Firmware

According to https://wiki.mikrotik.com/wiki/SwOS/RB250_RB260#Summary

new RB260GS (CSS106-5G-1S), new RB260GSP(CSS106-1G-4P-1S) supports SwOS v2.0 and newer.

Probably not correct urls for our CSS106-5G-1S:

https://download2.mikrotik.com/swos2/css106/swos-css1061g4p1s-2.0.bin
https://download2.mikrotik.com/swos2/css106/swos-css1061g4p1s-2.2.bin

version

from web interface

Firmware
Current Installed Version	2.7 (built at Fri Dec 15 2017 09:42:48 GMT+0100 (CET))
Latest Available Version	2.7 (built at Fri Dec 15 2017 09:42:48 GMT+0100 (CET))

Linux setup

dpavlin@x230:~$ sudo ifconfig enp0s25 192.168.88.1