6df7921cb7
When using simple-init, we are making an explicit choice along the lines of "I want the simple tool to do the simple needful" which works well, except when cloud-init tries to run because it is already baked into the source image diskimage-builder started with. So what would happen is Glean would execute from simple-init, and then cloud-init would get launched by default, and cloud-init in some cases everything is DHCP, so suddenly any static configuration, such as what might be in an attached configuration drive, is stomped upon resulting in an unreachable instance if DHCP is just not available. If DHCP is available, generally this is not an issue and goes un-noticed, yet can add a substantial amount of time to the boot sequence "waiting" for meta-data endpoints which may not exist. Change-Id: I380b9638cd28f5771530089c558ef5ab638c0173
simple-init
Basic network and system configuration that can't be done until boot
Unfortunately, as much as we'd like to bake it in to an image, we can't know in advance how many network devices will be present, nor if DHCP is present in the host cloud. Additionally, in environments where cloud-init is not used, there are a couple of small things, like mounting config-drive and pulling ssh keys from it, that need to be done at boot time.
Note
This element removes cloud-init as it can stomp on the configuration applied by glean, resulting in additional problems for operators, and a more difficult path troubleshooting.
Autodetect network interfaces during boot and configure them
The rationale for this is that we are likely to require multiple network interfaces for use cases such as baremetal and there is no way to know ahead of time which one is which, so we will simply run a DHCP client on all interfaces with real MAC addresses (except lo) that are visible on the first boot.
The script /usr/local/sbin/simple-init.sh will be called early in each boot and will scan available network interfaces and ensure they are configured properly before networking services are started.
Processing startup information from config-drive
On most systems, the DHCP approach desribed above is fine. But in some clouds, such as Rackspace Public cloud, there is no DHCP. Instead, there is static network config via config-drive. simple-init will happily call glean which will do nothing if static network information is not there.
Finally, glean will handle ssh-keypair-injection from config drive if cloud-init is not installed.
Chosing glean installation source
By default glean is installed using pip using the latest release on pypi. It is also possible to install glean from a specified git repository location. This is useful for debugging and testing new glean changes for example. To do this you need to set these variables:
DIB_INSTALLTYPE_simple_init=repo
DIB_REPOLOCATION_glean=/path/to/glean/repo
DIB_REPOREF_glean=name_of_git_refFor example to test glean change 364516 do:
git clone https://opendev.org/opendev/glean /tmp/glean
cd /tmp/glean
git review -d 364516
git checkout -b my-test-refThen set your DIB env vars like this before running DIB:
DIB_INSTALLTYPE_simple_init=repo
DIB_REPOLOCATION_glean=/tmp/glean
DIB_REPOREF_glean=my-test-refNetworkManager
By default, this uses the "legacy" scripts on each platform. To use
NetworkManager instead, set DIB_SIMPLE_INIT_NETWORKMANAGER
to non-zero. See the glean documentation for what the implications for
this are on each platform.
This is currently only implemented for CentOS and Fedora platforms.
Fallback
Glean falls back to DHCPv4 for all interfaces that do not have an explicit configuration. If this is not desired, set the following variable to disable the fallback and leave such interfaces unconfigured:
export DIB_SIMPLE_INIT_NO_DHCP_FALLBACK=1