152 lines
6.1 KiB
Plaintext
152 lines
6.1 KiB
Plaintext
---
|
|
description: |
|
|
Packer strives to be stable and bug-free, but issues inevitably arise where
|
|
certain things may not work entirely correctly, or may not appear to work
|
|
correctly.
|
|
page_title: Debugging - Other
|
|
---
|
|
|
|
# Debugging Packer Builds
|
|
|
|
Using `packer build -on-error=ask` allows you to inspect failures and try out
|
|
solutions before restarting the build.
|
|
|
|
For remote builds with cloud providers like Amazon Web Services AMIs, debugging
|
|
a Packer build can be eased greatly with `packer build -debug`. This disables
|
|
parallelization and enables debug mode.
|
|
|
|
Debug mode informs the builders that they should output debugging information.
|
|
The exact behavior of debug mode is left to the builder. In general, builders
|
|
usually will stop between each step, waiting for keyboard input before
|
|
continuing. This will allow you to inspect state and so on.
|
|
|
|
In debug mode once the remote instance is instantiated, Packer will emit to the
|
|
current directory an ephemeral private SSH key as a .pem file. Using that you
|
|
can `ssh -i <key.pem>` into the remote build instance and see what is going on
|
|
for debugging. The key will only be emitted for cloud-based builders. The
|
|
ephemeral key will be deleted at the end of the Packer run during cleanup.
|
|
|
|
For a local builder, the SSH session initiated will be visible in the detail
|
|
provided when `PACKER_LOG=1` environment variable is set prior to a build, and
|
|
you can connect to the local machine using the userid and password defined in
|
|
the kickstart or preseed associated with initializing the local VM.
|
|
|
|
It should be noted that one of the options `-on-error` is to `retry`, the retry
|
|
of the step in question has limitations:
|
|
|
|
- the template Packer is building is **not** reloaded from file.
|
|
- the resources specified from builders **are** reloaded from file.
|
|
|
|
Check the specifics on your builder to confirm their behavior.
|
|
|
|
### Windows
|
|
|
|
As of Packer 0.8.1 the default WinRM communicator will emit the password for a
|
|
Remote Desktop Connection into your instance. This happens following the
|
|
several minute pause as the instance is booted. Note a .pem key is still
|
|
created for securely transmitting the password. Packer automatically decrypts
|
|
the password for you in debug mode.
|
|
|
|
## Debugging Packer
|
|
|
|
Issues occasionally arise where certain things may not work entirely correctly,
|
|
or may not appear to work correctly. In these cases, it is sometimes helpful to
|
|
see more details about what Packer is actually doing.
|
|
|
|
Packer has detailed logs which can be enabled by setting the `PACKER_LOG`
|
|
environmental variable to any value but `""` (empty string) and `"0"` like this
|
|
`PACKER_LOG=1 packer build <config.json>`. This will cause detailed logs to
|
|
appear on stderr. The logs contain log messages from Packer as well as any
|
|
plugins that are being used. Log messages from plugins are prefixed by their
|
|
application name.
|
|
|
|
Note that because Packer is highly parallelized, log messages sometimes appear
|
|
out of order, especially with respect to plugins. In this case, it is important
|
|
to pay attention to the timestamp of the log messages to determine order.
|
|
|
|
In addition to simply enabling the log, you can set `PACKER_LOG_PATH` in order
|
|
to force the log to always go to a specific file when logging is enabled. Note
|
|
that even when `PACKER_LOG_PATH` is set, `PACKER_LOG` must be set in order for
|
|
any logging to be enabled.
|
|
|
|
### Debugging Plugins
|
|
|
|
Each packer plugin runs in a separate process and communicates with RCP over a
|
|
socket therefore using a debugger will not work (be complicated at least).
|
|
|
|
But most of the Packer code is really simple and easy to follow with PACKER_LOG
|
|
turned on. If that doesn't work adding some extra debug print outs when you have
|
|
homed in on the problem is usually enough.
|
|
|
|
### Debugging Packer in Powershell/Windows
|
|
|
|
In Windows you can set the detailed logs environmental variable `PACKER_LOG` or
|
|
the log variable `PACKER_LOG_PATH` using powershell environment variables. For
|
|
example:
|
|
|
|
```powershell
|
|
$env:PACKER_LOG=1
|
|
$env:PACKER_LOG_PATH="packerlog.txt"
|
|
```
|
|
|
|
If you find a bug with Packer, please include the detailed log by using a
|
|
service such as [gist](https://gist.github.com).
|
|
|
|
## Issues Installing Ubuntu Packages
|
|
|
|
Issues may arise using and building Ubuntu AMIs where common packages that
|
|
_should_ be installed from Ubuntu's Main repository are not found during a
|
|
provisioner step:
|
|
|
|
```text
|
|
amazon-ebs: No candidate version found for build-essential
|
|
amazon-ebs: No candidate version found for build-essential
|
|
```
|
|
|
|
This, obviously can cause problems where a build is unable to finish
|
|
successfully as the proper packages cannot be provisioned correctly. The
|
|
problem arises when cloud-init has not finished fully running on the source AMI
|
|
by the time that packer starts any provisioning steps.
|
|
|
|
Adding the following provisioner to the Packer template, allows for the
|
|
cloud-init process to fully finish before packer starts provisioning the source
|
|
AMI.
|
|
|
|
```json
|
|
{
|
|
"type": "shell",
|
|
"inline": [
|
|
"while [ ! -f /var/lib/cloud/instance/boot-finished ]; do echo 'Waiting for cloud-init...'; sleep 1; done"
|
|
]
|
|
}
|
|
```
|
|
|
|
## Issues when using numerous Builders/Provisioners/Post-Processors
|
|
|
|
Packer uses a separate process for each builder, provisioner, post-processor,
|
|
and plugin. In certain cases, if you have too many of these, you can run out of
|
|
[file descriptors](https://en.wikipedia.org/wiki/File_descriptor). This results
|
|
in an error that might look like
|
|
|
|
```text
|
|
error initializing provisioner 'powershell': fork/exec /files/go/bin/packer:
|
|
too many open files
|
|
```
|
|
|
|
On Unix systems, you can check what your file descriptor limit is with
|
|
`ulimit -Sn`. You should check with your OS vendor on how to raise this limit.
|
|
|
|
## Issues when using long temp directory
|
|
|
|
Packer uses unix sockets internally, which are created inside the default
|
|
directory for temporary files. Some operating systems place a limit on the
|
|
length of the socket name, usually between 80 and 110 characters. If you get an
|
|
error like this (for any builder, not just docker):
|
|
|
|
```text
|
|
Failed to initialize build 'docker': error initializing builder 'docker': plugin exited before we could connect
|
|
```
|
|
|
|
you should try setting your temp directory to something shorter. This can be
|
|
done through the `TMPDIR` environment variable.
|