Question: I'm logged in to my Synology NAS and although I can rsync from my servers to the NAS and vice versa, I can't use rsync where the source and destination are both on the DiskStation.

```
midnight my_user /tmp> rsync -Pauvvv synoproxy.conf del.del
sending incremental file list
[sender] make_file(synoproxy.conf,*,0)
send_file_list done
send_files starting
server_recv(2) starting pid=15513
ERROR: module is read only
rsync error: syntax or usage error (code 1) at main.c(1034) [Receiver=3.0.8]
[Receiver] _exit_cleanup(code=1, file=main.c, line=1034): about to call exit(1)
rsync error: rsync service is no running (code 43) at io.c(653) [sender=3.0.8]
[sender] _exit_cleanup(code=43, file=io.c, line=653): about to call exit(43)
midnight my_user /tmp> 

```

I don't know why I'm having module issues with the syntax I've provided. Why is this producing an error?

Answer: 
It appears one has to use absolute directory like /volume1/homes/username/...
Reviving this thread, I stumbled upon the same issue with a more recent version of a synology NAS. It appears synology runs an rsync daemon, so the syntax isn't the same as for regular paths.

First you can 

```
nmap -p 873 --script rsync-list-modules <NAS_IP>

```

to get a list of your rsync modules that the rsync daemon knows about. As far as I understood, the names are those of the root folders in your NAS.

Then instead of 

```
rsync /path/to/src user@IP:/path/to/dst

```

Use 

```
rsync /path/to/src user@IP::modulename/path/in/module

```

There can also be permission issues, but I think that's at least one part of the issue.