The engine

The engine is where your containers really run: a small Linux machine with Docker inside. DoCatz sets it up, starts it, stops it and keeps it in one folder. Open it with Engine in the rail (mod+6).

The Engine page

At the top you see the engine’s state, and when it runs, the Docker version, CPUs and memory.

While the engine starts, each step shows with a tick when it is done:

When DoCatz’s own command-line tools are not there yet, one more step follows: Install docker, compose and buildx.

If a step fails, the error shows with an Engine log button. The log has Copy, which is handy for a bug report.

Start, stop and quit

• Start with DoCatz (on by default) — Starts the engine when DoCatz opens. It is in the Resources card.
• Closing the window keeps DoCatz, and the engine, running in the menu barsystem tray. The tray menu can start and stop the engine too.
• Engine → Start / Stop / Restart in the menu do the same as the buttons; Refresh (mod+R) reads the container list again.

Resources

[wsl2]
memory=6GB
processors=4

Docker command line

This card decides how the docker in your terminals reaches DoCatz. Nothing here changes on its own.

• Use DoCatz as the default — Makes the docatz context the current one, so docker in any terminal talks to DoCatz. The card shows the current context (Now: …). Without it, use docker --context docatz …. DoCatz creates the docatz context on every start, but only this switch makes it the current one (it writes currentContext in ~/.docker/config.json). Turn it off to go back to the context you had.
• docker, compose and buildx — where DoCatz’s own CLIs are (Docker CLI 29.9.2 in …), or Not installed yet — the first engine start installs them. with Install. When DoCatz finds another docker on this computer, it adds Your own docker (…) keeps working.
• Add to PATH — new terminals find DoCatz’s docker, docker-compose and docker-buildx first: DoCatz writes a marked block (# >>> DoCatz >>>) to ~/.zprofile, and to ~/.bash_profile when you have one.through your user Path variable. If you keep your own docker, you can leave it off — the context is enough.
• DOCKER_HOST — the engine’s address, with Copy (it copies an export DOCKER_HOST=… line): unix://~/.docatz/run/docker.socknpipe:////./pipe/docatz_engine. Useful for tools that read DOCKER_HOST instead of contexts.

DoCatz’s compose is a docker CLI plugin (in ~/.docatz/cli-plugins, registered in ~/.docker/config.json), so docker compose works, and it is also there as a standalone docker-compose.

The Commands page has these as ready-made lines, such as docker context use docatz.

Bundled versions

Everything the engine needs is downloaded by DoCatz itself, at a fixed version:

Every download is pinned by its SHA-256. If a file does not match, nothing is installed and you see <file> did not match its checksum — the download was damaged or changed, nothing was installed. Start again to download it anew. Inside the VM, the first start installs Docker from get.docker.com.

Disk usage

Disk usage lists Images, Containers, Volumes and Build cache, each with its Count, Size and what Can be freed. Clean up… on a row shows exactly what would go before anything is removed — see Clean up.

Move from another Docker

Already have images and volumes in another Docker engine on this computer? DoCatz can copy them across, so you do not start from zero. Once DoCatz’s engine runs, the Engine page looks for Docker Desktop, OrbStack, Colima and Rancher Desktop (on Windows: Docker Desktop and Rancher Desktop). When it finds one, the card Move from another Docker lists it — Copy images and volumes onto DoCatz’s engine. The other one keeps them, so both can stay side by side.

• A running one shows Running · Docker <version> and Choose what to move….
• One that is installed but stopped says Installed, not running — start it to move from it, with Look again.

Choose what to move… opens Move from <name>: Copies onto DoCatz’s engine. <name> keeps everything, so both can stay side by side; each has its own docker context. It lists:

• Images — every tagged image, with its size.
• Volumes — every named volume, with its size and how many of its containers use it. Anonymous volumes are left out.

Everything is ticked except what DoCatz already has, which wears an in DoCatz badge (a volume of the same name in DoCatz gets the files added to it). All and None tick or clear a list, and the footer counts what you picked and its size. When a picked volume is still in use, the dialog warns you to stop its containers in the other engine first, as a database still writing can be copied half way.

Move copies the picked items one at a time, each a step with its progress (catz-shop-db · 120 MB of 480 MB):

• an image goes across as it is (docker save from the other engine into docker load on DoCatz’s);
• a volume is made again on DoCatz with the same name and labels, so docker compose finds it as its project’s own, and its files are copied with tar through a small alpine:3.20 container on each side (pulled first when an engine does not have it).

Cancel stops the move. An item that fails does not stop the rest; at the end the dialog lists what could not be moved. Nothing is removed from the other engine, and your terminal’s docker keeps using whichever context it used before — see Docker command line.

Details

• VM — the VM manager, the Linux kernel and the architecture.
• Folder — where the VM lives; click it to open it in FinderFile Explorer.
• macOSWindows — your computer’s CPUs, memory and architecture.

Engine log is here too, even when nothing failed.

Reset the engine

Deletes the VM and its disk: every container, image and volume in DoCatz. Project folders on this MacPC are not touched.

Reset… asks Reset the engine?; type reset to go ahead. The next start sets the engine up fresh. Anything that lives only inside a volume is gone, so copy it out first if you need it (the Files tab can save a folder as a .tar).

Where the engine keeps its files

Everything the engine downloads and runs lives in one folder: ~/.docatz%USERPROFILE%\.docatz.

DoCatz’s settings, certificates and project .env files live in its app data folder instead — see Where your data lives.

Install WSL (Windows)

Last updated 2026-11-03