[6] If you get no errors starting up the service or anything, you're good! For good measure, you could send yourself some sats from a mobile wallet, restart the service with sudo service lightningd restart and even restore the node from the backup, then check if everything's fine.
Question:
1. Is restoring the lightning node from the same device or even an entirely different device going to cause my existing channels to close forcibly?
No, that's the idea of the backups. While your old / broken node is offline, the channel will just be offline. The counterparty could force-close, if they don't believe you're going to come back online, though.
If they don't, all the channels should be back just as they were before.
2. How to restore a c-lightning node? Do i simply remove the hsm_secret file and that is called a restore?
Thanks guys.
As the guide says:
To recover, simply get all the backup database files. Note that SQLITE3 will sometimes create a -journal or -wal file, which is necessary to ensure correct recovery of the backup; you need to copy those too, with corresponding renames if you use a different filename for the backup database, e.g. if you named the backup backup.sqlite3 and when you recover you find backup.sqlite3 and backup.sqlite3-journal files, you rename backup.sqlite3 to lightningd.sqlite3 and backup.sqlite3-journal to lightningd.sqlite3-journal. Note that the -journal or -wal file may or may not exist, but if they do, you must recover them as well (there can be an -shm file as well in WAL mode, but it is unnecessary; it is only used by SQLITE3 as a hack for portable shared memory, and contains no useful data; SQLITE3 will ignore its contents always). It is recommended that you use the same filename for both main and backup databases (just on different directories), and put the backup in its own directory, so that you can just recover all the files in that directory without worrying about missing any needed files or correctly renaming.