Secondo me meglio che viene salvata localmente, sarebbe più comodo poi.
la cartella è la /root ....
basta inserire il la gui lì e fare l'aggiornamento e si autoapplica...
ora la procedura di sysupgrade è così
root@modemtim:/# sysupgrade /tmp/AGTEF_1.0.2_CLOSED.rbi
Saving config files...
Closing voice...
stopped process in pidfile '/var/run/led-fw-interface.lua.pid' (pid 66 33)
Sending TERM to remaining processes ... status-led-even ledfw.lua logd swmdk bcmubusbridge netifd conntrackd wansensing.lua cupsd dhcpopassthrud lua ubusd dnsmasq dhcpsnooper mcsnooper neighmd smbd smbd nmbd mobiled igmpproxy mldproxy mountd lte-doctor-logg lua crond nginx nginx cwmpd lua ntpd cgrulesengd
Sending KILL to remaining processes ... lua
Switching to ramdisk...
open: No such file or directory
Performing system upgrade...
Copying root file to ram...
Root file preserved!
GUI File found! Good Job!
Restoring GUI file in ram
Device Rooted
Programming...
ash: lua: not found
Unlocking bank_1 ...
Writing from <stdin> to bank_1 ... [w]ash: ubus: not found
Clearing FVP of /dev/mtd3...
Firmware upgrade done
Upgrade completed
Rebooting system...
(esclusi quei due errori che sono trascurabili... funziona )