I tried resizing partitions so upgrades are easier, but ran into “telnet connection timed out”. I found a solution on tjc so I’m reposting here for archive purposes.
The relevant part is:
connecting to your device in recovery mode
older Linux (e.g. Debian Jessie):
typing ifconfig -a should list a new device usb0 (or a greater number, if you had other usb devices before)
configure this device with: dhclient usb0
new Linux (e.g. Debian Stretch):
typing ip address list should list a new device without ip-address. In my case: enp0s20u1
configure this device with: dhclient enp0s20u1
type telnet 10.42.66.66 to connect to your SailfishX device
You should now see:
Jolla Recovery v2.0
Welcome to the recovery tool!
The available options are:
Reset device to factory state
Reboot device
Shell
Perform file system check
Run sshd
Exit
Type the number of the desired action and press [Enter]:
typing ifconfig -a should list a new device usb0 (or a greater number, if you had other usb devices before)
configure this device with: dhclient usb0
new Linux (e.g. Debian Stretch):
typing ip address list should list a new device without ip-address. In my case: enp0s20u1
configure this device with: dhclient enp0s20u1
type telnet 10.42.66.66 to connect to your SailfishX device
You should now see:
-----------------------------
Jolla Recovery v2.0
-----------------------------
Welcome to the recovery tool!
The available options are:
1) Reset device to factory state
2) Reboot device
3) Shell
4) Perform file system check
5) Run sshd
6) Exit
Type the number of the desired action and press [Enter]:
You can select option 3 to get a shell on your SailfishX device.
(!) Please be careful about what you are doing and respect the warranty warning!
Hint: “devicelock code” is the code you have to enter to unlock your device in normal operation mode (after your display was off for 10 minutes or longer).