cloud-init execution order doesn't respect /etc/cloud/cloud.cfg? - user-data

Question

This is the content of /etc/cloud/cloud.cfg of Ubuntu cloud 16.04 image:
# The top level settings are used as module
# and system configuration.
# A set of users which may be applied and/or used by various modules
# when a 'default' entry is found it will reference the 'default_user'
# from the distro configuration specified below
users:
- default
# If this is set, 'root' will not be able to ssh in and they
# will get a message to login instead as the above $user (ubuntu)
disable_root: true
# This will cause the set+update hostname module to not operate (if true)
preserve_hostname: false
# Example datasource config
# datasource:
# Ec2:
# metadata_urls: [ 'blah.com' ]
# timeout: 5 # (defaults to 50 seconds)
# max_wait: 10 # (defaults to 120 seconds)
# The modules that run in the 'init' stage
cloud_init_modules:
- migrator
- ubuntu-init-switch
- seed_random
- bootcmd
- write-files
- growpart
- resizefs
- disk_setup
- mounts
- set_hostname
- update_hostname
- update_etc_hosts
- ca-certs
- rsyslog
- users-groups
- ssh
# The modules that run in the 'config' stage
cloud_config_modules:
# Emit the cloud config ready event
# this can be used by upstart jobs for 'start on cloud-config'.
- emit_upstart
- snap_config
- ssh-import-id
- locale
- set-passwords
- grub-dpkg
- apt-pipelining
- apt-configure
- ntp
- timezone
- disable-ec2-metadata
- runcmd
- byobu
# The modules that run in the 'final' stage
cloud_final_modules:
- snappy
- package-update-upgrade-install
- fan
- landscape
- lxd
- puppet
- chef
- salt-minion
- mcollective
- rightscale_userdata
- scripts-vendor
- scripts-per-once
- scripts-per-boot
- scripts-per-instance
- scripts-user
- ssh-authkey-fingerprints
- keys-to-console
- phone-home
- final-message
- power-state-change
# System and/or distro specific settings
# (not accessible to handlers/transforms)
system_info:
# This will affect which distro class gets used
distro: ubuntu
# Default user name + that default users groups (if added/used)
default_user:
name: ubuntu
lock_passwd: True
gecos: Ubuntu
groups: [adm, audio, cdrom, dialout, dip, floppy, lxd, netdev, plugdev, sudo, video]
sudo: ["ALL=(ALL) NOPASSWD:ALL"]
shell: /bin/bash
# Other config here will be given to the distro class and/or path classes
paths:
cloud_dir: /var/lib/cloud/
templates_dir: /etc/cloud/templates/
upstart_dir: /etc/init/
package_mirrors:
- arches: [i386, amd64]
failsafe:
primary: http://archive.ubuntu.com/ubuntu
security: http://security.ubuntu.com/ubuntu
search:
primary:
- http://%(ec2_region)s.ec2.archive.ubuntu.com/ubuntu/
- http://%(availability_zone)s.clouds.archive.ubuntu.com/ubuntu/
- http://%(region)s.clouds.archive.ubuntu.com/ubuntu/
security: []
- arches: [armhf, armel, default]
failsafe:
primary: http://ports.ubuntu.com/ubuntu-ports
security: http://ports.ubuntu.com/ubuntu-ports
ssh_svcname: ssh
As you can see, package-update-upgrade-install is put in final stage, where runcmd is put in config stage. According to cloud-init document, modules in config stage are executed before final stage. As I understand, runcmd will be executed before package install.
However, the following code runs without any error:
packages:
- shorewall
runcmd:
- echo "printing shorewall version"
- shorewall version
That means runcmd can be executed after package install.
Is there any reason that make cloud-init disrespect the execution order defined in /etc/cloud/cloud.cfg?

Answer 1

While investigating how to get cloud-init to run things earlier in the boot process, I saw this too. In my testing, it appeared to me that runcmd was running in the config stage as you would expect, but all it was doing was creating a shell script from the runcmd data, which it put in /var/lib/cloud/instance/scripts/runcmd. Cloud-init then ran the shell script during the scripts-user module in the final stage. Below are bits from the /var/log/cloud-init.log log showing this:
"Mar 15 17:12:24 cloud-init[2796]: stages.py[DEBUG]: Running module runcmd (<module 'cloudinit.config.cc_runcmd' from '/usr/lib/python2.7/dist-packages/cloudinit/config/cc_runcmd.pyc'>) with frequency once-per-instance",
"Mar 15 17:12:24 cloud-init[2796]: util.py[DEBUG]: Writing to /var/lib/cloud/instances/i-xxx/sem/config_runcmd - wb: [644] 20 bytes",
"Mar 15 17:12:24 cloud-init[2796]: helpers.py[DEBUG]: Running config-runcmd using lock (<FileLock using file '/var/lib/cloud/instances/i-xxx/sem/config_runcmd'>)",
"Mar 15 17:12:24 cloud-init[2796]: util.py[DEBUG]: Shellified 1 commands.",
"Mar 15 17:12:24 cloud-init[2796]: util.py[DEBUG]: Writing to /var/lib/cloud/instances/i-xxx/scripts/runcmd - wb: [700] 50 bytes",
...
"Mar 15 17:12:40 cloud-init[2945]: stages.py[DEBUG]: Running module scripts-user (<module 'cloudinit.config.cc_scripts_user' from '/usr/lib/python2.7/dist-packages/cloudinit/config/cc_scripts_user.pyc'>) with frequency once-per-instance",
"Mar 15 17:12:40 cloud-init[2945]: util.py[DEBUG]: Writing to /var/lib/cloud/instances/i-xxx/sem/config_scripts_user - wb: [644] 20 bytes",
"Mar 15 17:12:40 cloud-init[2945]: helpers.py[DEBUG]: Running config-scripts-user using lock (<FileLock using file '/var/lib/cloud/instances/i-xxx/sem/config_scripts_user'>)",
"Mar 15 17:12:40 cloud-init[2945]: util.py[DEBUG]: Running command ['/var/lib/cloud/instance/scripts/runcmd'] with allowed return codes [0] (shell=True, capture=False)",
Hope this helps...