Subject: bug#74847: change default tar format from v7 to ustar (was: Re: reproducible tar archives)

From: Simon Josefsson <[email-masked]>
Date: Fri, 13 Dec 2024 12:29:27 +0100

Hi automake folks,

What do you think about changing Automake's default tar format from v7
to ustar?

Are you aware of any system 'tar' that does doesn't cope with ustar?

What do you think about defaulting to the --format=posix PAX format?  It
may be just as safe as ustar, and only if a package uses some feature
(like >255 long filenames) that require PAX then it would be enabled,
otherwise it will remain ustar-compatible.

Discussion on the gnulib list suggests that at least ustar ought to be
safe to use these days.

/Simon

Bruno Haible via Gnulib discussion list <[email-masked]> writes:

> Simon Josefsson wrote:
>> Possibly automake can move
>> from v7 to ustar.  Adding this to gnulib now allows us to gain
>> experience with it.
>
> I have already experience with it: Since 2018, all tarballs of GNU gettext
> were made with --format=ustar. I have tested them on all possible platforms,
> from HP-UX 11 to IRIX 6.5, from AIX 7 to NetBSD, and not encountered a
> problem — nor received a complaint or bug report because of it.
>
> So, from my point of view, we can ask the Automake team to adopt
> --format=ustar now.