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Bug#984650: update-initramfs fails when /etc/systemd/network/99-default.link is symlink to /dev/null



Hi Cyril,

Thank you for the quick reply

As Ben also pointed out, I probably have indeed mixed up /dev/zero and /dev/null and had already fixed that by using an empty file. Nevertheless the result was pretty odd (the disk filling up rapidly) and very confusing so might still be useful to prevent this (if possible).

Why not use a cp -aLt <directory> {} instead to prevent this?

regards,

Frederik


> On 6 Mar 2021, at 16:27, Cyril Brulebois <kibi@debian.org> wrote:
> 
> Hello Frederik,
> 
> It seems there's some confusion around special character devices. Your
> subject mentions /dev/null…
> 
> Frederik Lindenaar <debian@frederik.lindenaar.nl> (2021-03-06):
>> When one disables the "Predicatble Network InterfaceNames" 
>> by making /lib/systemd/network/99-default.link a symlink to /dev/zero then
> 
> … but this is about /dev/zero (not the same thing! — see `man 4 null`).
> 
>> update-initramfs will fail as the copy of this symlink will fill-up all space
>> available in /var/tmp and makes it impossible to install any kernel image
>> 
>> the culprit is the following command executed by update-initramfs:
>> 
>> 	find /etc/systemd/network -name *.link -execdir cp -pt /var/tmp/ {} +
>> 
>> As it (and should) dereference de symlink, it reads zero bytes from
>> /dev/null until the disk is full.
> 
> … and here you write /dev/null but what you describe happens with
> /dev/zero instead.
> 
>> Changing the symlink to a zero byte file resolved the issue for me but
>> as this approach is one of the recommended approaches to disable
>> predicatble network interface names (see [1]) others may also bump
>> into this.
>> 
>> [1] https://wiki.debian.org/NetworkInterfaceNames#How_to_get_it_back
> 
> This correctly describes a symlink to /dev/null, and not /dev/zero which
> appears to be what you're trying to use.
> 
> Fix your symlink, and you should be good to go?
> 
> 
> Cheers,
> -- 
> Cyril Brulebois (kibi@debian.org)            <https://debamax.com/>
> D-I release manager -- Release team member -- Freelance Consultant


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