Companion packages¶

A companion package is a Debian package named mcprack-mcp-server-<name> built from the same source as mcp-server-<name>. It ships no files. Its maintainer scripts talk to mcprack:

postinst

Registers the server in the local catalog, as the mcprack user:

mcprack server create mcp-server-<name> \
    --label '<Label>' \
    --transport stdio \
    --command /usr/bin/mcp-server-<name> \
    --category debian \
    --enabled

prerm (on remove and deconfigure)

Unregisters it:

mcprack server delete mcp-server-<name> --yes

Both do nothing — successfully — when mcprack is not installed on the host, so a companion never blocks an installation or a removal on a machine that does not run mcprack.

Dependencies¶

Depends: mcprack (>= 1.6.0), mcp-server-<name> (= ${binary:Version})

The exact-version dependency makes apt install and upgrade the pair together. All companions in this documentation require mcprack 1.6.0 or newer and share their version with the server.

What you get, and what you still do¶

Automatic	Manual
A catalog entry named `mcp-server-<name>`, category debian, enabled	Set the server’s credentials (Credentials and secrets)
Removal of the entry on uninstall	Grant users access and let them select it (Granting access)
	Check that it starts: `sudo mcprack server test mcp-server-<name>`

If you change the entry by hand (extra --set-env values, another label) a later upgrade of the companion runs server create again, which updates the same entry; keep your credentials in the secret store, not in the registration.

Command-line options the packages use¶

Option	Meaning
`--transport stdio`	The server speaks MCP over standard input/output; mcprack runs it per user
`--command`	Absolute path of the installed binary
`--category debian`	Groups these entries in the catalog
`--set-env KEY=VALUE`	A non-secret environment value (needs mcprack 1.5.4 or newer)

The command must also pass mcprack’s command policy (Policies for commands, URLs and installs); /usr/bin/... always does.