From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
To: buildroot@busybox.net
Subject: [Buildroot] [RFC 3/6] system: add mdev-only /dev management (without devtmpfs)
Date: Wed, 9 Sep 2015 15:54:27 +0200 [thread overview]
Message-ID: <20150909155427.53f9c8b5@free-electrons.com> (raw)
In-Reply-To: <55F02630.5050500@lucaceresoli.net>
Dear Luca Ceresoli,
On Wed, 9 Sep 2015 14:29:36 +0200, Luca Ceresoli wrote:
> The first problem is we'd have an empty /dev since the mount until the
> execution of S10mdev. This prevents busybox init from executing all
> lines in inittab after the mount, since they would try to open
> /dev/null. Symptom: "can't open /dev/null: No such file or directory".
> The fix should be simply:
>
> -null::sysinit:/bin/mkdir -p /dev/pts
> -null::sysinit:/bin/mkdir -p /dev/shm
> -null::sysinit:/bin/mount -a
> -null::sysinit:/bin/hostname -F /etc/hostname
> +::sysinit:/bin/mkdir -p /dev/pts
> +::sysinit:/bin/mkdir -p /dev/shm
> +::sysinit:/bin/mount -a
> +::sysinit:/bin/hostname -F /etc/hostname
>
> Lines up to the /dev mount might be changed as well to have a more
> uniform style, but it's not strictly needed.
It actually looks better to me to *not* redirect the output of those
commands to /dev/null. I don't know why we are doing this, but it means
that if any of those commands wants to display something, it is
redirected to oblivion. Not good. So it looks better to continue using
the stdout/stderr set up by the kernel for the init process.
BTW, does this means that in the minimal static device table, we only
need /dev/console? That's the only device that is opened by the kernel
directly, I believe /dev/null was only needed for those lines.
> But ehen, if any user has an S05something that uses /dev, it would
> break. In order to reduce the risk to nearly zero, we might move
> S10mdev to S00mdev, so it runs (most likely) as the first script.
>
> This would slightly change the current behaviour for all cases, and
> start S01logging after mdev, not before. I tested it quickly and it
> looks like it works. Can you think of any problem with moving S10mdev
> to S00mdev?
In principle, it seems better to me if the devices are all set up
before starting anything else, so if it works, I'm all for S00mdev. The
only question is whether mdev logs things to syslog, and if so what
happens to those messages that are emitted before syslog is started.
Thanks!
Thomas
--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
next prev parent reply other threads:[~2015-09-09 13:54 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-08 21:28 [Buildroot] [RFC 0/6] mdev-only /dev management (without devtmpfs) Luca Ceresoli
2015-09-08 21:28 ` [Buildroot] [RFC 1/6] Move mounting /sys from fstab to inittab Luca Ceresoli
2015-09-09 9:12 ` Arnout Vandecappelle
2015-09-08 21:28 ` [Buildroot] [RFC 2/6] system: clarify /dev management using devtmpfs + {mdev, eudev} Luca Ceresoli
2015-09-09 9:40 ` Arnout Vandecappelle
2015-09-09 10:53 ` Luca Ceresoli
2015-09-09 10:54 ` Arnout Vandecappelle
2015-09-08 21:28 ` [Buildroot] [RFC 3/6] system: add mdev-only /dev management (without devtmpfs) Luca Ceresoli
2015-09-09 9:21 ` Arnout Vandecappelle
2015-09-09 12:29 ` Luca Ceresoli
2015-09-09 12:32 ` Arnout Vandecappelle
2015-09-09 13:54 ` Thomas Petazzoni [this message]
2015-09-14 13:47 ` Luca Ceresoli
2015-09-14 22:23 ` Arnout Vandecappelle
2015-09-15 22:35 ` Luca Ceresoli
2015-09-14 20:53 ` Peter Korsgaard
2015-09-14 21:34 ` Thomas Petazzoni
2015-09-14 21:38 ` Peter Korsgaard
2015-09-15 7:30 ` Thomas Petazzoni
2015-09-15 8:09 ` Peter Korsgaard
2015-09-15 9:41 ` Thomas Petazzoni
2015-09-15 12:01 ` Peter Korsgaard
2015-09-15 12:27 ` Arnout Vandecappelle
2015-09-15 12:32 ` Peter Korsgaard
2015-09-18 16:37 ` Luca Ceresoli
2015-09-15 13:03 ` Thomas Petazzoni
2015-09-15 13:14 ` Peter Korsgaard
2015-09-15 22:34 ` Luca Ceresoli
2015-10-01 9:36 ` Luca Ceresoli
2015-10-01 10:03 ` Peter Korsgaard
2015-09-15 22:31 ` Luca Ceresoli
2015-09-16 7:32 ` Peter Korsgaard
2015-09-18 15:47 ` Luca Ceresoli
2015-09-09 9:34 ` Arnout Vandecappelle
2015-09-09 11:23 ` Thomas Petazzoni
2015-09-09 11:29 ` Thomas Petazzoni
2015-09-09 20:33 ` Arnout Vandecappelle
2015-09-14 16:07 ` Luca Ceresoli
2015-09-14 16:05 ` Luca Ceresoli
2015-09-14 19:34 ` Thomas Petazzoni
2015-09-14 20:19 ` Arnout Vandecappelle
2015-09-15 22:07 ` Luca Ceresoli
2015-09-08 21:28 ` [Buildroot] [RFC 4/6] system: strip the initial /dev for mdev-only /dev management Luca Ceresoli
2015-09-08 21:28 ` [Buildroot] [RFC 5/6] docs/manual: document "Dynamic using mdev only" " Luca Ceresoli
2015-09-09 10:39 ` Arnout Vandecappelle
2015-09-08 21:28 ` [Buildroot] [RFC 6/6] **** DO NOT COMMIT THIS **** ugly stuff to test mdev-only " Luca Ceresoli
2015-09-09 9:26 ` [Buildroot] [RFC 0/6] mdev-only /dev management (without devtmpfs) Arnout Vandecappelle
2015-09-09 11:30 ` Thomas Petazzoni
2015-09-14 21:03 ` Peter Korsgaard
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