Backup Problem

[Jie Li]

The error message says "Can't open /dev/tty to prompt for more media."

What can cause this kind of problem?

Thanks in advance

[Peter Godron · Accepted solution]

Hi,
sounds to me as if you have run out of tape space and a second tape is needed.
In order to prompt for the tape, a message is put to the terminal and once the new tape is loaded the operator is asked to press Y to continue.
In your case no terminal to write to was found.

[A. Clay Stephenson]

If you started a backup with nohup (or cron) there is no controlling terminal associated with the process and when the process attempted to open the pseudodevice /dev/tty (which will automatically connect to "your" terminal no matter on which actual device "you" are logged in), it failed. The backup continued until all the media on the device(s) listed on the command line were used and then tried to prompt for more media.

[Jie Li]

We have 2 mirrored harddrives 17 GB each. Our tape is 40 GB compressed. Would it be enough capacity?

[Peter Godron]

Hi,
do you mean 34Gb to be backed up or 17Gb ( as it is mirrored)?

If you are backing up 34Gb onto a 40Gb compressed tape and the compression rate is not high enough you may get this error. What is the native (uncompressed) cpacity of the tape?

[Jie Li]

The native capacity is 20 gig. How do you find out if you actually backup 34 gb or 17 gb?

Thanks

[Michael Steele_2]

Need the tape drive model number and product number

[Jie Li]

Product#: C4318SZ#110

The followings are commands and outputs that I used.

By the way, I got error message right away even when I only tar a small file to the tape.

# diskinfo /dev/rmt/0m
SCSI describe of /dev/rmt/0m:
vendor: HP
product id: C5683A
type: sequential access
size: 20041365 Kbytes
bytes per sector: 1024
# dd if=/etc/host of=/dev/rmt/0m
/etc/host: No such file or directory
dd: cannot open /etc/host
# dd if=/etc/hosts of=/dev/rmt/0m
I/O error
1+0 records in
0+1 records out
# ioscan -fnC tape | more
Class I H/W Path Driver S/W State H/W Type Description
=====================================================================
tape 0 0/0/1/0.6.0 stape CLAIMED DEVICE HP C5683A
/dev/rmt/0m /dev/rmt/0mnb /dev/rmt/c0t6d0BESTn /dev/rmt/c0t6d0DDSb
/dev/rmt/0mb /dev/rmt/c0t6d0BEST /dev/rmt/c0t6d0BESTnb /dev/rmt/c0t6d0DDSn
/dev/rmt/0mn /dev/rmt/c0t6d0BESTb /dev/rmt/c0t6d0DDS /dev/rmt/c0t6d0DDSnb

[A. Clay Stephenson]

This indicated that dd wrote normally because it wrote 0 complete 512-byte blocks and 1 partial 512-byte block.

# dd if=/etc/hosts of=/dev/rmt/0m
I/O error
1+0 records in
0+1 records out

I am surprised that diskinfo works on a tape drive; it would not even have occurred to me to run the command. In any event, I suspect that you are using an incompatible tape. What does "mt -f /dev/rmt/0m status" report when a tape is inserted in the drive?

Note that tar under HP-UX writes in 10KiB blocks so if you wish to reblock using dd, you must specify a ibs=10k and obs must be a multiple of 10k.

[Jie Li]

Why it says I/O error?

[A. Clay Stephenson]

Sorry, you are correct. You should always echo "${?}" after each command to capture the exit status; in this case =, it was probably 5 indicating an i/o error. I suggest that you try running tar with a brand new tape that is DDS-4 compatible.

[Jie Li]

It was a hardware problem. The tape drive is broken. HP sent someone to replace the drive. It works now. Thanks for all your help.