C:\WINDOWS\system32\config\systemprofile\AppData\Local\
is frequently cleared for almost any reason: Windows updates,
System Restore, even various System Cleaner utilities.
The server-state.conf file in AppData\Local could be deleted
at any time, which would break login until the node is removed
from the Admin Panel allowing it to create a new key.
Carefully copy any AppData state to ProgramData at startup.
If copying the state fails, continue to use AppData so at
least there will be connectivity. If there is no state,
use ProgramData.
We also migrate the log.conf file. Very old versions of
Tailscale named the EXE tailscale-ipn, so the log conf was
tailscale-ipn.log.conf and more recent versions preserved
this filename and cmdName in logs. In this migration we
always update the filename to
c:\ProgramData\Tailscale\tailscaled.log.conf
Updates https://github.com/tailscale/tailscale/issues/2856
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
It's still Windows-only for now but it's easy to de-Windows-ify when needed.
Moving it out of corp repo and into tailscale/tailscale so we can use
it in ipnserver.BabysitProc.
Updates #726
