> 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.
---
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
