Disaster Recovery and Rsync (was [lug] Commercial rsync service?)

Siegfried Heintze siegfried at heintze.com
Fri Feb 3 14:00:05 MST 2006

It sounds like we are back on the old disaster recovery topic again...

What are some favorite ways of using rsync with a remote repository
accessible over the public internet for the purposes of disaster recovery?

(1) Would you only use rsync on directories you are working in? It then
becomes your responsibility to remember which directories you have modified
files in. I've done this for years with zipping directories on CDs but it
scares me. And if you get hacked you still have to rebuild your system disk.

(2) Would you daily rsync everything including the /usr/bin, /bin,
/usr/local/bin, /etc, etc...? I guess you would use the find command to
exclude stuff in the /mnt directory so you would not include the entirety of
other devices on other machines.

(3) How do databases work? Do you have to stop the (for example) MySQL
deamon while you do the rsync? My guess is definitely. What about the
subversion or cvs deamons? Could this be a problem if you try to use a
single rsync command for an entire computer's local storage and it takes a
long time? It seems to me like you would want to have a lot of short shell
scripts to run daily so you don't have to shut down all your servers at once
for the entire duration of the synchronization.

(4) What about links? Creators of linux distros love links. Does rsync
properly reconstruct hard and soft links?

(5) Let us say you initially rsync the entirety of your local storage for a
software development computer that also doubles as prototyping web site
server and cvs/subversion repository. Maybe it is Saturday and you know you
have only altered one file. Could you rsync that directory only and would
rsync be smart enough to find that sub directory in the remote repository
instead of having to date compares on all the files for the entirety of your
local storage?

(6) I believe someone previously explained that one can boot from a LiveCD
and use rsync to restore your boot disk and then boot from the boot disk. I
guess I should give this a try before disaster strikes. To bad this won't
work for windows (NTFS) paritions (or will it?). Has anyone tried it? Can
you run rsync on a windows partition? If you were doing it for the purposes
of rebuilding a boot disk, I think you would want to do this at a block
level because special files like the windows registery cannot (I believe) be
simply copied. Sometime ago someone explained to me that they could zip an
entire Win95 boot disk and restore it with zip and expect to boot, but this
did not work with NT. I assume this is still true with XP.

Can rsync simply bypass the NTFS file system and do block level restores?
Perhaps there is some other utility?


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