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Date: Thu, 4 Jun 2015 00:11:18 +0200
From: Luis Rocha <>
Subject: Re: Multiple GPU and Fork

After following the mentioned tutorial, installing AMD drivers and sdk, JtR
it is running well with a non-priv account and using all GPU's with the
fork option.

$ ./john --format=md5crypt-opencl --dev=0,1 --fork=2
Loaded 1726 password hashes with 1726 different salts (md5crypt-opencl,
crypt(3) $1$ [MD5 OpenCL])
Node numbers 1-2 of 2 (fork)
Device 1: Pitcairn [AMD Radeon HD 7800 Series]
Device 0: Hawaii [AMD Radeon R9 200 Series]
Press 'q' or Ctrl-C to abort, almost any other key for status
2 0g 0:00:02:08  3/3 0g/s 738.5p/s 1306Kc/s 1306KC/s GPU:59°C util:97%
fan:56% supro..batas1
1 0g 0:00:02:07  3/3 0g/s 1646p/s 3013Kc/s 3013KC/s GPU:84°C util:100%
fan:64% ceds24..sevoty

Once again thanks for the help .. looks like in this case it was something
on my system.

On Wed, Jun 3, 2015 at 9:00 PM, Luis Rocha <> wrote:

>> ... but you probably didn't have DISPLAY nor XAUTHORITY set to talk to
>> your X server from that root shell.  (Maybe your bad habit of running
>> john as root has finally backfired.)  You should be running john from a
>> user account and environment authorized to talk to your X server.  As a
>> test, try running "xterm &" from the shell that you use to start john -
>> will it start, will it appear on your desktop?  If so, exit the xterm
>> and then start john.  If not, correct this first.
> I did try from a non-priv account "xterm &" and a it appeared on my
> desktop. I started JtR from there but same behavior. I exited and started
> JtR and the same behavior.
> I also have the DISPLAY variable and allowed X access with "xhost +"
> $ cat .bashrc | grep DISPLAY
> export DISPLAY=:0
> $ xhost +
> access control disabled, clients can connect from any host
> Then I logged off and connected back using ssh and executed:
> $ sudo ./john --format=md5crypt-opencl --dev=0,1
> --fork=2
> [sudo] password for user:
> Loaded 1726 password hashes with 1726 different salts (md5crypt-opencl,
> crypt(3) $1$ [MD5 OpenCL])
> Node numbers 1-2 of 2 (fork)
> Device id 0 not working correctly, skipping.
> Device id 1 not working correctly, skipping.
> No OpenCL devices found
> Device 0: Hawaii [AMD Radeon R9 200 Series]
> Calculating best global worksize (GWS); max. 500ms single kernel
> invocation.
> Raw speed figures including buffer transfers:
> Had to run  JtR with sudo because without sudo the opencl devices were not
> listed .. maybe I have somehow a broken installation of drivers and so on
> and so forth ...
> I am going to reinstall the OS and follow this guide
> .. then if you
> someone is willing to help me debug this FORK issue I am all for it.
> On a different note, I got a Gygabyte R9 290x in case someone wants to
> perform some tests I am available to run those.
> Thank you for the help!
> Luis

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