I’ve been setting up a Lenvo tiny system, which came with an M.2 wifi card. I’m going to probably replace it with another Intel GB / 2.5 GB adapter at some point, but right now I don’t really have a reason to. It is always a little scary when you make major changes to your network configuration on a headless system. This box isn’t physically far away, but it is indeed tucked away in another part of the house and I have no desire to bring a monitor over to it.
I realized, the wifi could serve a purpose in case I bork the bridge config somehow, or something unexpected breaks my configuration. Because I used wifi for the Debian netinstall, ifupdown already connects to wifi on boot, so there’s my failsafe. However, I don’t want or need that to stay up after the wired network is up. So I came up with this:
@reboot sleep 60 && ping -c 3 -I br0 10.0.0.1 >/dev/null 2>&1 && ifdown wlp2s0
Put this in root’s crontab, 60 seconds after cron starts it will try to ping something on the LAN, trying three times. If it can ping successfully, we bring down our backup interface. Beautiful.
This would make even more sense with a cheap USB network adapter just to have a failsafe if you’re experimenting and don’t want to lock yourself out of a system without a monitor (or even a physical serial port, for that matter).
Fail-safe, for what? – long version, for those so-inclined
Well, I wanted to be able to easily network some VMs on this thing, so I set up bridged networking. For those who don’t know, this is how Proxmox lets your VMs basically all share a NIC and each get a DHCP lease from your main network, no double-NAT nonsense, and no need to configure static routes either. I briefly did try ProxMox on this thing, and not to talk down of it but there is a reason I don’t use it… has way too much going on out of the box that I’ll never use. It is a great product, and it definitely has its place but I like the minimal-manual style of setting things up. If I wanted to take advantage of the cluster / high availability features or ZFS snapshots then it is a great way to save you a ton of hassle manually setting up some pretty complicated stuff… But I’m not doing anything that fancy. Proxmox IMO is overkill if you just need to run a few VMs, jails or containers. It is convenient as a “poor man’s KVM” though.
The OpenWRT project is a completely free and open source linux system intended to replace the firmware on your router / wireless AP. It has tons of packages available and has a very active community and development scene. I’ve used it for years, it is incredibly good firmware. If you’ve never heard of it think DD-WRT but better, in my opinion.