How to include cloud-config files from removable devices​
Elemental nodes support loading cloud-config files from specific block devices.
In particular supports loading cloud-config files from an ISO having CIDATA
as the volume ID or any vFAT formatted
device labeled with CIDATA
. If a device matching this criteria is found on early boot the Elemental client will
read it and look for a user-data
file in its root.
As an example an ISO including a cloud-config file can be created on a Linux host with the procedure below.
Create a user-data
file with the cloud-config data in it. In the example below we just set a
proxy:
#cloud-config
write_files:
- path: /etc/sysconfig/proxy
append: true
content: |
PROXY_ENABLED="yes"
HTTP_PROXY=http://some.domain.org:8080
HTTPS_PROXY=https://some.domain.org:8080
NO_PROXY="localhost, 127.0.0.1"
Once the user-data
file exists create an ISO including only this file by using the mkisofs
Linux utility:
mkisof -o cidata.iso -V CIDATA -J -r user-data
The result is an ISO labeled with CIDATA
including the user-data
file.
At boot the user-data
file will be copied as is to /oem/user-data
and in case it contains cloud-config data
an extra copy will be added as /oem/user-data.yaml
. The file /oem/user-data.yaml
will be parsed
on any later cloud-init stage.
Since the data is copied to /oem
it will be persistent, hence on follow up reboots the removable device is
not required to be present any more. If still present on follow up reboots, it just overwrites any
aleady pre-existing data.
Include non cloud-config data​
If the user-data
is not containing cloud-config data the Elemental client will just copy it as
is to /oem/user-data
. Only *.yaml
files are parsed when executing cloud-init stages, so in that
case the file will be ignored by cloud-init services.
If the user-data
contains a script the Elemental client will, in addition, try to execute it. The way
Elemental client determines if user-data
is a script or not is by the presence of a Shebang in the
first line. For example, the previous user-data
file could be rewritten as:
#!/bin/bash
cat <<EOF >> /etc/sysconfig/proxy
PROXY_ENABLED="yes"
HTTP_PROXY=http://some.domain.org:8080
HTTPS_PROXY=https://some.domain.org:8080
NO_PROXY="localhost, 127.0.0.1"
EOF