Date: 7 May 2000 16:39:16 +0200 From: naddy@mips.inka.de (Christian Weisgerber) To: freebsd-current@freebsd.org Subject: Re: Undocumented tape devices in pax(1) Message-ID: <8f3v6k$fnk$1@bigeye.rhein-neckar.de> References: <Pine.BSF.4.21.0005070244160.71785-100000@freefall.freebsd.org>
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Kris Kennaway <kris@FreeBSD.ORG> wrote:
> Can someone explain to me why pax(1) has (undocumented) switches which
> select some tape devices, but apparently randomly numbered ones:
Note that these switches appear only in pax' tar compatibility
personality, which isn't used in FreeBSD. And the reason they're
there is because old versions of tar had them.
I'm looking at 4.3BSD's usr/src/bin/tar.c right now, and it supports
-[014578] to select the respective "/dev/rmt#" device.
> These are selectable through -0, -1, -4, etc. Nevermind the fact that they
> point to devices which have never existed in FreeBSD, but why on earth
> wouldn't you want -2, -3, or -6?
Historical reasons.
Back in 4.3BSD, bits 0 and 1 of the minor number seem to have
specified the device, bit 2 marked non-rewinding, bit 3 6250bpi
(high density?). That explains rmt[0145] well enough, although
rmt[78] remain unclear.
> Anyway, does anyone see the point in leaving these in (changing the
> devices to /dev/rsa<#> and documenting their existence), or should I rip
> them out?
OpenBSD only changed "rmt" to "rst" ("rsa" for us), which isn't
particularly useful. Solaris uses 0..7 to select an entry from
/etc/default/tar, which specifies device name, block size, and tape
size.
I guess mapping -[01] to rsa[01], and -[45] to nrsa[01] still makes
about the most sense.
Unless you intend to revive pax' tar personality under FreeBSD
(which would suggest merging in OpenBSD's changes), I'd say just
leave it.
--
Christian "naddy" Weisgerber naddy@mips.inka.de
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