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How to use a cloud config file

When ordering a VPS, you can choose from one of four different installation options. One of the options available is to use a cloud config file.

With a cloud-config file you can automatically adjust the configuration of a Linux server after the installation process: During the first boot of your server, a program called cloud-init reads the data in the cloud-config file and adjusts the configuration based on this file to your wishes. For example, you can create users, set passwords, add SSH keys, add repositories, install packages and much more.

In this guide, we'll show you how to create and use a cloud config file when ordering a VPS. More general information about cloud init and cloud config can be found in this article.


Creating a cloud config file

 

The setup of a cloud config file is pretty self-explanatory if you have an example. In the steps below, we therefore emphasize examples of different use cases. Cloud-init supports multiple formats, but for this guide we use the YAML format.

  • We recommend configuring at least one user and an SSH key in your cloud config file and not putting sensitive information in your cloud config file.
     
  • All options in this section are optional and it is not necessary to use them all. For example, if you don't set up groups in your cloud-config file then only the default system groups and user groups are created.

Step 1

Start a text editor, such as Notepad, Notepad ++, Texteditor, or Gedit.


 

Step 2

The first line of a cloud config file should always be announced as such so that cloud-init can recognize it as a cloud config file. You do this by opening the file with the line:

# cloud-config

Then you add to the file the options that you want to adjust during the installation of your VPS. In this step we show this in the following parts:

Create groups
Create users: names, groups, passwords, ssh-keys
Change (root) password
Customize files
Execute first boot commands
Install packages
Remove automatically after installation

At the end of this section, we'll show what these options look like merged into your cloud-config file.

Create groups

#cloud-config
 groups:
 - Ubuntu: [root, sys]
 - cloud-users
Explanation

The syntax for creating groups is:

groups:
  # group with users
  - groupname1: [user1, user2, user3]
  # empty groep
  - groupname2

The code above  creates two groups: group name1 and group name2.

  • Groupname1 contains three users.
  • Groupname2 is empty.

System groups and users are automatically created during the installation process of your operating system.You do not have to create these separately and these options therefore mainly serve to create additional groups.

Create users

In the example below, we show some options that you can use when creating a user. In the explanation we show all available options. You are free to choose which of the available options you use.

#cloud-config
users:
  - name: transip
    groups: transip
    ssh_authorized_keys: 
      - ssh-rsa AAAAB3NzaC1yc2EAn64SJAF8cNUkV40EiUrsXJpu+MNtK2IXs9NDitR5V17cDZtqN+W3+8w== transip@voorbeeld.nl
      - ssh-rsa AAAAB3NzaC1ycMNtK2IXs9NDi64SJAF8cNUkV40EiUrsXJpu+MNtK2IXs17cDZtIXs17+8w== transip@voorbeeld.nl
    sudo: ['ALL=(ALL) NOPASSWD:ALL']
    shell: /bin/bash
Explanation
When creating users, always enter the name first and then the desired options, according to the following syntax:
#cloud-config
users:
- name: user1
  optie1: ...
  optie2: ...
- name: user2
  optie1: ...
  optie2: ...
  • name: the username
     
  • gecos: additional user information, for example the full name A. Non
     
  • primary_group: The user's primary group. By default, the primary group is automatically named after the user.
     
  • groups: additional groups in which the user is included. By default, new users are not added to additional groups.
     
  • selinux_user: the SELinux user for the user login. The default SELinux user is used if this option is not specified.
     
  • expiredate: the date (YYYY-MM-DD) on which the account expires.
     
  • ssh_import_id: the SSH ID imported from LaunchPad.
     
  • ssh_authorized_keys: A list of SSH keys that will be added to the user's authorized_keys file.
     
  • ssh_redirect_user: with the value true you block access via SSH keys (default: false).
     
  • lock_passwd: with the value false you block (SSH) login with a password (default: true).
     
  • passwd: the hash of the user's password. You can generate a password hash with the command:
    mkpasswd --method=SHA-512 --rounds=4096
    Note that for security reasons, cloud-init advises against entering the user's password in the cloud-init file, even if it has been hashed. It is safer to only provide an SSH key.
     
  • inactive: the value true creates the account as an inactive account (default: false).
     
  • no_create_home: the value true creates the user without a home directory in the / home / folder (default: false).
     
  • no_user_group: the value true creates the user without a group named after the user (default: false).
     
  • no_log_init: A value of true does not initialize the login databases (i.e. the log files) for the user (default: false).
     
  • sudo: set the user's sudo rights (default: none). Available options are:

        Full sudo access:
        sudo: ALL = (ALL) NOPASSWD: ALL
         
        Various sudo options:
        sudo:
          - ALL = (ALL) NOPASSWD: / bin / mysql
          - ALL = (ALL) ALL
         
        Disable Sudo access for the user:
        sudo: false

  • system: create the user as system user with the value true (default: false).
     
  • shell: the login shell for the created user (default: sh shell).

Default user

If you do not specify users, a user is automatically created in most operating systems. For example, in Ubuntu you get a user called 'ubuntu' with the legacy permissions (sudo without password, locked user, etc).

Do you want this 'ubuntu' user next to other user accounts? You create this by starting users: with -default, in other words:

users:
   - default
   - name: user 1
     option 1: ..
     option2: ..
   - name: user 2
     option 1: ..
     option2: ..

Adjusting the root password

The root password can be changed with the following syntax:

# cloud-config
chpasswd:
  list: |
    root: your password

It is also possible to enter passwords from other users, for example:

# cloud-config
chpasswd:
  list: |
    root: your password
    user1: another password

For security reasons, Cloud Init does not recommend modifying passwords via cloud config files.

Depending on your use case, it can be useful to configure an initial root password with chgpasswd during your installation. We recommend that you change the root password again after installing your server.


Customising files

There are two ways to modify files using a cloud config file:

  • You can completely overwrite a file via write_files and thus also change the owner or rights.
  • With runcmd you execute one or more commands, for example 'sed' commands to adjust specific rules.

The first is useful if you are modifying a small file, and the second for specific changes. To keep your cloud-config file clear, it is usually not desirable to modify large files with write_files.


write_files

Below is an example of how to change the configuration of / etc / ssh / sshd_config. For the readability of this article, the comments have been omitted from the file.

# cloud-config
write_files:
- path: / etc / ssh / sshd_config
  permissions: 0600
  owner: root: root
  content: |
       Port 12345

       HostKey / etc / ssh / ssh_host_rsa_key
       HostKey / etc / ssh / ssh_host_ecdsa_key
       HostKey / etc / ssh / ssh_host_ed25519_key

       SyslogFacility AUTHPRIV

       PermitRootLogin No

       AuthorizedKeysFile .ssh / authorized_keys

       PasswordAuthentication no

       ChallengeResponseAuthentication no

       GSSAPIAuthentication yes
       GSSAPICleanupCredentials no

       UsePAM yes

       X11 Forwarding yes

       AcceptEnv LONG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
       AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
       AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
       AcceptEnv XMODIFIERS

       Subsystem sftp / usr / libexec / openssh / sftp server
Explanation

Write_files allows you to overwrite or create a complete file. The syntax as seen in the example above is:

# cloud-config
write_files:
  - path: / folder / subfolder / filename
    permissions: XXXX
    owner: user: group
    content: |
         line 1 ...
         line 2 ...
 - path: / folder1 / subfolder1 / filename1
   content: |
        line 1 ...
        line 2 ...
  • After path you indicate which file is in which folder.
  • Permissions is optional and can be used to change chmod permissions.
  • Owner is optional and can be used to change the owner of a file.
  • The pipe | character behind content: indicates that a list follows. In this case, this is a list of all the lines to be written to the file.

Run first boot commands with runcmd

Runcmd is a powerful tool to execute first boot commands (i.e. these are only executed the first time ever you start VPS). In the example below we show how to edit the contents of a file with a sed command (here the SSH port in the ssh configuration), but you can use runcmd for any command.

# cloud-config
runcmd:
  - sed -i -e '/^Port/s/^.*$/Port 12345 /' / etc / ssh / sshd_config
Runcmd syntax

Runcmd is used by first addressing runcmd: and then introducing the command with a dash on a new line.

If you want to run multiple commands with runcmd, you place each command on a new line.

# cloud-config
runcmd:
  - command 1
  - command 2

Install packages

With a cloud config file you can very easily install specific packages during your installation. For this you use the syntax:

# cloud-config
packages:
 - package name 1
 - package name 2
 - etc

Remove automatically after installation

We recommend not putting sensitive information in the config. Your cloud-config data is always accessible from your VPS via http://pxe.frontend.transip.nl/cloudinit/user-data. You can solve this by adding the code below; this will remove your cloud-config data from the above address after installation.

phone_home:
  url: http://pxe.frontend.transip.nl/cloudinit/post-install
  post: []
  tries: 5

Alternatively, you can block 37.97.254.100 in your firewall.


Putting everything together

Above you have seen a lot of options that you can use in a cloud config file. If you put them all together, your file will look like this:

# cloud-config
groups:
  - Ubuntu: [root, sys]
  - cloud users
users:
  - name: transip
    groups: transip
    ssh_authorized_keys:
      - ssh-rsa AAAAB3NzaC1yc2EAn64SJAF8cNUkV40EiUrsXJpu + MNtK2IXs9NDitR5V17cDZtqN + W3 + 8w == transip@example.com
      - ssh-rsa AAAAB3NzaC1ycMNtK2IXs9NDi64SJAF8cNUkV40EiUrsXJpu + MNtK2IXs17cDZtIXs17 + 8w == transip@example.com
    sudo: ['ALL = (ALL) NOPASSWD: ALL']
    shell: / bin / bash
chpasswd:
  list: |
    root: your password
write_files:
- path: / etc / ssh / sshd_config
  permissions: 0600
  owner: root: root
  content: |
    Port 12345

    HostKey / etc / ssh / ssh_host_rsa_key
    HostKey / etc / ssh / ssh_host_ecdsa_key
    HostKey / etc / ssh / ssh_host_ed25519_key

    SyslogFacility AUTHPRIV

    PermitRootLogin No

    AuthorizedKeysFile      .ssh/authorized_keys

    PasswordAuthentication no

    ChallengeResponseAuthentication no

    GSSAPIAuthentication yes
    GSSAPICleanupCredentials no

    UsePAM yes

    X11Forwarding yes

    AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
    AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
    AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
    AcceptEnv XMODIFIERS

    Subsystem       sftp    /usr/libexec/openssh/sftp-server

runcmd: 
  - sed -i -e '/^Port/s/^.*$/Port 12345/' /etc/ssh/sshd_config

packages:
 - packagename1
 - packagename2

phone_home:
  url: http://pxe.frontend.transip.nl/cloudinit/post-install
  post: []
  tries: 5

 

Step 3

Save your cloud config file, for example with the name cloud-config.yaml. You can then use your cloud config file, for example using our API or when ordering a VPS.


Using your cloud config file when ordering a VPS

 

Step 1

When ordering a VPS, after choosing the specifications and operating system if you are logged in to your TransIP account, there are 2 options:

  • If you haven't added an SSH-key yet, you're shown an option to enter your SSH key as shown below
    vps fast installs add ssh key
  • If you have added aan SSH key before, you can either select it, or add a new one.
    fast installs add ssh key other method

If you are not logged in, you will see the option for a one-time password:

vps fast installs one time password - choose other installation method

Whichever is the case, click on 'Choose another installation method'.


 

Step 2

You will now be given the choice to choose an installation method, as in the screenshot below. Select 'Install via cloud-config user data'.

fast install methods cloud config


 

Step 3

You will now see the 'Install via cloud-config user data' screen. Copy and paste the contents of your cloud config file, as shown in the screenshot below.

vps fast installs cloud config data

Your cloud config data is now applied. You will receive a confirmation of your order by e-mail with a feedback on whether your cloud config configuration could be successfully applied.


 

This brings us to the end of this article. Are you looking for even more options such as adding repositories? Then take a look at cloud-init's documentation.

If you have any questions regarding this article, do not hesitate to contact our support department. You can reach them via the 'Contact us' button at the bottom of this page.

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