TimeShift is a “Linux Equivalent” to Apple TimeMachine, but it uses hard links and rsync to perform its task.

This means that a regular NAS drive cannot be used, as hard links are not something you can do with a network protocol.

However, as I use a Synology drive, I can share a LUN to the Linux machine using iscsi

Using SAN Manager on Synology DSM.

(SAN = Storage Area Network)

Create a LUN

Create an ISCSI target

Now on your Linux box (this one is Ubuntu)

Edit ISCSI config

# vi /etc/iscsi/initiatorname.iscsi

## DO NOT EDIT OR REMOVE THIS FILE!
## If you remove this file, the iSCSI daemon will not start.
## If you change the InitiatorName, existing access control lists
## may reject this initiator. The InitiatorName must be unique
## for each iSCSI initiator. Do NOT duplicate iSCSI InitiatorNames.
#InitiatorName=iqn.2004-10.com.ubuntu:01:e3d5122630f5
InitiatorName=iqn.2000-01.com.synology:synology.default-target.372f9449427

# vi /etc/iscsi/iscsid.conf, make the following changes

##node.leading_login = No
node.leading_login = Yes

node.session.auth.username_in = <username>
node.session.auth.password_in = <password>

Restart the ISCSI service

# systemctl restart iscsi.service

Start up script

root@Ubuntu-iMac:~# cat /usr/local/sbin/start-iscsi 
#!/bin/bash

iscsiadm -m discovery -t sendtargets -p <nas drive ip>
# iscsiadm -m node -o show
iscsiadm -m node --login

now run the startup-script with sudo before running timeshift!