-xfer: could not load shared library
libxx.so".

> According to the above logfile the chroot to /jail/dns/root worked
> fine.
> 
> Second question: Has someone experienced the same? Can someone tell me
> what's wrong?
> ________________________
> 
> Any help will be appreciated. Thanks in advance       
> 
> Dorothea
> 
> 
> 



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