[arch-projects] [devtools] [PATCH 5/9] arch-nspawn: Avoid errors where $working_dir is longer than HOST_NAME_MAX.

Luke Shumaker lukeshu at sbcglobal.net
Sun May 11 00:04:31 EDT 2014

At Sat, 10 May 2014 22:36:44 -0400,
Dave Reisner wrote:
> On Sat, May 10, 2014 at 10:22:07PM -0400, Luke Shumaker wrote:
> > +#HOST_NAME_MAX="$(printf '%s\n' '#include <limits.h>' 'HOST_NAME_MAX'|cpp -|sed -n '$p')"
> No need to write the include as if this were a source file, just tell
> cpp about it directly:
>   cpp -I limits.h <<<HOST_NAME_MAX | ...

That doesn't work, but this does:

  cpp -include limits.h <<<HOST_NAME_MAX | ...

I'd never had occasion to use that flag before, so thank you!

> > +if [[ ${#machine_name} -gt "$HOST_NAME_MAX" ]]; then
> > +	machine_name="${machine_name:(-${HOST_NAME_MAX})}"
> > +	machine_name="${machine_name#-}"
> I think this is worth warning about, since it might result in name
> clashes.

Is it any more likely to cause clashes than the existing machine name
munging?  64 characters is a lot, and I figure that the end is the
part that is most likely to change.

What about passing '-q' to systemd-nspawn and not directing its stderr
to /dev/null?  That way the user gets a reasonably friendly "Failed to
register machine: Machine '$machine_name' already exits", as well as
a message for any other errors that may occur.  IIRC, the reason
stderr was directed to /dev/null was that at the time it was written,
systemd-nspawn didn't have a '-q' flag.

Happy hacking,
~ Luke Shumaker

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