diff --git a/README.md b/README.md
index 17a9ac3..1b55a70 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,26 @@
 # NixOS Hypervisor config
 
 NixOS Flake to deploy an hypervisor with microvm capability and microvms config
+
+Build an image :
+
+```
+# generate a proxmox VMA file
+nixos-generate -f proxmox --flake .#nixos-hypervisor
+
+# generate a qcow2 file for plain KVM
+nixos-generate -f qcow --flake .#nixos-hypervisor
+```
+
+Rebuild the config for an existing VM :
+
+```
+# build locally
+cd /etc/nixos/
+git clone https://git.le43.eu/tbarnouin/nixos-hypervisor.git
+cd nixos-hypervisor
+sudo nixos-rebuild switch
+
+# build remotely
+nixos-rebuild --target-host root@<IP> switch --flake .#nixos-hypervisor
+```