The debian repository has been taken offline
see bye, bye Debian and yum repos
you now need to install the debian package manually.

Modify /etc/apt/sources.list:

deb http://debian.slimdevices.com stable main

Install Squeezebox Server:

apt-get update
apt-get install logitechmediaserver

Manual:

sudo service logitechmediaserver stop
// download the package, link see below
dpkg -i <package>
sudo service logitechmediaserver start

download Debian Package for instructions, see Debian Package

• reboot server
• upgrade your clients firmware
• join user squeezeboxserver to group of music files

adduser squeezeboxserver <musicgroup> # or
usermod -a -G <musicgroup> <user>

• modify access rights for squeezeboxserver user (do this on the server where the music files physically reside)

chown -R <user>:<musicgroup> /music # or
chgrp -R <musicgroup> /music # faster

1. If you want to access the music directory and contents from different machines or VMs, choose users (gid=100) as <musicgroup>, then add user squeezeboxserver to users. This is also the group you can access the music directories from Media Server Installation - Synology DSM 4.3 (Oberon)
2. New music files from a Windows client will be written to the server with 755 directory and 644 file permissions
3. To make the music directory accessible for the client, either leave the 644 file permissions or change group to <musicgroup> and change 750 directory and 640 file permissions
4. You can use the following commands to do this throughout the music tree:

find /path/to/music/dir -type d -exec chmod 750 {} + # directories
find /path/to/music/dir -type f -exec chmod 644 {} + # files