Backup Central

When using rdiff-backup (which I have not yet done) is it necessary that all remote machines have the same users as the local machine? Moreover, do each of these users and groups on remote machines have to have the same UID and GID?

On Sun, 2006-02-12 at 16:27 -0600, Benjamin Podoll wrote:
When using rdiff-backup (which I have not yet done) is it necessary
that all remote machines have the same users as the local machine?
Moreover, do each of these users and groups on remote machines have to
have the same UID and GID?

Another question - is there any analogy for rsync's --numeric-ids?
Making full backup of the the system, I prefer to preserve numeric IDs.
According to man page, I can provide mapping files, but what if just
want no mapping at all?


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--
Vadim Kouzmine <kouzminv < at > gmail.com>

Vadim Kouzmine wrote:
When using rdiff-backup (which I have not yet done) is it necessary
that all remote machines have the same users as the local machine?

No.

Moreover, do each of these users and groups on remote machines have to
have the same UID and GID?

No.

Another question - is there any analogy for rsync's --numeric-ids?
Making full backup of the the system, I prefer to preserve numeric IDs.
According to man page, I can provide mapping files, but what if just
want no mapping at all?

This is free software. You need to try it out. If you have problems when
you do, we'll help. The price you pay for free software is either you
read the documentation and experiment or you pay (real money) and have
someone set it up for you.

Good luck!

Keith

--
Keith Edmunds

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On Mon, 2006-02-13 at 01:23 +0000, Keith Edmunds wrote:

Vadim Kouzmine wrote:
I'm sorry, two questions below were not mine:

When using rdiff-backup (which I have not yet done) is it necessary
that all remote machines have the same users as the local machine?

No.

Moreover, do each of these users and groups on remote machines have to
have the same UID and GID?

No.


This was my question:

Another question - is there any analogy for rsync's --numeric-ids?
Making full backup of the the system, I prefer to preserve numeric IDs.
According to man page, I can provide mapping files, but what if just
want no mapping at all?


Let me explain why I asked this.
I re-read man page many times. I learned that default behavior is:
- map user/group names and fall back to numeric IDs if no match;
- provide mapping files to change default mappings.

There is no easy option to just store numeric IDs as is. Please correct
me if I'm wrong.

I can imagine (actually I deal with) two situations like these:
- I backup through ssh to remote/different server running may be
different distro and don't want UID/GID to be mapped;
- I restore from remote backup on the host I just booted from some (any)
live CD, and don't want IDs be messed up on either backup or restore
side.

Indeed I don't see any reason to map UID/GID in a backup. If we preserve
devices/mtime/ctime/whatever - why mapping user/group by default?

Having just simple option like --numeric-ids can be useful for some
group of users.

This is free software. You need to try it out. If you have problems when
you do, we'll help. The price you pay for free software is either you
read the documentation and experiment or you pay (real money) and have
someone set it up for you.
I thought free software needs user opinions. rdiff-backup is a great
product, irreplaceable in some aspects, and all I want just to help to
make it better.

Thanks,
Vadim


Good luck!

Keith

--
Vadim Kouzmine <kouzminv < at > gmail.com>

Vadim Kouzmine wrote:
Let me explain why I asked this.
I re-read man page many times. I learned that default behavior is:
- map user/group names and fall back to numeric IDs if no match;
- provide mapping files to change default mappings.

Sorry, I didn't realise that the first two questions were not from you.
My point, however, remains: a couple of hours TRYING this would show you
how it works. However: if rdiff-backup does not have root privileges on
the machine receiving the backup then it will store UID/GID data as part
of the metadata. Upon restoring a file, it will restore the UID/GID.
There is no need to map UID/GID on the system receiving the backup under
normal circumstances.

There are many ways of doing this in practice. One way - the way I do it
- is to have the backup process run as root on the source machines so
that it can read all files, but to run it as a non-privileged user on
the backup server (receiving the backup). Restoration works exactly the
same way, and UID/GID is restored.

Keith

On Mon, 2006-02-13 at 08:40 +0000, Keith Edmunds wrote:

My point, however, remains: a couple of hours TRYING this would show you
how it works. However: if rdiff-backup does not have root privileges on
the machine receiving the backup then it will store UID/GID data as part
of the metadata. Upon restoring a file, it will restore the UID/GID.

There is no need to map UID/GID on the system receiving the backup under
normal circumstances.

Exactly. There is no need in it!

I understand your point here - if backup receiver is a non-privileged
user, then no mapping takes place. Right.

But what if backup receiver is a root? [let's skip the discussion why
running under root consider harmful ]
If backup is made under root privileges, then mapping files look to be
the only way to preserve original numeric UID/GID. Am I right here?

Compare rdiff-backup, tar and rsync: all three map UID/GID by default
and fall back to numeric ID when name has no match. But rsync has
--numeric-ids, and tar has --numeric-owner. rdiff-backup has ???

I assume there are other users like me who will benefit of having exact
copy of source on the backup size. I admit that ACL add complexity here.

Vadim



There are many ways of doing this in practice. One way - the way I do it
- is to have the backup process run as root on the source machines so
that it can read all files, but to run it as a non-privileged user on
the backup server (receiving the backup). Restoration works exactly the
same way, and UID/GID is restored.

Keith
--
Vadim Kouzmine <kouzminv < at > gmail.com>

Vadim Kouzmine wrote:

Compare rdiff-backup, tar and rsync: all three map UID/GID by default
and fall back to numeric ID when name has no match. But rsync has
--numeric-ids, and tar has --numeric-owner. rdiff-backup has ???

Forgive me if you've already investigated this, but did you try
--preserve-numerical-ids ?

From the man page:
If the --preserve-numerical-ids option is given, the remote
files will always have the same uid and gid, both for ownership
and ACL entries. This may cause unames and gnames to change.


Andrew

--
Andrew Ferguson - owsla < at > princeton.edu

On Mon, 2006-02-13 at 12:47 -0500, Andrew Ferguson wrote:
Vadim Kouzmine wrote:

Compare rdiff-backup, tar and rsync: all three map UID/GID by default
and fall back to numeric ID when name has no match. But rsync has
--numeric-ids, and tar has --numeric-owner. rdiff-backup has ???

Forgive me if you've already investigated this, but did you try
--preserve-numerical-ids ?
Oh, excuse silly me. I haven't tried development version, stopped on
stable 1.0.4. This explains everything and I'm happy now!

Thanks Andrew for pointing me there!

Vadim

Vadim Kouzmine wrote:
Oh, excuse silly me. I haven't tried development version, stopped on
stable 1.0.4. This explains everything and I'm happy now!

the only other point to note is that in the past, some options weren't
in the man pages for some reason. at any one time a full list of options
relevant to your version can be obtained by reading Main.py that comes
with rdiff-backup. on my system thats at
/usr/lib/python2.4/site-packages/rdiff_backup/Main.py

dave