|
|
|
|
|
|
| Author |
Message |
jpd
*nix forums Guru
Joined: 22 Feb 2005
Posts: 877
|
 Posted: Wed Oct 26, 2005 11:15 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
Begin <1130349771.099051.207690@g43g2000cwa.googlegroups.com>
On 2005-10-26, Maury Markowitz <maury_markowitz@hotmail.com> wrote:
| Quote: | Many moons ago I backed up a lot of personal work on a DLT tarball. I
thought the format would remain common *sigh*.
|
Well, time to find out a) what format that tape is, as not all DLTape
drives can read all DLTapes, and b) what the format of that archive on
the tape is.
| Quote: | I recently came across a PowerMac 8550 that has a drive in it. I assume
it's the same or extremely similar, because the tarball was made on a
Mac G3 (biege).
|
But with what OS driving it? And hence which tar(1) were you using? What
are the exact problems you're having? Did you check the blocking factor?
| Quote: | I'm thinking that the easiest way to try to read this thing would be to
install NetBSD, read the tarball, and then figure out how to get it
back off later.
|
To me it isn't clear at all whether a powermac and a powermac g3 produce
compatible formats. Or rather, since tape archiving isn't a function
of the hardware --apart from the tape drive itself-- and not even of
the OS, it isn't clear whether your unspecified tape archivers on
unspecified OSen produce compatible formats. And whether going out on
a limb and using a wildly different system will help I won't hazard a
guess.
| Quote: | When I look at the supported hardware, I see that the 8550 is
supported. *phew* However I do not see any mention of DLT (or 8mm,
whatever it is). Does anyone know if a SCSI-attached tape is supported?
|
8mm is the width of the tape. Common widths are 4mm (eg DAT), 8mm
(eg exabyte), .5"/12.7mm (QIC, others). DLT uses 12.7mm wide tape.
If a tape has a SCSI interface then it usually is supported. Much like
all SCSI disks are supported whenever any are supported.
Likely as not NetBSD will allow you to read the tape (eg using dd) IFF
you know the right blocking factor, but whether its tar can read the
contents of the archive I can't say.
--
j p d (at) d s b (dot) t u d e l f t (dot) n l . |
|
| Back to top |
|
 |
jpd
*nix forums Guru
Joined: 22 Feb 2005
Posts: 877
|
| Posted: Thu Oct 27, 2005 12:26 am Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
[following up to self]
Begin <3sah05Fne40jU1@individual.net>
On 2005-10-26, jpd <read_the_sig@do.not.spam.it.invalid> wrote:
| Quote: |
8mm is the width of the tape. Common widths are 4mm (eg DAT), 8mm
(eg exabyte), .5"/12.7mm (QIC, others). DLT uses 12.7mm wide tape.
|
Clearly wasn't awake yet. QIC is quarter inch tape, or about 6mm wide.
--
j p d (at) d s b (dot) t u d e l f t (dot) n l . |
|
| Back to top |
|
|
Maury Markowitz
*nix forums beginner
Joined: 26 Oct 2005
Posts: 8
|
| Posted: Thu Oct 27, 2005 12:20 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
jpd wrote:
| Quote: | Well, time to find out a) what format that tape is, as not all DLTape
drives can read all DLTapes, and b) what the format of that archive on
the tape is.
|
The tape (holding it now) is a 4mm DL 90m. I assume the 90m is the
length, and thus unimportant.
The archive was created using Rhapsody, I believe I used whatever the
most simple and basic possible Unix command to put it onto the tape, I
think it's tgz format written out using dd (??).
| Quote: | But with what OS driving it? And hence which tar(1) were you using? What
are the exact problems you're having? Did you check the blocking factor?
|
I do not know what "blocking factor" is, so I assume "the default".
Rhapsody was essentially BSD 4.3, if that helps.
| Quote: | To me it isn't clear at all whether a powermac and a powermac g3 produce
compatible formats.
|
Well I assume they are _close_ anyway, given differences between
Rhapsody/OpenStep's archiver and NetBSD's. I assume that these are
likely to be fairly minor, with the compression likely to be the only
thing that really changed over that period.
| Quote: | If a tape has a SCSI interface then it usually is supported. Much like
all SCSI disks are supported whenever any are supported.
|
Excellent, it is SCSI.
| Quote: | Likely as not NetBSD will allow you to read the tape (eg using dd) IFF
you know the right blocking factor, but whether its tar can read the
contents of the archive I can't say.
|
Ok, well it sounds like this is the most likely solution anyway. So
I'll put NetBSD on the machine and come back to the technical issues of
actually reading the tape later.
So, a question about the install, the install guide for the macppc
version is extremely technical, and points to a page on "output-device
/chaos/control". I read this page, but it's essentially gobblygook --
although it claims to be for newbiews, it fails to identify what
exactly the problem is, how to tell if you've got it, or when/where/how
to go about running the 'upgrade'.
So does anyone know what the reference to /chaos/control means exactly?
It seems to have something to do with output-device, but the only
references I can find to that are on another unclear page about
OpenFirmware setup. Do I actually have to DO anything, or is this
purely informational?
Maury |
|
| Back to top |
|
|
jpd
*nix forums Guru
Joined: 22 Feb 2005
Posts: 877
|
| Posted: Fri Oct 28, 2005 12:23 am Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
Begin <1130415622.777773.214530@f14g2000cwb.googlegroups.com>
On 2005-10-27, Maury Markowitz <maury_markowitz@hotmail.com> wrote:
| Quote: | The tape (holding it now) is a 4mm DL 90m. I assume the 90m is the
length, and thus unimportant.
|
That is _not_ DLT, as you wrote before. It sounds rather like DAT.
| Quote: | The archive was created using Rhapsody, I believe I used whatever the
most simple and basic possible Unix command to put it onto the tape, I
think it's tgz format written out using dd (??).
[...]
I do not know what "blocking factor" is, so I assume "the default".
Rhapsody was essentially BSD 4.3, if that helps.
[,,,]
Well I assume they are _close_ anyway, given differences between
Rhapsody/OpenStep's archiver and NetBSD's. I assume that these are
likely to be fairly minor, with the compression likely to be the only
thing that really changed over that period.
|
At this point I would stop assuming anything, and start finding out
what it is that I'm talking about. But hey, that's just me.
| Quote: | If a tape has a SCSI interface then it usually is supported. Much like
all SCSI disks are supported whenever any are supported.
Excellent, it is SCSI.
|
Note again that this only talks about accessing the drive. Getting
the data off it in a meaningful way is something else entirely.
| Quote: | So, a question about the install, the install guide for the macppc
version is extremely technical, and points to a page on "output-device
/chaos/control". I read this page, but it's essentially gobblygook --
although it claims to be for newbiews, it fails to identify what
exactly the problem is, how to tell if you've got it, or when/where/how
to go about running the 'upgrade'.
So does anyone know what the reference to /chaos/control means exactly?
It seems to have something to do with output-device, but the only
references I can find to that are on another unclear page about
OpenFirmware setup. Do I actually have to DO anything, or is this
purely informational?
|
I don't know much about macs and running NetBSD on them, apart from
the fact that is _is_ rather more hairy than certain other platforms,
because they're setup with running macos in mind, and nothing else. But
I do know that you are apparently set to do that regardless, and as such
you can't go on until you've found out what all the gobblygook means.
--
j p d (at) d s b (dot) t u d e l f t (dot) n l . |
|
| Back to top |
|
|
Maury Markowitz
*nix forums beginner
Joined: 26 Oct 2005
Posts: 8
|
| Posted: Fri Oct 28, 2005 8:05 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
| Quote: | At this point I would stop assuming anything, and start finding out
what it is that I'm talking about. But hey, that's just me.
|
I do not understand what you are referring to. Are you referring to me
calling a DAT a DLT? Frankly this strikes me as a rather minor issue:
both machines have the same physical drive, the _name_ of that drive is
meaningless and only confused because I didn't have the actual tape in
my hand.
| Quote: | Note again that this only talks about accessing the drive. Getting
the data off it in a meaningful way is something else entirely. |
Well obviously. But since I put the data on using what is effectively
BSD 4.3 using the simplest possible command -- dd with gzip or
something similar, the issue here has little to do AT THIS POINT with
the data format, and absolutely everything with getting a system onto
the box that can talk to the drive.
Maury |
|
| Back to top |
|
|
Thor Lancelot Simon
*nix forums beginner
Joined: 27 Feb 2005
Posts: 13
|
| Posted: Sat Oct 29, 2005 4:17 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
In article <1130529955.538568.280860@g14g2000cwa.googlegroups.com>,
Maury Markowitz <maury_markowitz@hotmail.com> wrote:
| Quote: |
Well obviously. But since I put the data on using what is effectively
BSD 4.3 using the simplest possible command -- dd with gzip or
something similar, the issue here has little to do AT THIS POINT with
the data format, and absolutely everything with getting a system onto
the box that can talk to the drive.
|
If you don't know exactly how you put the data on the tape, it's very
very unlikely that you'll be able to read it back off without a huge
amount of experimentation -- if at all. In fact, if you did what you
describe above as "the simplest possible command" you may never be
able to get the data off the tape intact, because most tape drives
want fixed-length records by default and gzip does not produce those.
If I understand correctly, you used some program called "Rhapsody"
to make an archive file. I'll call it "c.rap". Then you did -- you
think -- something like this:
dd if=/tmp/c.rap | gzip -9 > /dev/nrst0
Or maybe you did this:
gzip -9 < /tmp/c.rap | dd of=/dev/nrst0
Or maybe you did this, based on one of your earlier comments:
tar csf /dev/nrst0 /tmp/c.rap
If the latter, you may have the most hope of recovering your data,
because tar uses a standard blocking factor of 10k. Unfortunately,
some drives can't write 10k blocks, so the data may have been
reblocked and you may have trouble reading them. Also, if you used
the "z" flag to tar, all bets are off, I think -- again, it compresses,
and the compressor does not block its output unless explicitly told to,
which tar -cz does not.
If you used the first command, you may have created a real mess for
yourself. Your only hope really is that the OpenStep tape device driver
reblocked the data for you to some standard size behind the scenes, or
that the tape drive itself could sanely handle variable-length records;
many can't. Also, if so much as a single bit of data on the tape has
been lost (not uncommon) the data won't decompress properly and you
won't be able to recover it.
If you used the second command, the tape will have been written with a
512 byte block size. You'll still have to pray that none of it was
lost (since you used host compression) but it should be possible to
recover it with "dd if=/dev/nrst0 | gzip -d > c.rap"; then you will
just have to deal with unpacking that c.rap file, however you plan to
do that. Except that if the OpenStep tape driver doesn't reblock, and
the tape drive you wrote on didn't reblock either, you may not be able
to ever read a tape written with 512-byte records, just as with the
variable-length records produced by the first command.
Finally, you will want to actually know what kind of tape you have, since
if it really is a DLT tape there are many different formats and older
drives can't read the newer formats. Yelling at someone who gave you
this helpful advice is pretty silly.
--
Thor Lancelot Simon tls@rek.tjls.com
"The inconsistency is startling, though admittedly, if consistency is to be
abandoned or transcended, there is no problem." - Noam Chomsky |
|
| Back to top |
|
|
Maury Markowitz
*nix forums beginner
Joined: 26 Oct 2005
Posts: 8
|
| Posted: Tue Nov 01, 2005 10:54 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
Excellent info, thanks. Just for clarification, Rhapsody is not a
program, but Apple's code name for what became OS X.
If I understand your comments correctly, the real problem here is the
block size issue. Reading your post now did trigger a memory, and I do
believe I used tar csf. But staying at the more theoretical side of
things, if I did manage to select settings that the drive could not
handle, what would happen in this case? Silent reblocking? If so, isn't
doing that considering the fact that you can't read it back off with
the same blocking factor a Really Bad Idea?
It really is a DAT. The only reason the term "DLT" appeared at any
point is that I confused the two TLA's. And it doesn't really make a
difference anyway, because the two drives are identical.
I didn't think I was "yelling" though!
Maury |
|
| Back to top |
|
|
Wolfgang.Schelongowski@gm
*nix forums beginner
Joined: 01 Aug 2005
Posts: 14
|
| Posted: Wed Nov 02, 2005 4:16 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
"Maury Markowitz" <maury_markowitz@hotmail.com> writes:
| Quote: | If I understand your comments correctly, the real problem here is the
block size issue. Reading your post now did trigger a memory, and I do
believe I used tar csf. But staying at the more theoretical side of
things, if I did manage to select settings that the drive could not
handle, what would happen in this case?
|
From my memory, albeit under Linux:
1) Errors
2) very sloooooow transport
depending on the blocksizes written/read.
Besides, for DATs you set the DAT tape blocksize via mt setbl or
whatever the man page of mt says (there are different varieties - GNU
mt differs from BSD mt). Try blocksizes 0, 512, and 10240. Test which
one copies the first 10MB from tape fastest, then use that setting.
| Quote: | It really is a DAT. The only reason the term "DLT" appeared at any
point is that I confused the two TLA's. And it doesn't really make a
difference anyway, because the two drives are identical.
|
I believe that the behaviour of DATs as to blocking is a bit
unusual when compared with other tapes. It might differ from that of
DLTs.
--
The first entry of Sin into the mind occurs when, out of cowardice or
conformity or vanity, the Real is replaced by a comforting lie.
-- Integritas, Consonantia, Claritas |
|
| Back to top |
|
|
Thor Lancelot Simon
*nix forums beginner
Joined: 27 Feb 2005
Posts: 13
|
| Posted: Wed Nov 02, 2005 6:17 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
In article <1130885663.167298.157190@z14g2000cwz.googlegroups.com>,
Maury Markowitz <maury_markowitz@hotmail.com> wrote:
| Quote: | Excellent info, thanks. Just for clarification, Rhapsody is not a
program, but Apple's code name for what became OS X.
If I understand your comments correctly, the real problem here is the
block size issue. Reading your post now did trigger a memory, and I do
believe I used tar csf.
|
You "used tar csf" to do *what*? To create the archive file on disk? Or
to write the archive directly to tape?
I'd be astonished if you used the "-s" switch to tar. Do you mean "cSf",
or perhaps "czf", or something else?
If you used tar to write the archive to tape you have 10k blocks on the
tape and it will probably work fine -- you can read it right back off
with tar x (in this case, probably tar xvf /dev/nrst0 though you may
want to do a tar tvf /dev/nrst0 first to see what you'are about to extract).
If you created the file on disk with tar and then wrote it to tape with
dd and dd's default blocksize of 512, all bets are off. While you might
be able to read it back on the _same_ system you wrote it on, there's no
real convention for _how_ to reblock such small writes, so the odds of
being able to read it back on any _other_ system are quite poor.
--
Thor Lancelot Simon tls@rek.tjls.com
"The inconsistency is startling, though admittedly, if consistency is to be
abandoned or transcended, there is no problem." - Noam Chomsky |
|
| Back to top |
|
|
Maury Markowitz
*nix forums beginner
Joined: 26 Oct 2005
Posts: 8
|
| Posted: Thu Nov 03, 2005 2:59 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
| Quote: | From my memory, albeit under Linux:
1) Errors
2) very sloooooow transport
depending on the blocksizes written/read.
|
Ok, that doesn't sound TOO fatal.
| Quote: | Try blocksizes 0, 512, and 10240. Test which one copies the
first 10MB from tape fastest, then use that setting.
|
Ok, cool.
Maury |
|
| Back to top |
|
|
Maury Markowitz
*nix forums beginner
Joined: 26 Oct 2005
Posts: 8
|
| Posted: Thu Nov 03, 2005 3:02 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
| Quote: | You "used tar csf" to do *what*? To create the archive file on disk?
|
Geez, I don't remeber. But what does seem to filtering in is that I
didn't use dd any any point. I seem to remeber typing in a single line,
with no pipes or redirection.
| Quote: | If you used tar to write the archive to tape you have 10k blocks on the
tape and it will probably work fine -- you can read it right back off
with tar x (in this case, probably tar xvf /dev/nrst0 though you may
want to do a tar tvf /dev/nrst0 first to see what you'are about to extract).
|
Ok, this is what I will try first.
In other news, I actually managed to find a copy of the original OS, so
I'm going to try an install with that first. The
commands/exploration/etc. shouldn't be much different that what you
have outlined above, Sadly the video output uses a DB-15, so I need
some sort of adaptor.
Maury |
|
| Back to top |
|
|
Maury Markowitz
*nix forums beginner
Joined: 26 Oct 2005
Posts: 8
|
| Posted: Sun Nov 06, 2005 2:33 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
Ok, some progress.
I was able to install the OS and found the tape drive at nrst0. mt
worked fine.
I then tried reading the file using tar and cpio, but both comlained
that the file format was unknown. So far this isn't so surprising.
Then I used dd to copy the file off the tape into my home dir. dd
happily did so, resulting in a suspiciously small 130k file. I am
curious about dd, exactly what does it do at a low level? Simply copy
bytes from dev1 to dev2? If so, how does it know when the file ends?
Anyway cat'ing the result was surprising. The tape had clearly readable
portions, which suggests that no compression was used on the archive. I
guess that is good news. However there are several hints that the
archive is not in a unix format at all, but created using some Mac
archiver (likely EMC's Retrospect).
The irony is that I installed the OS on top of a machine that used to
have Retrospect on it. That said, I tried using Retrospect on the tape
first (hoping it could read Unix tapes) and it failed.
*sigh*
Maury |
|
| Back to top |
|
|
Thor Lancelot Simon
*nix forums beginner
Joined: 27 Feb 2005
Posts: 13
|
| Posted: Mon Nov 07, 2005 4:33 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
In article <1131287639.814812.120460@f14g2000cwb.googlegroups.com>,
Maury Markowitz <maury_markowitz@hotmail.com> wrote:
| Quote: |
Then I used dd to copy the file off the tape into my home dir. dd
happily did so, resulting in a suspiciously small 130k file. I am
curious about dd, exactly what does it do at a low level? Simply copy
bytes from dev1 to dev2? If so, how does it know when the file ends?
|
The tape has end-of-file markers on it. It returns EOF to the reading
process every time it reaches one of those.
The 130k file you restored sounds like a table of contents from some
backup system that writes multiple backup files to one tape (in this
case, possibly just one, but with the table of contents in front). Have
you tried running "file" on it? (that is, on the file you restored from
tape with dd)?
--
Thor Lancelot Simon tls@rek.tjls.com
"The inconsistency is startling, though admittedly, if consistency is to be
abandoned or transcended, there is no problem." - Noam Chomsky |
|
| Back to top |
|
|
Maury Markowitz
*nix forums beginner
Joined: 26 Oct 2005
Posts: 8
|
| Posted: Tue Nov 08, 2005 6:20 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
No, I haven't tried file -- I'm pretty newbie to all of this so I'll
have to try that next.
BTW, there are things in the file I got that suggest it really is data.
In particular I saw strings of error messages from the "inside" of a
program that I recognize.
Someone suggested the easiest way to know for sure is to do another dd
with the block size set to some huge number and copies=1. That way I
get one ginourmous block, the length of which should tell me the block
size used by the backup software. I'm going to give that a try on the
weekend. He also noted that if the software uses variable-block-sizes
(which it can) then I'm in for some serious pain.
You know, after all of this I suddenly "get" open source.
Maury |
|
| Back to top |
|
|
igor@nospam.invalid
*nix forums addict
Joined: 17 Aug 2005
Posts: 81
|
| Posted: Wed Nov 09, 2005 5:51 pm Post subject:
Re: Rescueing a DLT tarball on a Mac
|
|
|
Maury Markowitz <maury_markowitz@hotmail.com> wrote:
| Quote: |
BTW, there are things in the file I got that suggest it really is data.
In particular I saw strings of error messages from the "inside" of a
program that I recognize.
|
Hello.
About two years ago I did a backup of SINIX-P, the operating system
that runs on my SNI RM-600 server (I do not trust a lot on tapes as
long-live storage devices). To make a full backup of the five tapes
of the operating system I used dd, until reached the end of the tape,
on the non-rewind device. Perhaps you can dump all these chunks on
numbered files and make some sense of them.
By the way, good luck with the recovery operation!
Cheers,
Igor. |
|
| Back to top |
|
|
Google
|
|
| Back to top |
|
|
|
|
The time now is Thu Jan 08, 2009 8:14 am | All times are GMT
|
|
MPAA | Mortgage Calculator | Debt Consolidation | Mortgage | Babb Fest
|
|
Copyright © 2004-2005 DeniX Solutions SRL
|
|
|
|
Other DeniX Solutions sites:
Unix/Linux blog |
electronics forum |
medicine forum |
science forum |
|
|
Privacy Policy
|
Powered by phpBB © 2001, 2005 phpBB Group
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
Forum index
»
*nix
»
BSD
»
NetBSD
