SUMMARY: Copying from disk to disk

From: Simon Gibbons (
Date: Tue Jul 02 1996 - 05:08:07 CDT

Dear Sun-Managers,

Last month I requested some help regarding dd and the steps involved in
increasing the size of a partition on a system disk (original message
included at end). As usual, Sun-Managers were extremely helpful. Many
thanks to:

Brion Leary
Dave Zavaston
Don Cockman
Mike Cross
Jeff Wasilko
Herbert Wengatz
Cecil Pang
Greg Kranz
Thang Victor Dinh
Mark S. Anderson
Virginia Coffindaffer
Danny Johnson
George Goffe
Dougal Scott
Mike Burton
Stephen Richardson
Bill Holzapfel
... and anyone I have neglected to mention.

A few good points came out of the answers:

1. dd will ONLY work on disks of the same geometry.

2. only use dd on the raw device, i.e. /dev/rdsk/...

3. many Sun-managers who responded preferred dump and restore, partition
by partition - and this turned out to be the best result since I found
my two disks were not of equal geometry.

4. many also suggested that I boot single-user from CD-ROM and work from
there - very good advice which I used.

5. recommended block sizes for dd:
                        ... and the one I really like: 512 times (no. of sectors per track)

I'm not an experienced System Administrator, so these kind of
suggestions were extremely valuable. Thanks again,


Original Question:
> Dear Sun-Managers,
> I want to increase the /var partition on the system disk of a
> SPARCserver20 running Solaris 2.4. The steps I'm planning to take are
> (i) copy system disk to spare disk, (ii) boot from spare disk, (iii)
> repartition the system disk, and (iv) boot from system disk.
> I'm stuck at step one. I'd like to use dd to copy from one disk to
> another, but I can't seem to find any info on the block size I should
> be using. Does anybody know how to work this out? Also, can I use dd
> to copy from the _mounted_ system disk to an _unmounted_ disk (but
> still in the SCSI chain)?
> Many thanks in advance, and I will summarise.
> Simon
> Simon Gibbons
> Technology Services Officer
> Australian Institute of Family Studies
> Melbourne, Australia
> Tel: 61-3-9214 7880
> Fax: 61-3-9214 7839

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