diff --git a/docs/reference/stacker_file.md b/docs/reference/stacker_file.md index a39d0fd..4fab9ba 100644 --- a/docs/reference/stacker_file.md +++ b/docs/reference/stacker_file.md @@ -1,13 +1,15 @@ # The `stacker.yaml` file -When doing a `stacker build`, the behavior of stacker is specified by the yaml -directives below. In addition to these, stacker allows variable substitions of -several forms. For example, a line like: +During a stacker build, the behavior of stacker is specified by yaml directives in a `stacker.yaml` file, as described in this document. + +## Substitutions and variables + +In the yaml directives, stacker allows variable substitions of several forms. For example, these three substition statements: $ONE ${{TWO}} ${{THREE:3}} -When run with `stacker build --substitute ONE=1 --substitute TWO=2` is -processed in stacker as: +when run with `stacker build --substitute ONE=1 --substitute TWO=2` are +processed by stacker as: 1 2 3 @@ -21,17 +23,18 @@ In order to avoid confusion, it is also an error if a placeholder in the shell s Substitutions can also be specified in a yaml file given with the argument `--substitute-file`, with any number of key: value pairs: + ONE: 1 + TWO: 2 FOO: bar BAZ: bat -In addition to substitutions provided on the command line or a file, the following variables are also available with their values from either command line flags or stacker-config file. +In addition to substitutions provided on the command line or in a file, the following variables are also available with their values from either command line flags or stacker-config file. STACKER_STACKER_DIR config name 'stacker_dir', cli flag '--stacker-dir'- STACKER_ROOTFS_DIR config name 'rootfs_dir', cli flag '--roots-dir' STACKER_OCI_DIR config name 'oci_dir', cli flag '--oci-dir' -The stacker build environment has the following environment variables -available for reference: +The stacker build environment has the following environment variables available for reference: * `STACKER_LAYER_NAME`: the name of the layer being built. `STACKER_LAYER_NAME` will be `my-build` when the `run` section below is executed. @@ -40,6 +43,8 @@ available for reference: run: echo "Your layer is ${STACKER_LAYER_NAME}" ``` +## YAML directives + ### `from` The `from` directive describes the base image that stacker will start from. It takes the form: diff --git a/docs/user_guide/template_substitution.md b/docs/user_guide/template_substitution.md index 21a990d..f0db65d 100644 --- a/docs/user_guide/template_substitution.md +++ b/docs/user_guide/template_substitution.md @@ -1,27 +1,46 @@ # Template Variable Substitution -When doing a `stacker build`, the behavior of stacker is specified by the YAML -directives below. In addition to these, stacker allows variable substitions of -several forms. For example, a line like: +In the yaml directives that direct a stacker build, stacker allows variable substitions of several forms. For example, these three substition statements: $ONE ${{TWO}} ${{THREE:3}} -When run with `stacker build --substitute ONE=1 --substitute TWO=2` is -processed in stacker as: +when run with `stacker build --substitute ONE=1 --substitute TWO=2` are +processed by stacker as: 1 2 3 -That is, variables of the form `$FOO` or `${FOO}` are supported, and variables -with `${FOO:default}` a default value will evaluate to their default if not -specified on the command line. It is an error to specify a `${FOO}` style -without a default; to make the default an empty string, use `${FOO:}`. +In order to avoid conflict with bash or POSIX shells in the `run` section, only placeholders with two braces are supported, such as `${{FOO}}`. Placeholders with a default value like `${{FOO:default}}` will evaluate to their default if not specified on the command line or in a substitution file. -You can also declare variable substitutions in a separate file which is then included in the build command as in this example: +Using a `${{FOO}}` placeholder without a default will result in an error if there is no substitution provided. If you want an empty string in that case, use an empty default: `${{FOO:}}`. + +In order to avoid confusion, it is also an error if a placeholder in the shell style (`$FOO` or `${FOO}`) is found when the same key has been provided as a substitution either via the command line (for example, `--substitute FOO=bar`) or in a substitution file. An error will be reported with an explanation for how to rewrite it, as in this example: + + error "A=B" was provided as a substitution and unsupported placeholder "${A}" was found. Replace "${A}" with "${{A}}" to use the substitution. + +Substitutions can also be specified in a separate yaml file using the argument `--substitute-file` in the build command, as in this example: `stacker build --substitute-file ` -The substitution file simply contains KEY:VALUE pairs, as in this example: +The substitution file simply contains any number of KEY:VALUE pairs, as in this example: $ cat stacker-subs.yaml + ONE: 1 TWO: 2 + FOO: bar + BAZ: bat + +In addition to substitutions provided on the command line or in a file, the following variables are also available with their values from either command line flags or stacker-config file. + + STACKER_STACKER_DIR config name 'stacker_dir', cli flag '--stacker-dir'- + STACKER_ROOTFS_DIR config name 'rootfs_dir', cli flag '--roots-dir' + STACKER_OCI_DIR config name 'oci_dir', cli flag '--oci-dir' + +The stacker build environment has the following environment variables available for reference: + + * `STACKER_LAYER_NAME`: the name of the layer being built. `STACKER_LAYER_NAME` will be `my-build` when the `run` section below is executed. + + ```yaml + my-build: + run: echo "Your layer is ${STACKER_LAYER_NAME}" + ```