generic

VM Framework - Generic Layer

This is a generic Linux VM build layer designed for simplicity and flexibility.

It is compatible with any base layer (just make sure the SSH server is installed and properly configured).

Provisioning Stages

It consists of following stages (note: all script stages are optional and will not error if they do not exist!):

1. Sync files from a local vm_scripts_src path (defaults to scripts/ relative to the packer file, so make sure you use absolute path inside your Makefile!) onto the VM (hardcoded path: /opt/vm-scripts/ -- used as base for all other stages!);

2. Execute the vm-prepare.sh scripts (from the synced scripts dir); you can use this to setup / symlink the scripts for the two stages following it (see the example);

3. Execute the first installation stage (sorted scripts inside install-stage1.d vm-scripts path); the last script may issue an optional reboot, it will be properly awaited by Packer; you can use this stage to fix networking and do kernel / bootloader-level configuration (e.g., net.ifnames cmline options);

4. Execute the second (and last) stage (install-stage2.d); in here, you should put all other scripts expecting a proper kernel setup (ran after the reboot);

You can include (or simply inspire from) the layer's build.mk containing the VM framework macros to use for building a VM.

Important scripts syncing note: Packer uses rsync semantics for copying files onto the VM, so if you want to copy the contents of a directory only, make sure to end it with / (slash)!

Usage

To get started, simply include layer's build.mk and call the vm_new_layer_generic macro:

include $(FRAMEWORK_DIR)/layers/generic/build.mk

# creates the `main` VM using defaults
$(call vm_new_layer_generic,main)
# override the name and source scripts
main-name = examplevm_$(examplevm-ver)
# Note: make sure the directory ends with '/' so its contents are copied!
main-copy-scripts = $(abspath ./main/scripts)/
# the *-copy-scripts is a list, so you can sync multiple directories, e.g.:
#main-copy-scripts += $(abspath ./vm-prepare.sh) $(abspath ./overrides)/

Note: this generic layer does NOT customize anything on the VM image -- it is meant to be used as a starter layer for further extensions, so you must add your own install snippets inside the appropiate provisioning directories executed.

See the full-featured layer for an advanced example of defining layers on top of this, or the example template.