diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec5dc2f..440d321 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 |Version|Date|Notes|
 |---|---|---|
+|   |2021-03-17|Add RAM=max and RAM=half to dynamically select ram at runtime (DEFAULT).|
 |   |2021-03-06|Change envs to require --envs. Automatically enable --envs if --output-env is used. Same for plists, bootdisks. Fix help ugliness and sanity of generate serial scripts. Fix bootdisk not getting written to persistent file when using NOPICKER=true. NOPICKER=true is overridden by a custom plist now anyway. Remove useless case statements. Allow -e HEADLESS=true as human readable alternative to -e DISPLAY=:99.|
 |4.1|2021-03-04|Add `-e MASTER_PLIST_URL` to all images to allow using your own remote plist.|
 |   |2021-03-03|Add `WIDTH` and `HEIGHT` to set the x and y resolutions, use in conjuction with serial numbers.|
diff --git a/Dockerfile b/Dockerfile
index 7f0f242..0ab8338 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -207,12 +207,19 @@ RUN git clone --recurse-submodules --depth 1 --branch "${BRANCH}" "${REPO}"
 # for example, -e ADDITIONAL_PORTS=hostfwd=tcp::23-:23,
 ENV ADDITIONAL_PORTS=
 
+# dynamic RAM options for runtime
+ENV RAM=max
+# ENV RAM=half
+
 RUN touch Launch.sh \
     && chmod +x ./Launch.sh \
     && tee -a Launch.sh <<< '#!/bin/sh' \
     && tee -a Launch.sh <<< 'set -eu' \
     && tee -a Launch.sh <<< 'sudo chown    $(id -u):$(id -g) /dev/kvm 2>/dev/null || true' \
     && tee -a Launch.sh <<< 'sudo chown -R $(id -u):$(id -g) /dev/snd 2>/dev/null || true' \
+    && tee -a Launch.sh <<< '[[ "${RAM}" = max ]] && export RAM="$(("$(head -n1 /proc/meminfo | tr -dc "[:digit:]") / 1000000"))"' \
+    && tee -a Launch.sh <<< '[[ "${RAM}" = half ]] && export RAM="$(("$(head -n1 /proc/meminfo | tr -dc "[:digit:]") / 2000000"))"' \
+    && tee -a Launch.sh <<< 'sudo chown -R $(id -u):$(id -g) /dev/snd 2>/dev/null || true' \
     && tee -a Launch.sh <<< 'exec qemu-system-x86_64 -m ${RAM:-2}000 \' \
     && tee -a Launch.sh <<< '-cpu Penryn,vendor=GenuineIntel,+invtsc,vmware-cpuid-freq=on,+pcid,+ssse3,+sse4.2,+popcnt,+avx,+aes,+xsave,+xsaveopt,check \' \
     && tee -a Launch.sh <<< '-machine q35,accel=kvm:tcg \' \
diff --git a/README.md b/README.md
index 2d5344f..d7746c5 100644
--- a/README.md
+++ b/README.md
@@ -182,9 +182,12 @@ docker start -i containerid
 
 This is my favourite container. You can supply an existing disk image as a docker command line argument.
 
+Pull images out using `sudo find /var/lib/docker -size +10G | grep mac_hdd_ng.img` 
+
 Supply your own local image with `-v "${PWD}/mac_hdd_ng.img:/image"` and use `sickcodes/docker-osx:naked`
 
-- Naked image is for booting any existing .img file.
+- Naked image is for booting any existing .img file, e.g in the current working directory (`$PWD`)
+
 - By default, this image has a variable called `NOPICKER` which is `"true"`. This skips the disk selection menu. Use `-e NOPICKER=false` or any other string than the word `true` to enter the boot menu. This lets you use other disks instead of skipping the boot menu, e.g. recovery disk or disk utility.
 
 ```bash
@@ -298,7 +301,6 @@ docker run -it \
 docker run -it \
     --device /dev/kvm \
     --device /dev/snd \
-    -e RAM=4 \
     -p 50922:10022 \
     -v /tmp/.X11-unix:/tmp/.X11-unix \
     -e "DISPLAY=${DISPLAY:-:0.0}" \