[Maas-devel] ephemeral image debugging

[Scott Moser]

Hey all,

Whenever people have problems with enlistment or commissioning, often
times debugging from within the ephemeral image is needed to see whats
going on.

Below is a general "how to get around" guide.

### backdoor (add a login) to ephemeral images ###
# If you cannot login to an instance, you might have to "backdoor it"
# in order to see what is going wrong.  I wrote a simple utility
# that injects a user and password into an image.  Heres how to
# add a 'backdoor' user with a password to your images.
bzr branch lp:~smoser/+junk/backdoor-image
imgs=$(echo var/lib/maas/ephemeral/*/*/*/*/*.img)
for img in $imgs; do
  [ -f "$img.dist" ] || cp -a --sparse=always $img.dist
done
for img in $imgs; do
  sudo ./backdoor-image -v --user=backdoor --password-auth --password=ubuntu
done

### Inside the ephemeral image  ###

## Important files for debugging:
# Someone is likely to ask you for these things to help debug
/var/log/cloud-init.log
/var/log/boot.log
/var/log/cloud-init-output.log

# After enlistment or commissioning, the user-data from maas instructs
# the system to poweroff.  To stop that from happening, you can just
# touch a file in /tmp.
touch /tmp/block-poweroff

## maas credentials:
# maas credentials can be found in 2 places:
# * from the cmdline you'll see a 'url=' or 'cloud-config-url=' parameter
#   You can get the cloud-config from that url, which will have
#   credentials.
#   example:
#    $ sed -n 's,.*url=\([^ ]*\).*,\1,p' /proc/cmdline
#    http://10.55.60.194/MAAS/metadata/latest/enlist-preseed/?op=get_enlist_preseed
# * from /etc/cloud/cloud.cfg.d/91_kernel_cmdline_url
#   The file was pulled from url= parameter by cloud-init
#   $ sudo cat /etc/cloud/cloud.cfg.d/91_kernel_cmdline

### maas datasource ###
# the cloud-init datasource for MAAS can be invoked as a 'main' for
# debugging purposes. To do so, you need to know the url for the maas
# datasource and a config file that contains credentials.
#
$ cfg=$(echo /etc/cloud/cloud.cfg.d/*_cmdline_url.cfg)
$ echo $cfg
/etc/cloud/cloud.cfg.d/91_kernel_cmdline_url.cfg

# now get the metadata_url from there.
$ url=$(sudo awk '$1 == "metadata_url:" { print $2 }' $cfg)
$ echo $url
http://10.55.60.194/MAAS/metadata/enlist

# invoke the client
# /usr/share/pyshared/cloudinit/sources/DataSourceMAAS.py
# the client has --help Usage also, but here is an example on how
# to use it.
$ maasds="/usr/share/pyshared/cloudinit/sources/DataSourceMAAS.py"
$ sudo python $maasds --config=$cfg get $url
== http://10.55.60.194/MAAS/metadata/enlist ==
2012-03-01
latest

$ sudo python $maasds --config=$cfg get $url/latest/meta-data/local-hostname
maas-enlisting-node