Re: [rdiff-backup-users] rdiff-backup restore from read-only file system

[dean gaudet]

On Sat, 29 Jul 2006, Chris Connett wrote:

> On 7/24/06, dean gaudet <address@hidden> wrote:
> > it's not supported yet... patches welcome.
> 
> OK, I've written a simple patch to use the tempfile module out of the
> standard library.  I've written it to maintain compatibility with
> Python 2.2, which appears to be this project's compatibility target.
> I had to use the module in a slightly unorthodox manner, to keep the
> interface the same.  Patch is against latest CVS.  Comments welcome.

thanks... but i'm not sure this is going to work... note the comment for 
the function you modified:

def new_in_dir(dir_rp):
        """Return new temp rpath in directory dir_rp"""

i'm pretty sure that function is called in situations where rdiff-backup 
needs a temp file on the same filesystem as a particular directory -- so 
that it can be renamed.


TempFile.new also uses TempFile.new_in_dir... and look at the callers:

% grep TempFile.new *.py
Rdiff.py:       tf = TempFile.new(rp)
backup.py:              tf = TempFile.new(mirror_rp)
backup.py:              self.dir_replacement = TempFile.new(base_rp)
backup.py:              tf = TempFile.new(mirror_rp)
fs_abilities.py:                subdir = TempFile.new_in_dir(rbdir)
journal.py:             entry_rp = TempFile.new_in_dir(journal_dir_rp)
regress.py:     temprp = TempFile.new_in_dir(Globals.rbdir)
regress.py:                     tf = TempFile.new(rf.mirror_rp)
restore.py:             tf = TempFile.new(rp)
restore.py:             self.dir_replacement = TempFile.new(base_rp)


for your needs w.r.t. restore you probably want to audit the uses in 
restore.py and see if the can be changed to use a non-local inode.

i suspect you're going to have some troubles with fs_abilities... although 
i don't really think it should need to know the mirror fs abilities when 
it's doing a restore... because it should be extracting everything it 
needs from the metadata.  but i'm not 100% hopeful that will work 
properly.

btw when testing this patch you probably want to test a bunch of 
variations:

- local->local; local->remote; remote->local
- backup, restore, regress
- TMPDIR pointing to different fs (for maximum breakage -- no need to 
  point it at the same fs... if everything works on a different fs we're 
  probably fine)

note that if you want to script this sort of testing you can test a 
"remote" end without using ssh... this is effectively remote from 
rdiff-backup's point of view:

        rdiff-backup --remote-schema '%s' 'rdiff-backup --server'::src dst

that'll just open up a pipe to another rdiff-backup and it's equivalent to 
running it over ssh for most testing purposes.

thanks for looking at this...

-dean