Templates

Templates

Templates are written in Terraform and describe the infrastructure for workspaces (e.g., docker_container, aws_instance, kubernetes_pod).

In most cases, a small group of users (team leads or Coder administrators) have permissions to create and manage templates. Then, other users provision their workspaces from templates using the UI or CLI.

Get the CLI

The CLI and the server are the same binary. We did this to encourage virality so individuals can start their own Coder deployments.

From your local machine, download the CLI for your operating system from the releases or run:

curl -fsSL https://coder.com/install.sh | sh

To see the sub-commands for managing templates, run:

coder templates --help

Before you can create templates, you must first login to your Coder deployment with the CLI.

coder login https://coder.example.com # aka the URL to your coder instance

This will open a browser and ask you to authenticate to your Coder deployment, returning an API Key.

Make a note of the API Key. You can re-use the API Key in future CLI logins or sessions.

coder --token <your-api-key> login https://coder.example.com/ # aka the URL to your coder instance

Add a template

Before users can create workspaces, you'll need at least one template in Coder.

# create a local directory to store templates
mkdir -p $HOME/coder/templates
cd $HOME/coder/templates

# start from an example
coder templates init

# optional: modify the template
vim <template-name>/main.tf

# add the template to Coder deployment
coder templates create <template-name>

See the documentation and source code for each example as well as community templates in the examples/ directory in the repo.

Configure Max Workspace Autostop

To control cost, specify a maximum time to live flag for a template in hours or minutes.

coder templates create my-template --default-ttl 4h

Customize templates

Example templates are not designed to support every use (e.g examples/aws-linux does not support custom VPCs). You can add these features by editing the Terraform code once you run coder templates init (new) or coder templates pull (existing).

Refer to the following resources to build your own templates:

Terraform: Documentation and Registry
Common concepts in templates and Coder Terraform provider
Coder example templates code

Concepts in templates

While templates are written with standard Terraform, the Coder Terraform Provider is used to define the workspace lifecycle and establish a connection from resources to Coder.

Below is an overview of some key concepts in templates (and workspaces). For all template options, reference Coder Terraform provider docs.

Resource

Resources in Coder are simply Terraform resources. If a Coder agent is attached to a resource, users can connect directly to the resource over SSH or web apps.

Coder agent

Once a Coder workspace is created, the Coder agent establishes a connection between a resource (docker_container) and Coder, so that a user can connect to their workspace from the web UI or CLI. A template can have multiple agents to allow users to connect to multiple resources in their workspace.

Resources must download and start the Coder agent binary to connect to Coder. This means the resource must be able to reach your Coder URL.

data "coder_workspace" "me" {
}

resource "coder_agent" "pod1" {
  os   = "linux"
  arch = "amd64"
}

resource "kubernetes_pod" "pod1" {
  spec {
    ...
    container {
      command = ["sh", "-c", coder_agent.pod1.init_script]
      env {
        name  = "CODER_AGENT_TOKEN"
        value = coder_agent.dev.token
      }
    }
  }
}

The coder_agent resource can be configured with additional arguments. For example, you can use the env property to set environment variables that will be inherited by all child processes of the agent, including SSH sessions. See the Coder Terraform Provider documentation for the full list of supported arguments for the coder_agent.

`startup_script`

Use the Coder agent's startup_script to run additional commands like installing IDEs, cloning dotfiles, and cloning project repos.

Note: By default, the startup script is executed in the background. This allows users to access the workspace before the script completes. If you want to change this, see startup_script_behavior below.

Here are a few guidelines for writing a good startup script (more on these below):

Use set -e to exit the script if any command fails and || true for commands that are allowed to fail
Use & to start a process in the background, allowing the startup script to complete
Inform the user about what's going on via echo

resource "coder_agent" "coder" {
  os   = "linux"
  arch = "amd64"
  dir = "/home/coder"
  startup_script = <<EOT
#!/bin/bash

# Install code-server 4.8.3 under /tmp/code-server using the "standalone" installation
# that does not require root permissions. Note that /tmp may be mounted in tmpfs which
# can lead to increased RAM usage. To avoid this, you can pre-install code-server inside
# the Docker image or VM image.
echo "Installing code-server..."
curl -fsSL https://code-server.dev/install.sh | sh -s -- --method=standalone --prefix=/tmp/code-server --version 4.8.3

# The & prevents the startup_script from blocking so the next commands can run.
# The stdout and stderr of code-server is redirected to /tmp/code-server.log.
echo "Starting code-server..."
/tmp/code-server/bin/code-server --auth none --port 13337 >/tmp/code-server.log 2>&1 &

# Notice: var.repo and var.dotfiles_uri are specified elsewhere in the Terraform
# code as input variables.
REPO=${var.repo}
DOTFILES_URI=${var.dotfiles_uri}

# clone repo
ssh-keyscan -t rsa github.com >> ~/.ssh/known_hosts
echo "Cloning $REPO..."
git clone --progress [email protected]:"$REPO"

# use coder CLI to clone and install dotfiles
echo "Cloning dotfiles..."
coder dotfiles -y "$DOTFILES_URI"
  EOT
}

The startup script can contain important steps that must be executed successfully so that the workspace is in a usable state, for this reason we recommend using set -e (exit on error) at the top and || true (allow command to fail) to ensure the user is notified when something goes wrong. These are not shown in the example above because, while useful, they need to be used with care. For more assurance, you can utilize shellcheck to find bugs in the script and employ set -euo pipefail to exit on error, unset variables, and fail on pipe errors.

We also recommend that startup scripts do not run forever. Long-running processes, like code-server, should be run in the background. This is usually achieved by adding & to the end of the command. For example, sleep 10 & will run the command in the background and allow the startup script to complete.

Note: If a backgrounded command (&) writes to stdout or stderr, the startup script will not complete until the command completes or closes the file descriptors. To avoid this, you can redirect the stdout and stderr to a file. For example, sleep 10 >/dev/null 2>&1 & will redirect the stdout and stderr to /dev/null (discard) and run the command in the background.

PS. Notice how each step starts with echo "..." to provide feedback to the user about what is happening? This is especially useful when the startup script behavior is set to blocking because the user will be informed about why they're waiting to access their workspace.

`startup_script_behavior`

Use the Coder agent's startup_script_behavior to change the behavior between blocking and non-blocking (default). The blocking behavior is recommended for most use cases because it allows the startup script to complete before the user accesses the workspace. For example, let's say you want to check out a very large repo in the startup script. If the startup script is non-blocking, the user may log in via SSH or open the IDE before the repo is fully checked out. This can lead to a poor user experience.

resource "coder_agent" "coder" {
  os   = "linux"
  arch = "amd64"
  startup_script_behavior = "blocking"
  startup_script = "echo 'Starting...'"

Whichever behavior is enabled, the user can still choose to override it by specifying the appropriate flags (or environment variables) in the CLI when connecting to the workspace. The behavior can be overridden by one of the following means:

Set an environment variable (for use with ssh or coder ssh):
- export CODER_SSH_WAIT=yes (blocking)
- export CODER_SSH_WAIT=no (non-blocking)
Use a flag with coder ssh:
- coder ssh --wait=yes my-workspace (blocking)
- coder ssh --wait=no my-workspace (non-blocking)
Use a flag to configure all future ssh connections:
- coder config-ssh --wait=yes (blocking)
- coder config-ssh --wait=no (non-blocking)

Start/stop

Learn about resource persistence in Coder

Coder workspaces can be started/stopped. This is often used to save on cloud costs or enforce ephemeral workflows. When a workspace is started or stopped, the Coder server runs an additional terraform apply, informing the Coder provider that the workspace has a new transition state.

This template sample has one persistent resource (docker volume) and one ephemeral resource (docker container).

data "coder_workspace" "me" {
}

resource "docker_volume" "home_volume" {
  # persistent resource (remains a workspace is stopped)
  count = 1
  name  = "coder-${data.coder_workspace.me.id}-home"
  lifecycle {
    ignore_changes = all
  }
}

resource "docker_container" "workspace" {
  # ephemeral resource (deleted when workspace is stopped, created when started)
  count = data.coder_workspace.me.start_count # 0 (stopped), 1 (started)
  volumes {
    container_path = "/home/coder/"
    volume_name    = docker_volume.home_volume.name
    read_only      = false
  }
  # ... other config
}

Using updated images when rebuilding a workspace

To ensure that Coder uses an updated image when rebuilding a workspace, we suggest that admins update the tag in the template (e.g., my-image:v0.4.2 -> my-image:v0.4.3) or digest (my-image@sha256:[digest] -> my-image@sha256:[new_digest]).

Alternatively, if you're willing to wait for longer start times from Coder, you can set the imagePullPolicy to Always in your Terraform template; when set, Coder will check image:tag on every build and update if necessary:

resource "kubernetes_pod" "podName" {
    spec {
        container {
            image_pull_policy = "Always"
        }
    }
}

Edit templates

You can edit a template using the coder CLI or the UI. Only template admins and owners can edit a template.

Using the UI, navigate to the template page, click on the menu, and select "Edit files". In the template editor, you create, edit and remove files. Before publishing a new template version, you can test your modifications by clicking the "Build template" button. Newly published template versions automatically become the default version selection when creating a workspace.

Tip: Even without publishing a version as active, you can still use it to create a workspace before making it the default for everybody in your organization. This may help you debug new changes without impacting others.

Using the CLI, login to Coder and run the following command to edit a single template:

coder templates edit <template-name> --description "This is my template"

Review editable template properties by running coder templates edit -h.

Alternatively, you can pull down the template as a tape archive (.tar) to your current directory:

coder templates pull <template-name> file.tar

Then, extract it by running:

tar -xf file.tar

Make the changes to your template then run this command from the root of the template folder:

coder templates push <template-name>

Your updated template will now be available. Outdated workspaces will have a prompt in the dashboard to update.

Delete templates

You can delete a template using both the coder CLI and UI. Only template admins and owners can delete a template, and the template must not have any running workspaces associated to it.

Using the CLI, login to Coder and run the following command to delete a template:

coder templates delete <template-name>

In the UI, navigate to the template you want to delete, and select the dropdown in the right-hand corner of the page to delete the template.

Delete workspaces

When a workspace is deleted, the Coder server essentially runs a terraform destroy to remove all resources associated with the workspace.

Terraform's prevent-destroy and ignore-changes meta-arguments can be used to prevent accidental data loss.

Coder apps

By default, all templates allow developers to connect over SSH and a web terminal. See Configuring Web IDEs to learn how to give users access to additional web applications.

Template administrators can hide apps like the web-based Terminal or VS Code Desktop with the display_apps configuration in the coder_agent resource. For example, the following configuration block will hide all default Coder apps except the web terminal.

  display_apps {
    vscode = false
    vscode_insiders = false
    ssh_helper = false
    port_forwarding_helper = false
    web_terminal = true
  }

Example use cases for display_apps are JetBrains users or zero-trust deployments who do not want nor should have access to a local VS Code IDE.

Data source

When a workspace is being started or stopped, the coder_workspace data source provides some useful parameters. See the Coder Terraform provider for more information.

For example, the Docker quick-start template sets a few environment variables based on the username and email address of the workspace's owner, so that you can make Git commits immediately without any manual configuration:

resource "coder_agent" "main" {
  # ...
  env = {
    GIT_AUTHOR_NAME = "${data.coder_workspace.me.owner}"
    GIT_COMMITTER_NAME = "${data.coder_workspace.me.owner}"
    GIT_AUTHOR_EMAIL = "${data.coder_workspace.me.owner_email}"
    GIT_COMMITTER_EMAIL = "${data.coder_workspace.me.owner_email}"
  }
}

You can add these environment variable definitions to your own templates, or customize them however you like.

Troubleshooting templates

Occasionally, you may run into scenarios where a workspace is created, but the agent is either not connected or the startup script has failed or timed out.

Agent connection issues

If the agent is not connected, it means the agent or init script has failed on the resource.

$ coder ssh myworkspace
⢄⡱ Waiting for connection from [agent]...

While troubleshooting steps vary by resource, here are some general best practices:

Ensure the resource has curl installed (alternatively, wget or busybox)
Ensure the resource can curl your Coder access URL
Manually connect to the resource and check the agent logs (e.g., kubectl exec, docker exec or AWS console)
- The Coder agent logs are typically stored in /tmp/coder-agent.log
- The Coder agent startup script logs are typically stored in /tmp/coder-startup-script.log
- The Coder agent shutdown script logs are typically stored in /tmp/coder-shutdown-script.log
This can also happen if the websockets are not being forwarded correctly when running Coder behind a reverse proxy. Read our reverse-proxy docs

Startup script issues

Depending on the contents of the startup script, and whether or not the startup script behavior is set to blocking or non-blocking, you may notice issues related to the startup script. In this section we will cover common scenarios and how to resolve them.

Unable to access workspace, startup script is still running

If you're trying to access your workspace and are unable to because the startup script is still running, it means the startup script behavior option is set to blocking or you have enabled the --wait=yes option (for e.g. coder ssh or coder config-ssh). In such an event, you can always access the workspace by using the web terminal, or via SSH using the --wait=no option. If the startup script is running longer than it should, or never completing, you can try to debug the startup script to resolve the issue. Alternatively, you can try to force the startup script to exit by terminating processes started by it or terminating the startup script itself (on Linux, ps and kill are useful tools).

For tips on how to write a startup script that doesn't run forever, see the startup_script section. For more ways to override the startup script behavior, see the startup_script_behavior section.

Template authors can also set the startup script behavior option to non-blocking, which will allow users to access the workspace while the startup script is still running. Note that the workspace must be updated after changing this option.

Your workspace may be incomplete

If you see a warning that your workspace may be incomplete, it means you should be aware that programs, files, or settings may be missing from your workspace. This can happen if the startup script is still running or has exited with a non-zero status (see startup script error). No action is necessary, but you may want to start a new shell session after it has completed or check the startup script logs to see if there are any issues.

Session was started before the startup script finished

The web terminal may show this message if it was started before the startup script finished, but the startup script has since finished. This message can safely be dismissed, however, be aware that your preferred shell or dotfiles may not yet be activated for this shell session. You can either start a new session or source your dotfiles manually. Note that starting a new session means that commands running in the terminal will be terminated and you may lose unsaved work.

Examples for activating your preferred shell or sourcing your dotfiles:

exec zsh -l
source ~/.bashrc

Startup script exited with an error

When the startup script exits with an error, it means the last command run by the script failed. When set -e is used, this means that any failing command will immediately exit the script and the remaining commands will not be executed. This also means that your workspace may be incomplete. If you see this error, you can check the startup script logs to figure out what the issue is.

Common causes for startup script errors:

A missing command or file
A command that fails due to missing permissions
Network issues (e.g., unable to reach a server)

Debugging the startup script

The simplest way to debug the startup script is to open the workspace in the Coder dashboard and click "Show startup log" (if not already visible). This will show all the output from the script. Another option is to view the log file inside the workspace (usually /tmp/coder-startup-script.log). If the logs don't indicate what's going on or going wrong, you can increase verbosity by adding set -x to the top of the startup script (note that this will show all commands run and may output sensitive information). Alternatively, you can add echo statements to show what's going on.

Here's a short example of an informative startup script:

echo "Running startup script..."
echo "Run: long-running-command"
/path/to/long-running-command
status=$?
echo "Done: long-running-command, exit status: ${status}"
if [ $status -ne 0 ]; then
  echo "Startup script failed, exiting..."
  exit $status
fi

Note: We don't use set -x here because we're manually echoing the commands. This protects against sensitive information being shown in the log.

This script tells us what command is being run and what the exit status is. If the exit status is non-zero, it means the command failed and we exit the script. Since we are manually checking the exit status here, we don't need set -e at the top of the script to exit on error.