mention ipv6-only targets workaround

Author: Mic92

docs/SUMMARY.md

@@ -21,5 +21,6 @@ Refer to the following documentation for more information.
 - [Use without flakes](./howtos/use-without-flakes.md)
 - [Terraform](./howtos/terraform.md)
 - [Nix-channels / `NIX_PATH`](./howtos/nix-path.md)
+- [IPv6-only targets](./howtos/ipv6.md)
 
 [Reference](./reference.md): Reference Guide

docs/howtos/INDEX.md

@@ -19,3 +19,5 @@
 [Terraform](./terraform.md)
 
 [Nix-channels / `NIX_PATH`](./nix-path.md)
+
+[IPv6-only targets](./ipv6.md)

docs/howtos/ipv6.md

@@ -0,0 +1,23 @@
+# NixOS-anywhere on Ipv6-only targets
+
+As GitHub engineers still haven't enabled the ipv6 switch, the kexec image
+hosted on GitHub, cannot be used unfortunally on ipv6-only hosts. However it is
+possible to use an ipv6 proxy for github content like that:
+
+```
+nixos-anywhere \
+  --kexec https://gh-v6.com/nix-community/nixos-images/releases/download/nixos-unstable/nixos-kexec-installer-noninteractive-x86_64-linux.tar.gz \
+...
+```
+
+This proxy is hosted by (numtide)[https://numtide.com/]. It also works for ipv4.
+
+Alternativly it is also possible to reference a local file:
+
+```
+nixos-anywhere \
+  --kexec ./nixos-kexec-installer-noninteractive-x86_64-linux.tar.gz \
+...
+```
+
+This tarball will be than uploaded via sftp to the target.