iso: document iso cache / closures (speed!)

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David Arnold 2021-03-16 18:01:29 -05:00
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@ -46,6 +46,18 @@ _Note: the [static link-local IPv6 address][staticLLA] and [MulticastDNS][mDNS]
configured on the live installer. If you wish to enable [MulticastDNS][mDNS]
for your environment, you ought to configure that in a regular [profile](../../profiles)._
## ISO image nix store & cache
The iso image holds the store to the live environment and _also_ acts as a binay cache
to the installer. To considerably speed up things, the image already includes all flake
`inputs` as well as the `devshell` closures.
While you _could_ provision any machine with a single stick, a bespoke iso maximises
those local cache hits.
For hosts that don't differ too much, a common usb stick might be ok, whereas when
there are bigger differences, a bespoke usb stick will be considerably faster.
## EUI-64 LLA & Host Identity
The iso's IPv6 Link Local Address (LLA) is configured with a static 64-bit Extended
@ -97,11 +109,6 @@ $ flk install NixOS --impure # use same host as above
<!-- TODO: find out why --impure is necesary / PRs welcome! -->
_Note: You _could_ install another machine than the one your iso was built for,
but the iso doesn't carry all the necesary build artifacts so the target would
start to build the missing parts on demand instead of substituting them from
the iso itself._
[manual]: https://nixos.org/manual/nixos/stable/index.html#sec-installation-partitioning
[mDNS]: https://en.wikipedia.org/wiki/Multicast_DNS
[NDP]: https://en.wikipedia.org/wiki/Neighbor_Discovery_Protocol