SG-1100 is a decent firewall for a home setup, It uses PFSense as its core and has 1 Gbps throughput. The only problem is that if it loses power for any reason like power outage or getting unplugged, it sometimes goes into a boot loop because of filesystem gets corrupted. You definitely don’t want this to happen to a production firewall.

The fix is easy though.

1- Connect to the device using the serial console: sudo screen /dev/ttyUSB0 115200 or if you’re on a MAC:
sudo screen /dev/cu.usbserial 115200.

2- Power cycle the device so it starts to boot from beginning, then watch for when this prompt comes up, press any key except Enter to interrupt:

3- type boot -s and hit Enter, this will boot the device into Single User Mode

4- At the next prompt, simply hit Enter to get a shell:

5- Run fsck -y /, this will fix the whole filesystem and won’t take long. You may need to run this command a few times, I don’t exactly know why, but it seems it doesn’t fix everything in one go, I ran it 5 times, and the first 3 times it was making changes and fixing stuff, nothing was done on the last 2 times though.

6- Type reboot and Enter

Your device should be booting normally now.