Defining the build and runtime environment

When it comes to the application directory, the builder user/UID and group/GID, and environment variables, Blubber behaves with a set of opinionated default values. However, you can tweak any one of these values.

Background

Given examples/hello-world as a working directory.

Rely on the default values

Given this "blubber.yaml"

version: v4
variants:
  hello:
    base: debian:bullseye
    copies: [local]
    entrypoint: [./hello.sh]

When you build the "hello" variant

Then the image will have the user "somebody" with UID 65533

And the image will have the group "somebody" with GID 65533

And the image will have the user "runuser" with UID 900

And the image will have the group "runuser" with GID 900

And the image will have the following files in "/srv/app"

owner	group	name
65533	65533	README.md
65533	65533	hello.sh

And the image runtime user will be "900"

And the image entrypoint will be "./hello.sh".

Customize the application location and file owner

Given this "blubber.yaml"

version: v4
lives:
  in: /usr/local/app
  as: appowner
  uid: 1234
  gid: 1235
variants:
  hello:
    base: debian:bullseye
    copies: [local]
    entrypoint: [./hello.sh]

When you build the "hello" variant

Then the image will have the user "appowner" with UID 1234

And the image will have the group "appowner" with GID 1235

And the image will have the following files in "/usr/local/app"

owner	group	name
1234	1235	README.md
1234	1235	hello.sh

Customize the runtime process owner

Given this "blubber.yaml"

version: v4
runs:
  as: apprunner
  uid: 4321
  gid: 4320
variants:
  hello:
    base: debian:bullseye
    copies: [local]
    entrypoint: [./hello.sh]

When you build the "hello" variant

Then the image will have the user "apprunner" with UID 4321

And the image will have the group "apprunner" with GID 4320

And the image runtime user will be "4321".

Disable the unprivileged runtime process owner

Given this "blubber.yaml"

version: v4
lives:
  uid: 1234
runs:
  insecurely: true
  uid: 4321
variants:
  hello:
    base: debian:bullseye
    copies: [local]
    entrypoint: [./hello.sh]

When you build the "hello" variant

Then the image runtime user will be "1234".

Defining extra environment variables

Given this "blubber.yaml"

version: v4
runs:
  environment:
    FOO: bar
    BAZ: qux
variants:
  hello:
    base: debian:bullseye
    copies: [local]
    entrypoint: [./hello.sh]

When you build the "hello" variant

Then the image will include environment variables

FOO=bar
BAZ=qux

Changing the default runtime directory

Given this "blubber.yaml"

version: v4
runs:
  in: /some/other/directory
variants:
  hello:
    base: debian:bullseye
    copies: [local]
    entrypoint: [./hello.sh]

When you build the "hello" variant

Then the image runtime directory will be "/some/other/directory".