Subject: [netatalk-admins] tape backup to a mac

From: Danny Rice <[email-masked]>
Date: Fri, 14 May 1999 10:20:05 -0500 (EST)

Hello, I was wondering if there is a way to do tape backups from my
linux box to a tape drive connected to a mac.  The mac is connected to
the internet and on an apple talk network.  The tape drive is an APS
hyperdat 2 scsi.  The client software for backups on that mac is
retrospect 3.0.  I was thinking there might be something like "pap"
for doing tape backups.  That would be cool.

Danny Rice

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From: Bob Atkins <[email-masked]>
Date: Mon, 17 May 1999 14:06:30 -0700 (PDT)

> Sak Wathanasin wrote:
>
> In reply to Bob Atkins's message of the 17/05/99 at 00:44 -0700,
> 
> > While Retrospect may be a good product it is a proprietary product and
> > it is fairly expensive.
> 
> It's not cheap, but it's not that expensive either, and costs a lot less than
> losing all my data.
> 

I agree - I just don't like proprietary backup solutions.

> > A Mac backup application that uses the Unix rmt service
> > would be very simple to do
> 
> Oh, I don't know... You can probably do 90% easily, but then come the hard bits
> like backing up and restoring all the Finder info and the boot blocks. With
> Retrospect if you munge a disk, you can pull it out, put in a new one,
> low-level format it, do a volume restore and you have an exact copy of the
> pre-munged disk, including the icon and window positions of every file and
> folder, the AppleShare priviledges (if any) and the boot blocks*. Pulling off
> this trick with rmt would be interesting... I'm not saying it can't be done -
> Retrospect clearly can with its "FTP backup" -, only that it's not as easy as
> you make it out to be.
> 

Basically all the work you mention above would have to be part of Mac
backup application - rmt's role would be nothing more than the conduit
to/from the tape drive.

Actually rmt is pretty basic. You open the device, write any data you want in
any format you want and close the device. Think of rmt as just a simple
interface directly to the tape device connected to the Unix box. In terms
of writing and reading data from the tape it is 'blind', it doesn't care
how you format your data.

You could write a Mac backup tape using rmt take that tape and put in
in a device directly connected to a Mac system and read the *exact*
same data from the tape.

Here is an excerpt from rmt's man page - it really is very simple:

     The rmt program accepts requests that are  specific  to  the
     manipulation  of magnetic tapes, performs the commands, then
     responds with a status indication.   All  responses  are  in
     ASCII  and  in  one  of two forms.  Successful commands have
     responses of

          Anumber\n

     where number is an ASCII representation of a decimal number.
     Unsuccessful commands are responded to with

          Eerror-number\nerror-message\n

     where error-number is one  of  the  possible  error  numbers
     described  in intro(2), and error-message is the correspond-
     ing error string as printed from a call to perror(3C).   The
     protocol consists of the following commands:

          S\n            Return the status of the open device, as
                         obtained with a MTIOCGET ioctl call.  If
                         the operation was successful,  an  "ack"
                         is  sent  with  the  size  of the status
                         buffer, then the status buffer  is  sent
                         (in binary).

          Cdevice\n      Close the currently  open  device.   The
                         device specified is ignored.

          Ioperation\ncount\n
                         Perform a MTIOCOP ioctl(2) command using
                         the  specified  parameters.  The parame-
                         ters  are  interpreted  as   the   ASCII
                         representations of the decimal values to
                         place in the mt_op and  mt_count  fields
                         of the structure used in the ioctl call.
                         When the  operation  is  successful  the
                         return value is the count parameter.

SunOS 5.5           Last change: 14 Sep 1992                    1

rmt(1M)               Maintenance Commands                rmt(1M)

          Lwhence\noffset\n
                         Perform an lseek(2) operation using  the
                         specified   parameters.    The  response
                         value is returned from the lseek call.

          Odevice\nmode\n
                         Open  the  specified  device  using  the
                         indicated  mode.  device is a full path-
                         name, and mode is an  ASCII  representa-
                         tion  of  a  decimal number suitable for
                         passing to open(9E).   If  a  device  is
                         already  open, it is closed before a new
                         open is performed.

          Rcount\n       Read count bytes of data from  the  open
                         device.    rmt  performs  the  requested
                         read(9E) and responds with Acount-read\n
                         if the read was successful; otherwise an
                         error in standard  format  is  returned.
                         If  the  read  was  successful, the data
                         read is sent.

          Wcount\n       Write data onto the  open  device.   rmt
                         reads  count  bytes from the connection,
                         aborting if a premature EOF  is  encoun-
                         tered.   The  response value is returned
                         from the write(9E) call.

     Any other command causes rmt to exit.

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7 commands - its hard to get simpler.

There was a really good shareware backup program called SoftBackup for
the Mac which we use with a directly connected tape device. I wish I
could find the source code to it but it seems the orginal authors have
vanished. I was hoping to add an rmt capability to that program and it
would be a killer solution. If anyone knows where the source code can
be found for SoftBackup we would be 95% to an rmt solution.

---
Bob