I have Kubuntu 18.10 and have downloaded and successfully run KDE Neon in a container using the neondocker ruby script. But I'm new to Docker and containers, and I can't figure out how, if I change or add packages to the running neon docker container, how I commit and restart the modified Neon image. Can someone give me or point me to the commands to do this? Or ..... since the neondocker ruby script provides only choices to download/run dev-stable, dev-unstable, etc versions, is there a modified version to run a previously committed modified image (or how would I modify the ruby script to do that)?

Also, if I start the Neon container using the neondocker ruby script with no options I get a container with a black screen, whereas if I use the Wayland option I get the working Neon Docker container. Is Wayland a requirement to run the Neon container on Kubuntu 18.10, or am I missing something?

Thx, Gus

Nobody responded to my question and I finally figured out a way to do it, so I thought I'd post my solution for comments, if any, and in case it might help someone else. I note this is for Kubuntu 18.10 with KDE and Plasma, and my system has Intel graphics and driver, where the video device is /dev/dri. For some reason the docker run command needs the --device /dev/dri option twice, not sure why.

{... download kdeneon/plasma:dev-stable, and ..... create a local repository and put it there}

docker pull kdeneon/plasma:dev-stable
docker image tag kdeneon/plasma:dev-stable localhost:5000/randysneon022419

{the initial version in the local repository is TAGged :latest by default. I then made a couple revisions TAGging them :1, :2, :3 and 4:}
{... and to run my modified TAG 4 version of kdeneon}

$ docker run -d --rm -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=:0 --device /dev/dri --device /dev/dri --expose 5000 --cap-add ALL localhost:5000/randysneon022419:4 startplasmacompositor

d908d3691e252890fe4bdffe9834f01cc66ac1b1ac21353bfdd458556a537597

{... I make further changes to TAG 4 .... and then commit to TAG 5}

$ docker commit d908d3691e252890fe4bdffe9834f01cc66ac1b1ac21353bfdd458556a537597 localhost:5000/randysneon022419:5

sha256:4033a0e697e58a496bf69c97f84ac507ecd8a61e00868c8f57e5233a8c1a6341

{then ....}

$ docker images

REPOSITORY TAG IMAGE ID CREATED SIZE
localhost:5000/randysneon022419 5 4033a0e697e5 25 seconds ago 3.79GB
localhost:5000/randysneon022419 4 e8bf9104f3ea 13 hours ago 3.16GB

{... run TAG 5}

$ docker run -d --rm -v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=:0 --device /dev/dri --device /dev/dri --expose 5000 --cap-add ALL localhost:5000/randysneon022419:5 startplasmacompositor

01521828fc5586ceabe3a3d4f894466dc5601837895765f3e83c6453b505b94b

{... and the committed changes show up when I run TAG 5}