Re: [PATCH] change default --format from gnu to posix

[Mike Frysinger]

On 13 Dec 2021 12:30, Sergey Poznyakoff wrote:
> Regarding reproducible build concerns, expressed by Paul: I don't
> believe it is an issue.  Reproducible tarballs in PAX format are
> easily made with the following option:
> 
>   --pax-option=exthdr.name=%d/PaxHeaders/%f,atime:=0,ctime:=0
> 
> (btw, it is mentioned in the tar docs as well).

there's also the matter of uid/gid, albeit to a lesser degree.  GNU ar has
a "deterministic mode" to throw all of these issues into one easy flag for
users.  maybe GNU tar should grow a similar option ?  i think it's pretty
error prone to expect people to know the full command line they have to use
in order to get something basic like reproducible archives.  especially if
it changes by format.

atm, i think the full command line is:
LC_COLLATE=C tar \
  --format=pax \
  --sort=name \
  --owner=0 --group=0 \
  --pax-option=exthdr.name=%d/PaxHeaders/%f,atime:=0,ctime:=0 \
  -cf foo.tar foo/

use of --mtime=0 is prob debatable.
-mike

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