Run bash script from template_file

[Thorvald Hallvardsson]

Hi everyone,

I'm trying to run a bash script from the template_file... as I found that's the only method to run commands without passing a file name. I simply want to keep my terraform file simple. 

So I'm using something like:

resource "aws_instance" "ubuntu" {

  ami = "${data.aws_ami.ubuntu.id}"

  instance_type = "t2.micro"

  key_name = "key1"

  tags {

    Name = "ubuntu"

  }

  security_groups = [ "default" ]

  user_data =  "${data.template_file.bootstrap_shell.rendered}"

}

data "template_file" "bootstrap_shell" {

  template = <<-EOF

              #!/bin/bash

              apt-get install whois

              EOF

}

And absolutely nothing happens.

When I run curl http://169.254.169.254/latest/user-data/

it returns

#!/bin/bash

apt-get install whois

So everything is good it's just not executing the commands.

Any ideas?

Thank you.

Regards.

[David Adams]

Does it return exactly what you posted or are there leading spaces in front of the `#!/bin/bash`? If there are leading spaces, that's the problem.

Otherwise, have you checked syslog/dmesg/console output for what cloud-init is saying about running that script?

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[Philip Nelson]

check out null_resource with it's local-exec option, that's what you are looking for. 

On Fri, May 5, 2017 at 7:06 AM, Thorvald Hallvardsson <thorvald.h...@gmail.com> wrote:

--

[Thorvald Hallvardsson]

Yes, exactly the same thing no spaces on the front, nothing what would indicate some processing errors etc. No logs at all saying cloud init executed something I asked it to...

I don't want to use local-exec option requires SSH connection to finish the task and I don't want to use SSH session at all.

Thanks!

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[Philip Nelson]

I must be missing something here. local-exec runs on the local computer, no ssh. you appear to be wanting to run apt-get install whois, .... somewhere. What you are doing gets you a string with the commands you want in it. Uou could put somewhere, say a remote file, though you haven't used it's rendered output to do that, but nothing to execute it, that isn't it's job. 

If you want to execute that script you "wrote" in data.template_file, the simplest way would be to turn that into an instance startup script, aka userdata in aws. Terraform doesn't give you a way, other than userdata (with aws) or remote-exec, with ssh to do anything on a host. 

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[Thorvald Hallvardsson]

Sorry, I got that wrong. Forget about the local-exec.

As you could clearly see from my first example I invoke user_data ... or rather I'm trying to invoke it from terraform. User_data is going to install whois during the bootstrap process. I can run remote-exec or even provision a file and then run remote-exec the thing is... I don't want to use SSH connection at all. By passing a data to user_data my 'script' runs from the cloud-init which doesn't require any SSH connection. It's the part of the booting process (or rather instance creation). 

As soon as I use {$file('filename')} as a user_data it works absolutely fine. But when I'm trying to operate just on a text ... it doesn't work. I want to keep it simple and I don't want to have 100 other files doing something whereas I can just stick everything into a single file and manage just a single file as I really need a simple terraform to spin up one box. That's it. Simple as that. 

Thanks.

[Philip Nelson]

gah, apologies I hadn't read your initial question closely enough. Your example looks just like working versions I have. 

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[David Maze]

On Friday, May 5, 2017 at 9:10:47 AM UTC-4, Thorvald Hallvardsson wrote:

As you could clearly see from my first example I invoke user_data ... or rather I'm trying to invoke it from terraform. User_data is going to install whois during the bootstrap process. I can run remote-exec or even provision a file and then run remote-exec the thing is... I don't want to use SSH connection at all. By passing a data to user_data my 'script' runs from the cloud-init which doesn't require any SSH connection. It's the part of the booting process (or rather instance creation). 

Have you read through both the cloud-init documentation and source?  The documentation is pretty incomplete (which is frustrating given how important the "do things at boot time" capability is) but you can install packages using its YAML syntax; that's not necessarily better than running a shell script, but it might work better.

You can use the here-doc syntax pretty much anywhere, and if you're not interpolating anything into the template_file data you could just put it inline as the user_data field.  You can also use the template_cloudinit_multipart resource to wrap up MIME parts in a format cloud-init understands.  So I would probably write out:

user_data = "${data.template_cloudinit.multipart.user_data}"

data "template_cloudinit_multipart" "user_data" {

  part {

    content_type = "text/cloud-config"

    content = <<EOF

packages:

  - whois

EOF

  }

}

You might try adding the MIME wrapper with a `text/x-shellscript` type and seeing if it helps.  The documentation claims just having the shebang line is enough, but it's worth trying.

[Thorvald Hallvardsson]

Hi Dave,

Thanks for your input. If I would only have to install a single package :). I'm afraid that road leads to a dual carriage way and I really need to execute a bash script which does stuff... not just installing a package but does a lot of configuration bits and pieces before Ansible will run and do the rest. Installing whois was just a simple example to have a PoC that bash script can be executed as a 'line by line' script. 

I'm aware of the yaml format for cloud-init just didn't try it as it's not something I want. I know I can runcmd from cloud init but the syntax is so nasty... Anyway... I will have to try to work this around somehow.

Thank you!

[Philip Nelson]

As somebody else pointed out earlier the heredoc you have does appear to put space in front of the hashbang, #!/bin/bash. In most of our configurations we use data.template_file and a file rather than a heredoc. 

data "template_file" "user_data" {
  template = "${file("./somefile.sh.tpl")}"

  ...

}

probably makes more sense for you if it is going to be a real script

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[David Adams]

Thorvald,

Have you tried removing the indentation from the heredoc? I think that's worth a try, as in my experience I've had various issues with heredocs in Terraform and I've given up on trying to make them line up cleanly.

On Fri, May 5, 2017 at 9:08 AM, Philip Nelson <panman...@gmail.com> wrote:

As somebody else pointed out earlier the heredoc you have does appear to put space in front of the hashbang, #!/bin/bash. In most of our configurations we use data.template_file and a file rather than a heredoc. 

data "template_file" "user_data" {
  template = "${file("./somefile.sh.tpl")}"

  ...

}

probably makes more sense for you if it is going to be a real script

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