[nSLUG] Re: rsync questions

Mike Spencer mspencer at tallships.ca
Wed Feb 23 03:44:07 AST 2011

I wrote re. password prompt using rsync:

me> Neither of those seems to work for me.  I'm still prompted in
me> either case.  What am I missing?

and Vlado Keselj <vlado at cs.dal.ca> replied:

vk> These passwords refer to the use of RSYNC server, and it seems
vk> that you are not using it.

Glimmer of clue appears.

vk> My approach is normally to set ssh password less access from one
vk> account a1 at h1 to a2 at h2 by copying the public key from a1 at h1
vk> (id_rsa.pub) to the file ~/.ssh/authorized_keys at a2 at h2, and then
vk> you can ssh, scp, or rsync without password back and forth from
vk> a1 at h1.

Ah!  I have to read the ssh manpage too.  Right.  I've only used ssh
for actual login where the password prompt is usual.  I didn't get  it
that it was ssh prompting me for a password.

I read the ssh manpage, did what Vlado (and the manpage) said.  Works

The Dan MacKay wrote:

Dan> I *do* use the rsync server, because it (well, mine does) runs as
Dan> root and can write files as root; so when I do a backup of files
Dan> from one machine to another, they have correct owners,
Dan> modification dates and permissions.

The -a switch seems to be doing all of that that I need.  All files are
owned by my primary username so maintaining owner is default.

Daniel Morrison <draker at gmail.com> added:

dm> An rsync server is also faster than using rsync over ssh, as you
dm> skip the encryption step. But you should do this only if you trust
dm> your local network....Since you are using NFS, you must trust your
dm> local network (right?)

Faster would be good because my router is old and slow (retained
because it has a parallel port for a print server).  As I write, rsync
is reporting between 500 and 600kB/sec using ssh.

My LAN is probably secure. My net connection is dial-up, not through
the same router that supports the LAN.  My wireless signal is only
usable at 150' or less (I've tested it) without better than average
antenna anyhow.  The nearest neighbor is way further than that. So
snoopers will have to be close enough (say, parked conspicuously in my
laneway) to risk my deployment of um.... analog countermeasures. :-)

dm> The default for rsync is to skip transfers of entire files if the
dm> file size and timestamp are the same.

That tidbit is mentioned only in passing in the manpage, under the
description of the -I flag.  I was wondering what rsync's notion of
"files are the same" was.

Initial backup transfer is taking forever.  In the future there will
not normally be GB quantities of update or new data.  So I'll see how
the first update goes over ssh.  If that, too, is tediously slow, I'll
run the daemon on DEST as a matter of course.

Rsync, like tar or gcc, is kinduva Swiss Army Knife.  It's very
helpful to get some pointers when all you want to do is slice

Thanks, all, for the help,
- Mike

Michael Spencer                  Nova Scotia, Canada       .~. 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^

More information about the nSLUG mailing list