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Date:      Mon, 8 Jul 1996 05:47:38 +1000
From:      Bruce Evans <bde@zeta.org.au>
To:        joerg_wunsch@uriah.heep.sax.de, wpaul@skynet.ctr.columbia.edu
Cc:        current@freebsd.org
Subject:   Re: Which tools can back up inodes with 32bit minor numbers ?
Message-ID:  <199607071947.FAA00113@godzilla.zeta.org.au>

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>> Well, as i wrote, the existing static /dev is about to be killed
>> anytime soon.  MAKEDEV as well -- shouldn't you have it already
>> noticed.

>Wrong.

>The existing /dev and MAKEDEV are _not_ going away any time soon.
>Not on any of the systems I maintain anyway (including my personal 
>machines at home). You'll never catch me putting 'options DEVFS' in
>any of my kernel config files. And the day it changes from optional
>to mandatory is the day I stop running FreeBSD.

Stop now before you become more attached to it :-).  Devfs in some form
is necessary for avoiding a limited fixed mapping of device names to
drivers.

>Getting back to the subject at hand, dump and restore are
>supposed to preserve _everything_, including 32-bit major/minor
>values (we got 'em, we gotta deal with 'em). Ideally, tar and cpio
>should too. If they don't, they should be made to, but only if their 
>archive formats allow it without breaking compatibility with all the 
>other tar and cpio implementations on the planet. If dump and restore 

>Getting back to the subject at hand, dump and restore are
>supposed to preserve _everything_, including 32-bit major/minor
>values (we got 'em, we gotta deal with 'em). Ideally, tar and cpio
>should too. If they don't, they should be made to, but only if their 
>archive formats allow it without breaking compatibility with all the 
>other tar and cpio implementations on the planet. If dump and restore 

They can't.  E.g., tar format has 8-byte null-terminated strings with
octal digits for the major and the minor numbers.  This limits the
number of bits to 21.  Gnu tar has a bug that further limits the number
of bits to 18 (it blank terminates as well as null terminates the
strings).  Gnu cpio has the same bug as gnu tar.  `pax -x ustar' handles
the full 21 bits.  Gnu cpio seems to handle 21 bits minors correctly for
input (it handles tar output from pax).  Gnu tar can't handle tar output
from pax or cpio (sio cpio/README) so I couldn't test it on pax's
output.

Bruce



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