Well, These are the steps I've followed to run jdownlodaer into my ds1812+, please understand my poor english
** Install bootstap: just follow these steps from
viewtopic.php?f=77&t=487801: If you havent enabled ssh earlier, do so in «ControlPanel--->Terminal» and check «Enable SSH service»
2: Connect to youre NAS over SSH (terminal in mac/linux or Putty for Windows) as «root». The password is the same as for «admin»
3: Change to the folder «/volume1/»
4: Download the bootstrap for intel based NAS by typing:
«wget
http://ipkg.nslu2-linux.org/feeds/optwa ... 7_i686.xsh»
5: Make the file runable by typing «chmod +x syno-i686-bootstrap_1.2-7_i686.xsh
6: Run it: «sh syno-i686-bootstrap_1.2-7_i686.xsh»
7: Then its finished, change to / by typing «cd /» and then make an symlink by typing «ln -s /volume1/@optware /opt»
8: Use the «vi» editor to edit the file «/etc/profile» («vi /etc/profile») and check that «PATH=/opt/bin:/opt/sbin:$PATH» is in the file. If not, add it to the end of the file. Save and quit «vi»
9: Use «vi» again to edit the file «/root/.profile» («vi /root/.profile») and add and # on the following lines:
#PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/syno/sbin:/usr/syno/bin:/usr/local/sbin:/usr/local/bin
#export PATH
10: Reboot youre NAS by typing «reboot»
11: After the NAS have started, ssh to it again.
**
Install chroot debian: You need one debian virtual machine to create the chroot environment, commands with VM prefix belong to Virtual Machine, commands with SN belong to SyNology and commands with DB belong to debian:
1.- Create the folders for the environment:
VM$ mkdir -p /var/tmp/chroottarget
SN$ mkdir -p /volume1/debian
2.- Download bootstrap and install it:
VM$ wget
http://ftp.es.debian.org/debian/pool/ma ... 42_all.deb VM$ dpkg -i debootstrap_1.0.42_all.deb
3.- Download debian environment:
VM$ debootstrap --foreign --arch amd64 squeezey chroottarget "http://ftp.es.debian.org/debian"
4.- Compress it and copy into your synology:
VM$ tar -czf chroottarget.tar.gz chroottarget
5.- Uncompress it:
SN$ tar -xzf chroottarget.tar.gz
6.- Configure it:
SN$ cp /etc/resolv.conf /volume1/debian/etc
SN$ echo `hostname` > /volume1/debian/etc/hostname
SN$ mount -o bind /proc /volume1/debian/proc
7.- Jump into the jail

SN$ chroot debian /bin/bash
SN$ echo "deb
ftp://ftp.es.debian.org/debian stable main contrib non-free" > /etc/apt/sources.list
SN$ apt-get update
**
Install VNC and JDownloader1.- Install and configure VNC server:
DB$ apt-get install vnc4server
DB$ vnc4server
2.- Install java:
DB$ apt-get install openjdk-6-jre
3.- Download and run jdownloader:
DB$ wget
http://installer.jdownloader.org/jd_unix_0_9.sh DB$ chmod +x jd_unix_0_9.sh
DB$ ./jd_unix_0_9.sh
4.- Access to jdowloader via vnc client and activate web mode (if you want...)
5.- Enjoy!!!!