github.com/aclaygray/packer@v1.3.2/website/source/docs/other/debugging.html.md (about) 1 --- 2 description: | 3 Packer strives to be stable and bug-free, but issues inevitably arise where 4 certain things may not work entirely correctly, or may not appear to work 5 correctly. 6 layout: docs 7 page_title: 'Debugging - Other' 8 sidebar_current: 'docs-other-debugging' 9 --- 10 11 # Debugging Packer Builds 12 13 Using `packer build -on-error=ask` allows you to inspect failures and try out 14 solutions before restarting the build. 15 16 For remote builds with cloud providers like Amazon Web Services AMIs, debugging 17 a Packer build can be eased greatly with `packer build -debug`. This disables 18 parallelization and enables debug mode. 19 20 Debug mode informs the builders that they should output debugging information. 21 The exact behavior of debug mode is left to the builder. In general, builders 22 usually will stop between each step, waiting for keyboard input before 23 continuing. This will allow you to inspect state and so on. 24 25 In debug mode once the remote instance is instantiated, Packer will emit to the 26 current directory an ephemeral private ssh key as a .pem file. Using that you 27 can `ssh -i <key.pem>` into the remote build instance and see what is going on 28 for debugging. The key will only be emitted for cloud-based builders. The 29 ephemeral key will be deleted at the end of the packer run during cleanup. 30 31 For a local builder, the SSH session initiated will be visible in the detail 32 provided when `PACKER_LOG=1` environment variable is set prior to a build, 33 and you can connect to the local machine using the userid and password defined 34 in the kickstart or preseed associated with initializing the local VM. 35 36 It should be noted that one of the options `-on-error` is to `retry`, the retry 37 of the step in question has limitations: 38 39 * the template packer is building is **not** reloaded from file. 40 * the resources specified from builders **are** reloaded from file. 41 42 Check the specfics on your builder to confirm their behavior. 43 44 ### Windows 45 46 As of Packer 0.8.1 the default WinRM communicator will emit the password for a 47 Remote Desktop Connection into your instance. This happens following the several 48 minute pause as the instance is booted. Note a .pem key is still created for 49 securely transmitting the password. Packer automatically decrypts the password 50 for you in debug mode. 51 52 ## Debugging Packer 53 54 Issues occasionally arise where certain things may not work entirely correctly, 55 or may not appear to work correctly. In these cases, it is sometimes helpful to 56 see more details about what Packer is actually doing. 57 58 Packer has detailed logs which can be enabled by setting the `PACKER_LOG` 59 environmental variable to any value but `""` (empty string) and `"0"` like this 60 `PACKER_LOG=1 packer build <config.json>`. This will cause detailed logs to 61 appear on stderr. The logs contain log messages from Packer as well as any 62 plugins that are being used. Log messages from plugins are prefixed by their 63 application name. 64 65 Note that because Packer is highly parallelized, log messages sometimes appear 66 out of order, especially with respect to plugins. In this case, it is important 67 to pay attention to the timestamp of the log messages to determine order. 68 69 In addition to simply enabling the log, you can set `PACKER_LOG_PATH` in order 70 to force the log to always go to a specific file when logging is enabled. Note 71 that even when `PACKER_LOG_PATH` is set, `PACKER_LOG` must be set in order for 72 any logging to be enabled. 73 74 ### Debugging Packer in Powershell/Windows 75 76 In Windows you can set the detailed logs environmental variable `PACKER_LOG` or 77 the log variable `PACKER_LOG_PATH` using powershell environment variables. For 78 example: 79 80 ``` powershell 81 $env:PACKER_LOG=1 82 $env:PACKER_LOG_PATH="packerlog.txt" 83 ``` 84 85 If you find a bug with Packer, please include the detailed log by using a 86 service such as [gist](https://gist.github.com). 87 88 ## Issues Installing Ubuntu Packages 89 90 Issues may arise using and building Ubuntu AMIs where common packages that 91 *should* be installed from Ubuntu's Main repository are not found during a 92 provisioner step: 93 94 amazon-ebs: No candidate version found for build-essential 95 amazon-ebs: No candidate version found for build-essential 96 97 This, obviously can cause problems where a build is unable to finish 98 successfully as the proper packages cannot be provisioned correctly. The problem 99 arises when cloud-init has not finished fully running on the source AMI by the 100 time that packer starts any provisioning steps. 101 102 Adding the following provisioner to the packer template, allows for the 103 cloud-init process to fully finish before packer starts provisioning the source 104 AMI. 105 106 ``` json 107 { 108 "type": "shell", 109 "inline": [ 110 "while [ ! -f /var/lib/cloud/instance/boot-finished ]; do echo 'Waiting for cloud-init...'; sleep 1; done" 111 ] 112 } 113 ``` 114 115 ## Issues when using numerous Builders/Provisioners/Post-Processors 116 117 Packer uses a separate process for each builder, provisioner, post-processor, 118 and plugin. In certain cases, if you have too many of these, you can run out of 119 [file descriptors](https://en.wikipedia.org/wiki/File_descriptor). This results 120 in an error that might look like 121 122 ``` text 123 error initializing provisioner 'powershell': fork/exec /files/go/bin/packer: 124 too many open files 125 ``` 126 127 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. 128 129 ## Issues when using long temp directory 130 131 Packer uses unix sockets internally, which are created inside the default 132 directory for temporary files. Some operating systems place a limit on the 133 length of the socket name, usually between 80 and 110 characters. If you get an 134 error like this (for any builder, not just docker): 135 136 ``` text 137 Failed to initialize build 'docker': error initializing builder 'docker': plugin exited before we could connect 138 ``` 139 140 you should try setting your temp directory to something shorter. This can be 141 done through the `TMPDIR` environment variable.