/usr/bin/ssh not found when rsync is executed within rsnapshot

[Lorenz]

Hello,

yesterday i posted this issue on snapshot-discuss at listsourceforge.net (subject:
wondering why backup wont start), but after reading the FAQ and searching the
bugzilla DB i thought it could help to post here as well.

i have a problem. But let me first describe my setup. i followed this howto:

	http://dev.kprod.net/?q=linux-backup-rsnapshot-no-root

Now there is a backup server rpi-home and a remote host debx40. On both these
computers there is debian jessie (with rsnapshot version 1.3.1) installed, there
is a user backupuser and as far as i can see the remote login with password for
that user works:

backupuser at rpi-home ~ $ ssh debx40 -i ~/.ssh/id_rsa
Linux debx40 3.12-1-486 #1 Debian 3.12.9-1 (2014-02-01) i686
###some greeting lines###
$ whoami
backupuser

here is the result of
grep -v "#" /etc/rsnapshot | grep [a-z]
i.e. the /etc/rsnapshot minus the comments and the empty lines:

config_version	1.2
snapshot_root	/media/extfp/Backup/rsnapshot/test/
no_create_root	1
cmd_cp		/bin/cp
cmd_rm		/bin/rm
cmd_rsync	/usr/bin/rsync
cmd_ssh	/usr/bin/ssh
cmd_logger	/usr/bin/logger
retain		hourly	6
retain		daily	7
retain		weekly	4
verbose		5
loglevel	5
logfile	/var/log/rsnapshot.log
lockfile	/var/run/rsnapshot.pid
rsync_long_args	-ev --rsync-path=/home/backupuser/rsync-wrapper.sh
ssh_args	-i /home/backupuser/.ssh/id_rsa
link_dest	0
rsync_numtries	1
backup	backupuser at debx40:/	debx40/

and this is the content of /home/backupuser/rsync-wrapper.sh on the remote debx40.

#!/bin/sh

date >> /home/backupuser/backuplog
echo $@ >> /home/backupuser/backuplog
/usr/bin/sudo /usr/bin/rsync "$@";

in the /etc/sudoers there is a line

backupuser ALL=NOPASSWD: /usr/bin/rsync

when i enter e.g. sudo rsnapshot -D hourly on the backup server rpi-home i get this

require Lchown
Lchown module loaded successfully
Setting locale to POSIX "C"
echo 4702 > /var/run/rsnapshot.pid
mkdir -m 0755 -p /media/extfp/Backup/rsnapshot/test/hourly.0/
/usr/bin/rsync -av -ev --rsync-path=/home/backupuser/rsync-wrapper.sh \
    --rsh="/usr/bin/ssh -i /home/backupuser/.ssh/id_rsa" backupuser at debx40:/ \
    /media/extfp/Backup/rsnapshot/test/hourly.0/debx40/
rsync: Failed to exec /usr/bin/ssh -i /home/backupuser/.ssh/id_rsa: No such file or directory (2)
rsync error: error in IPC code (code 14) at pipe.c(85) [Receiver=3.1.0]
rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]
rsync error: error in rsync protocol data stream (code 12) at io.c(226) [Receiver=3.1.0]
----------------------------------------------------------------------------
rsnapshot encountered an error! The program was invoked with these options:
/usr/bin/rsnapshot -D hourly
----------------------------------------------------------------------------
ERROR: /usr/bin/rsync returned 12 while processing backupuser at debx40:/
/usr/bin/logger -i -p user.err -t rsnapshot /usr/bin/rsnapshot -D hourly: \
    ERROR: /usr/bin/rsync returned 12 while processing backupuser at debx40:/
touch /media/extfp/Backup/rsnapshot/test/hourly.0/
No directory to delete: /media/extfp/Backup/rsnapshot/test/_delete.4702
rm -f /var/run/rsnapshot.pid
/usr/bin/logger -i -p user.err -t rsnapshot /usr/bin/rsnapshot -D hourly: \
    ERROR: /usr/bin/rsnapshot -D hourly: completed, but with some errors

I suppose the important info is in that line

rsync: Failed to exec /usr/bin/ssh -i /home/backupuser/.ssh/id_rsa: No such file or directory (2)

but surprisingly to me: the Backup starts when i do

sudo /usr/bin/rsync -av -ev --rsync-path=/home/backupuser/rsync-wrapper.sh \
    --rsh="/usr/bin/ssh -i /home/backupuser/.ssh/id_rsa" backupuser at debx40:/ \
    /media/extfp/Backup/rsnapshot/test/hourly.0/debx40/

, which is the exact same command (copy-pasted from the rsnapshot output) that caused the error
in the first place. Except the sudo in front of it.

What could be the reason? How could i debug this?

--
kind Regards
Lorenz from Greifswald