Install netatalk (afp) in Ubuntu with service announcing and provide a Time Machine share. Users must belong to `timemachine` group to be allowed to use it.

afp.conf

[TimeMachine]
    path = /store/time-machine
    time machine = yes
    valid users = @timemachine

install.sh

#!/bin/bash
# This script will install the latest stable version of netatalk 3.x and libevent in order
# to configure a Time machine volume

# Versions to use
libevent_version="2.0.22-stable"
netatalk_version="3-1-7"

# Install prerequisites:
apt-get install build-essential pkg-config checkinstall git avahi-daemon libavahi-client-dev libcrack2-dev libwrap0-dev autotools-dev automake libtool libdb-dev libacl1-dev libdb5.3-dev db-util db5.3-util libgcrypt11 libgcrypt11-dev libtdb-dev

# libevent
cd /usr/local/src
wget http://skylink.dl.sourceforge.net/project/levent/libevent/libevent-2.0/libevent-${libevent_version}.tar.gz
tar xfv libevent-${libevent_version}.tar.gz
cd libevent-${libevent_version}
./configure
make
checkinstall \
    --pkgname=libevent-${libevent_version} \
    --pkgversion=${libevent_version} \
    --backup=no \
    --deldoc=yes \
    --default --fstrans=no
cd ../

# netatalk
git clone git://git.code.sf.net/p/netatalk/code netatalk-code
cd netatalk-code
git checkout netatalk-${netatalk_version}
./bootstrap
./configure \
    --enable-debian \
    --enable-krbV-uam \
    --enable-zeroconf \
    --enable-krbV-uam \
    --enable-tcp-wrappers \
    --with-cracklib \
    --with-acls \
    --with-dbus-sysconf-dir=/etc/dbus-1/system.d \
    --with-init-style=debian-sysv \
    --with-pam-confdir=/etc/pam.d \
    --with-tracker-pkgconfig-version=0.16
make
checkinstall \
    --pkgname=netatalk \
    --pkgversion=${netatalk_version} \
    --backup=no \
    --deldoc=yes \
    --default \
    --fstrans=no

# Install time machine configuration
cp afp.conf /usr/local/etc/

# Start services
service avahi-daemon start
service netatalk start

# Instruct User
echo "************************************"
echo "*     INSTALLATION COMPLETE        *"
echo "************************************"
echo " To add users to your Time Machine symply"
echo " simadd them to the timemachine group by"
echo " running the following command as root:"
echo "     sudo usermod -a -G timemachine <username>"
echo " Afterwards they can log in the Time Machine"
echo " volume with their linux user and password"
echo "------------------------------------"
echo " CONFIG FILE: /usr/local/etc/afp.conf"