diff --git a/README.md b/README.md
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+++ b/README.md
@@ -13,6 +13,8 @@
 
  - [console.md](console.md): Using the host console
 
+ - [code-update.md](code-update.md): Updating OpenBMC and host platform firmware
+
 
 OpenBMC Development
 -------------------
diff --git a/code-update.md b/code-update.md
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@@ -0,0 +1,98 @@
+OpenBMC & Host Code Update
+===================
+
+After building OpenBMC, you will end up with a set of image files in
+`tmp/deploy/images/<platform>/`. The `image-*` symlinks correspond to components
+that can be updated on the BMC:
+
+ * `image-bmc` → `flash-<platform>-<timestamp>`
+
+    The whole-of-flash image for the BMC
+
+ * `image-initramfs` → `core-image-minimal-initramfs-palmetto.cpio.lzma.u-boot`
+
+    The small initramfs image; used for early init and flash management
+
+ * `image-kernel` → `cuImage`
+
+    The OpenBMC kernel cuImage (combined kernel and device tree)
+
+ * `image-rofs` → `obmc-phosphor-image-palmetto.squashfs-xz`
+
+    The read-only OpenBMC filesystem
+
+ * `image-rwfs` → `rwfs.jffs2`
+
+    The read-write filesystem for persistent changes to the OpenBMC filesystem
+
+ * `image-u-boot` → `u-boot.bin`
+
+    The OpenBMC bootloader
+
+Update from the OpenBMC shell
+-----------------------------
+
+To update from the OpenBMC shell, copy one or more of these `image-*` files to
+the directory:
+
+    /run/initramfs/
+
+(preserving the filename), then reboot. Before the system reboots, the new image
+will be copied to the appropriate flash partition.
+
+
+Update via REST
+---------------
+
+An OpenBMC system can download an update image from a TFTP server, and apply
+updates, controlled via REST. The general procedure is:
+
+ 1. Configure update settings
+ 2. Initiate update
+ 3. Check flash status
+
+### Configure update settings
+
+There are a few settings available to control the update process:
+
+ * `preserve_network_settings`: Preserve network settings, only needed if updating uboot
+ * `restore_application_defaults`: update read-only file system
+ * `update_kernel_and_apps_only`: update kernel and initramfs
+ * `clear_persistent_files`: Erase persistent files
+
+To configure the update settings, perform a REST PUT to
+`/control/flash/bmc/attr/<setting>`. For example:
+
+    curl -b cjar -k -H "Content-Type: application/json" -X PUT \
+        -d '{"data": 1}' \
+        https://bmc/org/openbmc/control/flash/bmc/attr/preserve_network_settings
+
+### Initiate update
+
+Perform a POST to invoke the `updateViaTftp` method of the `/flash/bmc` object:
+
+    curl -b cjar -k -H "Content-Type: application/json" -X POST \
+        -d '{"data": ["<TFTP server IP address>", "<filename>"]}' \
+        https://bmc/org/openbmc/control/flash/bmc/action/updateViaTftp
+
+### Check flash status
+
+You can query the progress of the flash with a simple GET request:
+
+    curl -b cjar -k https://bmc/org/openbmc/control/flash/bmc
+
+Host code update
+================
+
+Using a similar method, we can update the host firmware (or "BIOS"), by
+performing a POST request to call the `updateViaTftp` method of
+`/control/flash/bios` (instead of `/control/flash/bmc` used above). To initiate
+the update:
+
+    curl -b cjar -k -H "Content-Type: application/json" -X POST \
+        -d '{"data": ["<TFTP server IP address>", "<filename>"]}' \
+        https://bmc/org/openbmc/control/flash/bios/action/updateViaTftp
+
+And to check the flash status:
+
+    curl -b cjar -k https://bmc/org/openbmc/control/flash/bios