SUMMARY: tar -rf /dev/rmt/0 => I/O error

Dear Sun managers,

First it looks a lot of actual tape devices don't support tar appending (the
'r' and 'u' parameters).
In my case and for my Tandberg DLT100 I think it was confirmed by the
messages in /var/adm, which reported an "Illegal request" error straight
right from the hardware driver.

Tar appending shouldn't be confused with adding another tar file on the
tape, what can be done with the "no-rewind" driver (/dev/rmt/0n). So, I had
no other choice than to do this way, and to play with the 'mt' command to
seek back and forth on the tape.

This has already been covered in Sunmanager.org and the summary is archived:
http://www.sunmanagers.org/archives/1999/0048.html

However, care must be taken to always know where on the tape we are to avoid
overwriting previously saved stuff, or to avoid unexpected device's errors
in scripts as I just have experienced.

Also, upon the others suggestion, I quickly had a look at GNU's gtar, which
"append and update" features also failed with my tape device. gtar has a new
GNU-format incremental backup feature (-g switch), which I tried to make
appending incremental archives to my tape, but it failed as well. I'm not
sure this feature works with tapes... As I was short with time, I abandoned
this lead.


Many thanks for their help to:
Rene Occelli
Bill R. Williams
Jay Lessert
Mark Andrews
Karl Vogel
and to Bill Fenwick for having made the above mentioned summary.

Best regards, Eric Voisard


> -----Original Message-----
> I think this is a classical one:
> When I try to append files to a tape backup with tar, it fails,
> either with
> an "I/O error" or a "write error"
>
> I've read that some tape devices don't support tar's appending, so how do
> you manage appending files or updating a directory structure to a tape
> backup on Solaris, if possible by using Solaris tools...
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