Alpine Linux default gateway on different subnet

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As Alpine Linux uses busybox for a lot of its system tools it won’t set up the necessary routing if you have a default gateway on a non-local subnet to the IP. You want /etc/network/interfaces to look something like this:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address IP.ADDR.ADDR.ADDR
netmask 255.255.255.255   # or whatever is netmask
up route add DEFAULT.GW.IP dev eth0
up route add default gw DEFAULT.GW.IP

then run alpine-setup again

Testing Enterprise Infrastructure changes with brownouts

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Decommissioning or migrating services in enterprise environments will frequently reveal previously unknown dependencies which result in changes getting rolled back, wasting a lot of time.

To try and head these issues off you can test these changes with “brownouts”, shutting off the relevant infra temporarily (eg at a weekend) to expose any hidden dependencies.

When brownout testing, the following need to be borne in mind:

  • Dependencies may only be exposed for certain functions. Eg at startup, shutdown or other operations such as login. Thus a full test suit should be run and components restarted.
  • The effects of DNS, such as caching.
  • Regional differences.