Why is rsync not found?

Your .profile is only read when you log in interactively. When rsync connects to another machine to execute a command, /etc/profile and ~/.profile are not read.

If your login shell is bash, then ~/.bashrc may be read (this is a quirk of bash — ~/.bashrc is read by non-login interactive shells, and in some circumstances by login non-interactive shells). This doesn't apply to all versions of bash though.

The easiest way to make rsync work is probably to pass the --rsync-path option, e.g.

rsync --rsync-path=/home/elbarna/bin/rsync -avP /home/user/.profile hpux3:/home/user/.profile

If you log in over SSH with key-based authentication, you can set the PATH environment variable via your ~/.ssh/authorized_keys. See sh startup files over ssh for explanations of how to arrange to load .profile when logging in over SSH with a key.

This error can also occur when trying to sync files and directories from remote machine to local system, if the rsync is not installed on the remote side.

rsync -zarvh [email protected]:/var/www/html/release /var/www/html/release
bash: rsync: command not found

Installing rsync on remote side will solve this case