New User Seeking Some Clarification
January 09, 2004 11:02AM
I am a new user and have a couple of questions I hope someone will be willing to take the time to answer.

I have read all the documentation I can find but I want to be sure I understand how rdiff-backup works.

As I understand it, rdiff creates a mirror directory which is not compressed or altered in any way from the source with the exception of adding the incremental information in sub-directories.

Then as I subsequently run rdiff it automatically updates the main file list with the latest files and then moves or copies previous versions of those files to the sub-directories containing the incremental data which is compressed.

And then I have the option of telling rdiff to go and delete incremental data from a certain point in time if I choose.

If that is it in a nutshell then this seems pretty easy to use and maybe I am trying to make it harder than it really is.

Assuming that is all correct here are my questions (please correct me if I have made any incorrect statements).

1. Is there a way to "archive" incremental data instead of just deleting it. Say if I am running out of room on my backup server I might want to just store the incremental data on CD ROM or yet another hard drive?

2. Can you restore to the file level or just the directory level? And can you backup to the file level or just the directory level?

3. It seems that rdiff doesn't need any special runtime parameters to do an incremental backup. It seems automatic. Is that correct? I just backup from the same source to the same target as my first backup?

4. I am backing up web servers to a remote backup server with this so I need daily backups with at least a week worth of incrementals. This seems to easy. Does anyone have any practical advice for this type of scenario? Anything I need to take precaution of or anything special I should do. I am worried that until I have a fatal crash I won't really know how good or bad my backup solution is.

5. I have Plesk (a web server administration software package) installed if anyone knows what that is. It has a dump utility with it but I would have to come up with my own rotation scheme to work out incremental backups. Anyone have any experience comparing dumps with rdiff.

Thanks.

Chris Young
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Synergy Point[/b]
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New User Seeking Some Clarification
January 09, 2004 01:29PM
On Fri, 9 Jan 2004 12:15:28 -0500
"Chris Young" <ChrisYoung < at > SynergyPoint.net> wrote:

[quote]As I understand it, rdiff creates a mirror directory which is not
compressed or altered in any way from the source with the exception of
adding the incremental information in sub-directories.
[/quote]
That's correct. For each directory tree you backup, there will be an
'rdiff-backup' directory added to the mirror, but other than that
directory the backup is an exact mirror.

[quote]Then as I subsequently run rdiff it automatically updates the main
file list with the latest files and then moves or copies previous
versions of those files to the sub-directories containing the
incremental data which is compressed.
[/quote]
Yes, although more accurately it puts the _differences_ of previous
versions into the increment directories.

[quote]And then I have the option of telling rdiff to go and delete
incremental data from a certain point in time if I choose.
[/quote]
Yes.

[quote]1. Is there a way to "archive" incremental data instead of just
deleting it. Say if I am running out of room on my backup server I
might want to just store the incremental data on CD ROM or yet another
hard drive?
[/quote]
Not easily, so far as I'm aware, but others may know of a way.

[quote]2. Can you restore to the file level or just the directory level? And
can you backup to the file level or just the directory level?
[/quote]
You can only backup and restore at the directory level.

[quote]3. It seems that rdiff doesn't need any special runtime parameters to
do an incremental backup. It seems automatic. Is that correct? I just
backup from the same source to the same target as my first backup?
[/quote]
That is correct.

[quote]4. I am backing up web servers to a remote backup server with this so
I need daily backups with at least a week worth of incrementals. This
seems to easy. Does anyone have any practical advice for this type of
scenario? Anything I need to take precaution of or anything special I
should do. I am worried that until I have a fatal crash I won't really
know how good or bad my backup solution is.
[/quote]
As with any backup solution, you'd be well advised to perform 'test'
restores. However, to answer your question, no, there is nothing special
you have to do.

[quote]5. I have Plesk (a web server administration software package)
installed if anyone knows what that is. It has a dump utility with it
but I would have to come up with my own rotation scheme to work out
incremental backups. Anyone have any experience comparing dumps with
rdiff.
[/quote]
I don't. However, I would just use rdiff-backup to backup the data
separately from the built-in dump mechanism. Of course, you could do
both (independently) if you wanted a backup-backup, as it were.

I have a short bash script that I run from a cron job to back up a
number of systems using rdiff-backup. I don't make any claim for it
other than'it works for me', but if you'd like a copy then drop me
personal mail.

Keith
New User Seeking Some Clarification
January 09, 2004 10:24PM
On Fri, Jan 09, 2004 at 12:15:28PM -0500, Chris Young wrote:
[quote]I am a new user and have a couple of questions I hope someone will be
willing to take the time to answer.

I have read all the documentation I can find but I want to be sure I
understand how rdiff-backup works.

As I understand it, rdiff creates a mirror directory which is not
compressed or altered in any way from the source with the exception of
adding the incremental information in sub-directories.

Then as I subsequently run rdiff it automatically updates the main file
list with the latest files and then moves or copies previous versions of
those files to the sub-directories containing the incremental data which
is compressed.

And then I have the option of telling rdiff to go and delete incremental
data from a certain point in time if I choose.
[/quote]
Yup, that's pretty much exactly how it works :)

I'm just a user, but I'll try to help out with your questions as best I
can.

[quote]2. Can you restore to the file level or just the directory level? And
can you backup to the file level or just the directory level?
[/quote]
Yup, you can back up a directory, file, or a selection thereof, same as
with restore. See the FILE SELECTION section in the man page for
details about how to include/exclude files or directories or dir trees.
This is probably the hardest part of setting up your backups IMHO, but
it's not *that* hard.

[quote]3. It seems that rdiff doesn't need any special runtime parameters to do
an incremental backup. It seems automatic. Is that correct? I just
backup from the same source to the same target as my first backup?
[/quote]
Exactly. Rdiff-backup will read the rdiff-backup-data directory and see
when the last snapshot was and go from here.

[quote]4. I am backing up web servers to a remote backup server with this so I
need daily backups with at least a week worth of incrementals. This
seems to easy. Does anyone have any practical advice for this type of
scenario? Anything I need to take precaution of or anything special I
should do. I am worried that until I have a fatal crash I won't really
know how good or bad my backup solution is.
[/quote]
I'm sure there are books written on this subject, but my backup script
looks something like this:

rdiff-backup $INCLUDES --exclude / / alan < at > backupserver::/backups/server
rdiff-backup --remove-older-than 7D --force alan < at > backupserver::/backups/server

First backup specific files ($INCLUDES) from the root of the filesystem
(/) but not all of / (exclude /) to the backupserver. Then remove any
backups older than 7 days.

Obviously some things have been snipped out, but after watching it for a
couple of days to make sure it was doing what I wanted, it just keeps on
going and doing what I want :)

When I have had a crash I cheat a bit and just copy the entire directory
(excluding the rdiff-backup-data) directory back onto the server and I'm
back in business (I actually have a local backup and a remote back up so
I didn't have to scp all the files back).

[quote]5. I have Plesk (a web server administration software package) installed
if anyone knows what that is. It has a dump utility with it but I would
have to come up with my own rotation scheme to work out incremental
backups. Anyone have any experience comparing dumps with rdiff.

[/quote]
What data is dumped? Rdiff-backup can do diffs of binary or text files,
so it'd be able to diff the dumps fine.

However, I found a bit of a gotcha. When I moved from tar/scp to
rdiff-backup I was dumping my database everynight to a .sql file and
then bziping it and including that in my nightly tar. When I moved to
rdiff-backup I left it like that until I realized that because of the
bzip the .sql file was completely different each time, so the entire
file was transfered as an increment. When I removed the bzip part of
the process the base file was larger, but the increments were much
smaller because they were simply text diffs of new/changed data, not a
binary diff of an entirely changed file. Something to think about
anyway.

alan

--
Alan <alan < at > ufies.org> - http://arcterex.net
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