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Message-ID: <20250828202101.GA18768@openwall.com>
Date: Thu, 28 Aug 2025 22:21:01 +0200
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: suppressing potfile / minimizing writes?
Hi Royce,
On Tue, Aug 26, 2025 at 09:22:07PM -0800, Royce Williams wrote:
> I would like to do the equivalent of disabling potfile writing entirely, or
> write it to /dev/null. This is for various benchmarking tasks, in which I
> do not want I/O write speed to affect the results.
>
> I tried --pot=/dev/null, but john attempts to chmod the potfile prior to
> running, which fails on Linux so john aborts. I then tried a FIFO to do the
> equivalent, which john explicitly disallows.
>
> How can I accomplish this?
We do not have a feature like this, sorry. Maybe you'd contribute it.
If you have lots of RAM, you can place (at least) the pot file on tmpfs,
e.g. under /dev/shm or on a separate tmpfs mount. And "swapoff -a".
Alternatively, I thought you could create and use a /dev/null equivalent
device file that would have the user as owner - but upon testing this, I
see it fails on our fsync() call, unfortunately.
Alexander
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