Re: Bug#174525: ITP: dar -- Disk ARchive: Backup directory tree and files.
Brian May <firstname.lastname@example.org> writes:
> > > - ssh can be used for backups (just pipe the data via ssh to the
> > > destination file), for incremental backups (generate catalog at server
> > > and send it to client first). However, I am not certain about restores
> > > (client requires 2 pipes to server, one in each direction; this makes
> > > me nervous about potential deadlocks).
> > Shouldn't be a problem, just do "ssh client restore-comand" and then the
> > client's stdin and stdout are the two pipes you need. Gotta test it first of
> > course, but I expect it to work.
> That only brings STDOUT and STDIN to the local computer.
> The hard part will be doing:
> dar ... | ssh client darr_slave | dar ...
> where both dars represent the one process (so the above
> command line wont work).
Isn't this what named pipes are for?
dar ... < /tmp/darpipe | ssh client darr_slave > /tmp/darpipe
> I have heard that Bi-Directional communications like this is a risky,
> and buffering issues have caused big problems even for programs like
> rsync (hopefully resolved now).
True; unusual deadlocks can sometimes happen where one side is waiting
for the other side to read its data, but the reader side is gone. You
might try this if darr_slave suffers from that type of problem:
(dar ... ; cat > /dev/null) < /tmp/darpipe | \
ssh client darr_slave > /tmp/darpipe