Add chroot info

src/nixos/chroot.md

@@ -0,0 +1,19 @@
+# Entering nixos chroot from rescue
+
+```
+mount /dev/sda1 /mnt
+
+mount -o bind /dev /mnt/dev
+
+mount -o bind /proc /mnt/proc
+
+mount -o bind /sys /mnt/sys
+
+chroot /mnt /nix/var/nix/profiles/system/activate
+
+cp /etc/resolv.conf /mnt/etc/
+
+chroot /mnt /run/current-system/sw/bin/bash
+```
+
+Use `--option sandbox false` when `nixos-rebuild`