[systemd-devel] EXT :Re: Disk Label Handling

[Boyce, Kevin P [US] (AS)]

Lennart,

Thanks for the reply.  I am looking at the man page now.  Am I correct that if two filesystems are detected by udev sequentially that the last one updates the /dev/disk/by-label symlink, and the reference that the first one lost out?  Is there any way to preserve that the first filesystem detected keeps the link and doesn't get overwritten by subsequent events?

The link_priority option to me does not seem to have a method where all devices with duplicated filesystem labels have a unique symlink.  More importantly, this approach would only work if custom device specific rules are added, not for the generic rule "ENV{ID_FS_USAGE}=="filesystem|other|crypto", ENV{ID_FS_LABEL_ENC}=="?*", SYMLINK+="disk/by-label/$env{ID_FS_LABEL_ENC}"" as in the 60-persistent-storage.rules file.

Kevin

-----Original Message-----
From: Lennart Poettering <lennart at poettering.net> 
Sent: Friday, July 26, 2019 9:24 AM
To: Boyce, Kevin P [US] (AS) <Kevin.Boyce at ngc.com>
Cc: systemd-devel at lists.freedesktop.org
Subject: EXT :Re: [systemd-devel] Disk Label Handling

On Fr, 26.07.19 13:18, Boyce, Kevin P [US] (AS) (Kevin.Boyce at ngc.com) wrote:

> Good morning list!
>
> How is udev supposed to handle the creation of /dev/disk/by-label/ 
> symlinks when there are more than one filesystems detected with the 
> same label, such as DATA.
>
> In the past I remember udev linking these subsequently detected 
> filesystems as DATA_1, DATA_2, etc.  Yet with systemd's udev 
> implementation I do not observe that to be the case.  Is there some 
> sort of setting to change or rule to modify to get that behavior?
> Or is that now a more complicated problem than it used to be?

one wins. you can tweak which with link_priority in OPTIONS. See udev(7).

udev keeps a list, and thus if you unplug a device the symlink is likely updated to point to a different devices, until you remove all.

Lennart

--
Lennart Poettering, Berlin