diff --git a/build/Makefile b/build/Makefile
index 24626c0..9dcc5d8 100644
--- a/build/Makefile
+++ b/build/Makefile
@@ -37,8 +37,7 @@ hardware-shell:
 hardware-get:
 	docker cp upsilon-hardware:/home/user/upsilon/gateware/build/digilent_arty/gateware/digilent_arty.bit ../boot/
 	docker cp upsilon-hardware:/home/user/upsilon/gateware/arty.dtb ../boot/
-	docker cp upsilon-hardware:/home/user/upsilon/gateware/csr.json ../boot/
-	docker cp upsilon-hardware:/home/user/upsilon/gateware/csr_bitwidth.json ../boot/
+	docker cp upsilon-hardware:/home/user/upsilon/gateware/mmio.py ../boot/
 hardware-clean:
 	-docker container stop upsilon-hardware
 	-docker container rm upsilon-hardware
diff --git a/build/upsilon_key b/build/upsilon_key
new file mode 100644
index 0000000..46131a5
--- /dev/null
+++ b/build/upsilon_key
@@ -0,0 +1,38 @@
+-----BEGIN OPENSSH PRIVATE KEY-----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+-----END OPENSSH PRIVATE KEY-----
diff --git a/buildroot/board/litex_vexriscv/rootfs_overlay/root/.ssh/authorized_keys b/buildroot/board/litex_vexriscv/rootfs_overlay/root/.ssh/authorized_keys
new file mode 100644
index 0000000..679c0b3
--- /dev/null
+++ b/buildroot/board/litex_vexriscv/rootfs_overlay/root/.ssh/authorized_keys
@@ -0,0 +1 @@
+ssh-rsa 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 upsilon@root
diff --git a/doc/docker.md b/doc/docker.md
index 8f03444..b2fad68 100644
--- a/doc/docker.md
+++ b/doc/docker.md
@@ -94,9 +94,12 @@ Add the following to your SSH config:
 		HostName 192.168.1.50
 		StrictHostKeyChecking no
 		UserKnownHostsFile /dev/null
+		IdentityFile upsilon_key
 		User root
 		LogLevel QUIET
 
+Then copy the file `build/upsilon_key` to `$HOME/.ssh`.
+
 When the FPGA is connected you can access it with `ssh upsilon` (password
 `upsilon`).
 
diff --git a/gateware/Makefile b/gateware/Makefile
index 266bac2..faedd63 100644
--- a/gateware/Makefile
+++ b/gateware/Makefile
@@ -15,7 +15,7 @@ rtl_codegen:
 csr.json build/digilent_arty/digilent_arty.bit: soc.py
 	TFTP_SERVER_PORT=6969 python3 soc.py
 clean:
-	rm -rf build csr.json overlay.config overlay.dts pin_io.h arty.dts arty.dtb
+	rm -rf build csr.json arty.dts arty.dtb mmio.py
 	cd rtl && make clean
 test:
 	cd rtl && make test