"connection refused" mounting with NFS3, when docker-alpine serves as NFS server

I am setting up an NFS server container, on Raspberry-PI. everything seems ok, including showmount, but when i do a straightforward mount, i get connection refused. forcing NFSv3 (mount -o nfsvers=3) succeeds. any insight?
Dockerfile:

```
FROM hypriot/rpi-alpine-scratch

MAINTAINER Ehud Kaldor

RUN apk update && \
apk add nfs-utils && \
rm -rf /var/cache/apk/*

EXPOSE 111/tcp 111/udp 2049/udp 34567 34568

#COPY nfs.conf /etc/conf.d/nfs
COPY entrypoint.sh /entrypoint.sh

CMD ["/entrypoint.sh"]
```

entrypoint.sh:

```
#!/bin/sh -eu

/usr/sbin/exportfs -r
/sbin/rpcbind --
/usr/sbin/rpc.nfsd -p 34567 |:
/usr/sbin/rpc.mountd -p 34568 -F
```

/etc/exports:

```
/my_exports *(ro,sync,no_subtree_check,insecure,fsid=0)
/my_exports/music *(rw,sync,no_root_squash,no_subtree_check,insecure,nohide)
```

run command (/mnt/sda1 is mounted with a directory that contains, amongst others, /music):

`docker run -it --rm -p 111:111/tcp -p 111:111/udp -p 2049:2049/tcp -p 34567:34567/tcp -p 34567:34567/udp -p 34568:34568/tcp -p 34568:34568/udp --privileged -v /mnt/sda1:/exports -v /root/docker/file-server/exports:/etc/exports --name file-server2 ehudkaldor/rpi-file-server:0.3
`

showmount:

```
> showmount -e AA.BB.CC.DD
Export list for AA.BB.CC.DD:
/my_exports/music *
/my_exports *
```

mount (defaults to nfs4):

```
> sudo mount -v AA.BB.CC.DD:/my_exports/music /mnt
mount.nfs: timeout set for Wed Sep 21 21:35:17 2016
mount.nfs: trying text-based options 'vers=4,addr=AA.BB.CC.DD,clientaddr=AA.BB.CC.EE'
mount.nfs: mount(2): Connection refused
mount.nfs: trying text-based options 'vers=4,addr=AA.BB.CC.DD,clientaddr=AA.BB.CC.EE'
mount.nfs: mount(2): Connection refused
mount.nfs: trying text-based options 'vers=4,addr=AA.BB.CC.DD,clientaddr=AA.BB.CC.EE'
mount.nfs: mount(2): Connection refused
```

forcing NFSv3:

```
> sudo mount -v -o nfsvers=3 -o nolock AA.BB.CC.DD:/my_exports /mnt
mount.nfs: timeout set for Wed Sep 21 21:37:00 2016
mount.nfs: trying text-based options 'nfsvers=3,nolock,addr=AA.BB.CC.DD'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying AA.BB.CC.DD prog 100003 vers 3 prot TCP port 34567
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying AA.BB.CC.DD prog 100005 vers 3 prot UDP port 34568
```

any insight?