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From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: [PATCH] dmd: Allow storing early logs before writing to disk
Date: Thu, 11 Sep 2014 16:31:36 +0200
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In-Reply-To: <87d2b36nak.fsf@gmail.com> (David Michael's message of "Wed, 10
	Sep 2014 19:58:11 -0400")
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To: David Michael <fedora.dm0@gmail.com>
Cc: guix-devel@gnu.org

David Michael <fedora.dm0@gmail.com> skribis:

> When using dmd to bring up a read-only file system, it will quit when it
> fails to open a log file for writing.

Out of curiosity, are you trying to use dmd in the initrd, or maybe on
GNU/Hurd?

> This is a proof-of-concept patch that adds the option to start writing
> logs to a string port.  It allows having a dmdconf.scm that runs fsck,
> makes the disk writable, and then starts writing past and future log
> messages to disk with (start-logging "/var/log/dmd.log").

That sounds useful.

> Does anyone have any thoughts on this?  Is there a better way to handle
> this case?

The problem is: when does it figure out that it can now write to the
file?

The ideal thing would be:

  1. Run =E2=80=98dmd -l foo.log=E2=80=99.
  2. If foo.log is not writable, then make =E2=80=98log-output-port=E2=80=
=99 a string
     port.
  3. When foo.log becomes writable, have =E2=80=98log-output-port=E2=80=99 =
point to it
     and dump previously buffered data.

But #3 is difficult.

Maybe instead of using a string port, we could use a string port that
keeps trying to open the log file?

It would be best to use inotify (or the Hurd=E2=80=99s fs_notify), of cours=
e.

Ludo=E2=80=99.