Re: Chrooting an emulated binary?

[Chuck Yerkes <chuck+obsd@2003.snew.com>]

Put a shell in the chroot area.  Put some utils
(ktrace/truss, etc).  These are TEMPORARY.

Now chroot into it with the shell.
chroot PATH /bin/sh

now try to start your program.

When/if you get it working, REMOVE the shell and utils you
no longer need.

It's just easier to debug interactively.


Quoting C. Bensend (benny@bennyvision.com):
> Hey folks,
> 
> 	I have set up linux emulation on 3.3-STABLE as of May 23rd.  It
> works perfectly - my Neverwinter Nights server comes up just fine.  Yes,
> I'm an addict.  :)
> 
> 	However, since this machine is going out into the untamed wilderness
> eventually, I'd like to be able to chroot the server.  I don't run it
> unattended (only when we fire up a gaming night), and I know that since there
> are shells in /usr/local/emul/redhat the point is mostly moot.  I'm aware
> that there isn't a lot of benefit.  It's become more of a "I wonder if I can"
> sort of thing.
> 
> 	So, using chrootuid from the ports tree, I try to fire it up:
> 
> chrootuid /usr/local/emul/redhat nwn /home/nwn/start-nwn
> Segmentation fault
> 
> 	'start-nwn' is just a simple sh script that sets all my options
> before firing up the server.  OK, so I get a segfault.  Taking a look at
> the ktrace (only the last few lines shown, full dump on request):
> 
>   3777 chrootuid NAMI  "/home/nwn/start-nwn"
>   3777 chrootuid NAMI  "/bin/sh"
>   3777 chrootuid NAMI  "/emul/svr4/lib/ld-linux.so.2"
>   3777 chrootuid NAMI  "/emul/linux/lib/ld-linux.so.2"
>   3777 bash     NAMI  "/lib/ld-linux.so.2"
>   3777 bash     EMUL  "native"
>   3777 bash     RET   execve 0
>   3777 bash     CALL  getuid
>   3777 bash     RET   getuid 1009/0x3f1
>   3777 bash     CALL  getgid
>   3777 bash     RET   getgid 1009/0x3f1
>   3777 bash     CALL  getlogin(0x480a28cc,0xcfbfd414)
>   3777 bash     RET   getlogin 0
>   3777 bash     CALL  setlogin(0x480a28cc)
>   3777 bash     RET   setlogin -1 errno 1 Operation not permitted
>   3777 bash     CALL  ktrace(0xcfbfd1e4,0x4809b7f0,0,0x480a28cc)
>   3777 bash     RET   ktrace -1 errno 2 No such file or directory
>   3777 bash     PSIG  SIGSEGV SIG_DFL code 1 addr=0x0 trapno=1
>   3777 bash     PSIG  SIGSEGV SIG_DFL code 0 addr=0x0 trapno=0
>   3777 bash     NAMI  "bash.core"
> 
> 	Could someone a little more familiar with chroot processes and/or
> linux emulation interpret the last dozen or so lines?  I understand that
> it's bash that's dying (the user nwn's shell), but I'm not really sure
> why.  Limitation of the bash in the linux stuff, perhaps?
> 
> 	Running the start-nwn script as user nwn non-chrooted works fine.
> 
> Thanks for any tips/tricks/cluebats,
> 
> Benny
> 
> 
> -- 
> 
> God is dead and I don't feel all too well either.... -- Ralph Moonen