[Rdiff-backup-bugs] [sr #107697] rdiff-backup fails with forced-command but works through shell

[anonymous]

URL:
  <http://savannah.nongnu.org/support/?107697>

                 Summary: rdiff-backup fails with forced-command but works
through shell
                 Project: rdiff-backup
            Submitted by: None
            Submitted on: Wed 25 May 2011 09:32:15 AM UTC
                Category: None
                Priority: 5 - Normal
                Severity: 4 - Important
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
        Operating System: GNU/Linux

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Details:


I am stuck. I have read HOWTOs all over the place saying how to get
rdiff-backup to use a public key with a 'command="(shell script name)"'. The
script then executes the client side version of rdiff-backup sudo'd which then
safely backups up everything.  Here is the HOWTO that explains what I am
trying to do in detail (for rsync but I’m trying to do it for rdiff-backup):
http://troy.jdmz.net/rsync/index.html

 

I can do this (with ridff-backup) using public-key authentication as root on
the client with the forced command in the key on the client side. But I just
CANNOT get the forced-command in a script to work with rdiff-backup.

 

BTW, I can get the forced-command to work calling a script merely containing
the 'ls' command.  Maybe this all has something to so with the shell messing
with STDOUT and potential fundamental misunderstanding of shell environments
as hinted at here:
http://www.mail-archive.com/address@hidden/msg02954.html

?

 

What Works

 

Currently 'rdiff-backup' works great on the client/backup-machine with the
command:

 

rdiff-backup address@hidden::/home/user /home/server-backups/user

 

The login uses a password-less key-based authentication and the ssh
client-side configuration (.ssh/config) file reading:

 

host client

    hostname client

    user user

    identityfile /home/client/key/server-passwordless-key

    compression yes

    protocol 2

 

NOTE: they private key is in /home/client/key/server-password-less-key.

 

On the server the public-key starts with the following constraints:

 

from="client",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty,command="rdiff-backup
--server --restrict-read-only /" ssh-rsa AAasdfaj23jasljjj..etc., etc.

 

This works perfectly. Both machines are Ubuntu Server 10.04 LTS.

 

 

The Error

 

The problem is that if I want to "force the command" on the server by altering
the server-side public key so it looks for '/usr/local/bin/hard-coded-rdiff'
as follows:

 

  
from="client",no-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty,command="/usr/local/bin/hard-coded-rdiff"
ssh-rsa AAasdfaj23jasljjj..etc., etc.  

 

I have run:

 

chmod 744 /usr/local/bin/hard-coded-rdiff

 

...so it should be executable by all. 'user' can execute
/user/local/bin/hard-coded-rdiff.

 

/usr/local/bin/hard-coded-rdiff's contents are:

 

#! /usr/bin/sh

/usr/bin/rdiff-backup --server --restrict-read-only /

 

This fails on the client with the message:

 

Exception '' raised of class '<type 'exceptions.MemoryError'>':

File "/usr/lib/pymodules/python2.6/rdiff_backup/Main.py", line 304, in
error_check_Main

  try: Main(arglist)

File "/usr/lib/pymodules/python2.6/rdiff_backup/Main.py", line 321, in Main

  rps = map(SetConnections.cmdpair2rp, cmdpairs)

File "/usr/lib/pymodules/python2.6/rdiff_backup/SetConnections.py", line 76,
in cmdpair2rp

  if cmd: conn = init_connection(cmd)

File "/usr/lib/pymodules/python2.6/rdiff_backup/SetConnections.py", line 152,
in init_connection

  check_connection_version(conn, remote_cmd)

File "/usr/lib/pymodules/python2.6/rdiff_backup/SetConnections.py", line 160,
in check_connection_version

  try: remote_version = conn.Globals.get('version')

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 450, in
__call__

  return apply(self.connection.reval, (self.name,) + args)

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 368, in
reval

  result = self.get_response(req_num)

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 315, in
get_response

  try: req_num, object = self._get()

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 240, in
_get

  data = self._read(length)

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 210, in
_read

  try: return self.inpipe.read(length)

 

Traceback (most recent call last):

 

File "/usr/bin/rdiff-backup", line 30, in <module>

  rdiff_backup.Main.error_check_Main(sys.argv[1:])

File "/usr/lib/pymodules/python2.6/rdiff_backup/Main.py", line 304, in
error_check_Main

  try: Main(arglist)

File "/usr/lib/pymodules/python2.6/rdiff_backup/Main.py", line 321, in Main

  rps = map(SetConnections.cmdpair2rp, cmdpairs)

File "/usr/lib/pymodules/python2.6/rdiff_backup/SetConnections.py", line 76,
in cmdpair2rp

  if cmd: conn = init_connection(cmd)

File "/usr/lib/pymodules/python2.6/rdiff_backup/SetConnections.py", line 152,
in init_connection

  check_connection_version(conn, remote_cmd)

File "/usr/lib/pymodules/python2.6/rdiff_backup/SetConnections.py", line 160,
in check_connection_version

  try: remote_version = conn.Globals.get('version')

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 450, in
__call__

  return apply(self.connection.reval, (self.name,) + args)

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 368, in
reval

  result = self.get_response(req_num)

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 315, in
get_response

  try: req_num, object = self._get()

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 240, in
_get

  data = self._read(length)

File "/usr/lib/pymodules/python2.6/rdiff_backup/connection.py", line 210, in
_read

  try: return self.inpipe.read(length)

MemoryError

 

The message from rdiff-backup on the server (pulling from client) ends with a
dump of errors from the python executable and a "memory error."   Same command
on the client, small change to force the user of a shell script on the server
and it fails – why please?

 

Thanks for your suggestions.

 

Respectfully,

Richard

 

P.S. I also listed this question on serverfault.com here:
http://serverfault.com/questions/271518/rdiff-backup-fails-with-forced-command-but-works-through-shell
if you want to answer the question for points there.  






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