field notes

Things that broke, and what fixed them.

Short write-ups from real work. Each one is a mechanism worth knowing, told without the specifics of where it happened.

• Headscale · Cloudflare Tunnel · DebuggingA green health check that proved nothingA Tailscale control server behind a tunnel passed every health check while no device could register.Read
• WireGuard · Tailscale · Linux routingTwo VPNs fighting over the same packetsWith a full-tunnel WireGuard VPN up, SSH over the tailnet timed out. The fix was one routing rule in the right place.Read
• SQLite · BackupsBacking up SQLite in WAL mode without losing writesCopying the database file of a busy SQLite database quietly drops recent changes. Use the database's own backup instead.Read
• Linux · Filesystems · UpdatesFlush before rename: updates that survive a power cutAn atomic rename is only atomic for the name. Without a flush, a power cut can leave a renamed file with the wrong contents.Read