Re: [PATCH] mdadm: autodetect being run in an initramfs

On 27 September 2012 23:11, Dave Reisner [off-list ref] wrote:

On Sep 27, 2012 6:08 PM, "Dmitrijs Ledkovs" [off-list ref]
wrote:

quoted

On 27 September 2012 15:41, Dave Reisner [off-list ref] wrote:

quoted

Key off of the existance of /etc/initrd-release as an indicator that
mdadm is running in early userspace and set the __offroot flag. This
allows the same udev-based assembly rules to be valid both off and on
root and, moreover, will propagate to mdmon, should it need to be
started.

And what shall non-systemd systems do?

Add the file, of course!

quoted

I don't have /etc/initrd-release in my initramfs-tools generated
initrd, and so far didn't have a usecase for it.
Should it be an empty file?

Yep, just an empty file. It only serves to be a marker since there really
isn't any other heuristic for detecting early userspace.

This is a bit backwards. As far as I understand the systemd & udev
merge now means that udev rules cannot spawn long running processes
and instead should have a proper systemd units instead. And since
systemd is running all of the initramfs surely it can set up an
environment without adding pointless files, e.g. an environment
variable?

Please correct me, if I am wrong, cause I really don't understand
either this patch or systemd or both.

quoted

quoted

Signed-off-by: Dave Reisner <redacted>
---
 mdadm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mdadm.c b/mdadm.c
index 4c7c5ea..557e00b 100644
--- a/mdadm.c
+++ b/mdadm.c

@@ -1106,6 +1106,11 @@ int main(int argc, char *argv[])
                exit(0);
        }

+       /* auto-detect being on an initramfs
+        *

http://www.freedesktop.org/wiki/Software/systemd/InitrdInterface */
+       if (access("/etc/initrd-release", F_OK) == 0)
+               __offroot = 1;
+
        if (!mode && devs_found) {
                mode = MISC;
                devmode = 'Q';
--
1.7.12.1

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