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Installing and Configuring cloud-init in Linux

Installing and Configuring cloud-init in Linux
Hostman Team
Technical writer
Linux
26.09.2024
Reading time: 10 min

cloud-init is a free and open-source package designed for configuring Linux-based virtual machines during their startup.

In a traditional (home) environment, we would install systems from a CD or USB drive and manually configure them via a standard installer. However, in a cloud environment, we may need to configure systems regularly and frequently create, delete, and restart instances. In such cases, manual configuration becomes impractical and unfeasible.

cloud-init automates the configuration process and standardizes the setup of virtual machines.

What Is cloud-init

The main task of cloud-init is to process input metadata (such as user data) and configure the virtual machine before it starts. This allows us to pre-configure servers, install software, prepare working directories, and create users with specific permissions.

Cloud-init and Hostman Cloud Servers

Hostman cloud servers support working with cloud-init scripts through the control panel. Hostman’s documentation includes a brief guide on using cloud-init scripts directly on their cloud servers. Essentially, Hostman offers a text editor for cloud-init scripts accessible via a web browser, allowing users to pass configuration data directly to the utility before the system starts.

Installing Cloud-init

There are several ways to get a Linux OS with cloud-init:

  • Use a specialized Linux OS image with pre-installed cloud-init (we’ll mention some key examples below).

  • Use pre-built distributions from cloud providers (most cloud platforms support cloud-init, though the setup processes may vary).

  • Build a custom OS image using HashiCorp Packer.

  • Manually install the cloud-init package.

Cloud-init Images

  • Ubuntu: The most common cloud-init image is Ubuntu 22.04 Cloud Images, officially created by Canonical for public cloud use. These images are optimized and tailored for cloud tasks.

  • Debian: Similarly, Debian Cloud offers specialized cloud images for Debian users.

  • Alma Linux: Another distribution designed for cloud deployment is Alma Linux Cloud.

  • VMware: VMware’s Photon image, built for cloud environments, also comes with pre-installed cloud-init.

Alternatively, you can install cloud-init manually.

Installation via APT

In most Linux distributions, cloud-init is installed like any other package and includes three systemd services located in the /lib/systemd/system/ directory:

  • cloud-init.service

  • cloud-config.service

  • cloud-final.service

Additionally, there are two more auxiliary systemd services:

  • cloud-init-local.service

  • cloud-init-hotplugd.service

Before installing, it's best to update the list of available repositories:

sudo apt update

Then, download the cloud-init package via APT:

sudo apt install cloud-init

In some Linux images, cloud-init may already be installed by default. If so, the system will notify you after running the install command.

cloud-init also supports additional modules that expand configuration capabilities. The full list of modules is available in the official documentation.

Running cloud-init

Since cloud-init operates as a service, it starts immediately after the systemd utility starts, i.e., when the physical machine starts and before the system connects to the network. This allows for pre-configuring network settings, gateways, DNS addresses, etc.

Cloud-init Workflow

There are three main stages in cloud-init’s workflow, during which the system is configured. Each stage triggers specific cloud-init services:

  1. Before networking (init): Initial setup before the network starts, including system settings, network configurations, and disk preparation.

    • cloud-init-local.service

    • cloud-init.service

  2. After networking (config): Network is available, so updates and required packages are installed.

    • cloud-config.service

  3. Final stage (final): Final configurations, such as user creation and permission assignments, are applied.

    • cloud-final.service

    • cloud-init-hotplugd.service

Cloud-init Modules

cloud-init offers additional modules that enhance system configuration. These modules run in sequence at various stages. Depending on the specific use case, they can be triggered during any of the three stages. Module execution is managed through three lists in the configuration file:

  • cloud_init_modules: Modules run during the initialization (init) stage before the network starts.

  • cloud_config_modules: Modules run during the configuration (cloud) stage after the network is up.

  • cloud_final_modules: Modules run during the final stage.

In more detail, cloud-init’s stages can be broken down into five steps:

  1. systemd checks if cloud-init needs to run during system boot.

  2. cloud-init starts, locates local data sources, and applies the configurations. At this stage, the network is configured.

  3. During the initial setup, cloud-init processes user data and runs the modules listed under cloud_init_modules in the configuration file.

  4. During the configuration phase, cloud-init runs the modules listed under cloud_config_modules.

  5. In the final stage, cloud-init runs the modules from cloud_final_modules, installing the specified packages.

You can find more details on the cloud-init workflow in the official documentation.

Each module also has an additional parameter that specifies how often the module runs during system configuration:

  • per instance: The module runs each time a new system instance (clone or snapshot) boots.

  • per once: The module runs only once during the initial system boot.

  • per always: The module runs at every system startup.

Cloud-init Configuration

In public (AWS, GCP, Azure, Hostman) or private clouds (OpenStack, CloudStack), a service usually provides the virtual machine with environment data. cloud-init uses these data in a specific order:

  • User data (user-data): Configurations and directives defined in the cloud.cfg file. These may include files to run, packages to install, and shell scripts. Typically, user-data configure specific virtual machine instances.

  • Metadata (meta-data): Environment information, such as the server name or instance ID, used after user-data.

  • Vendor data (vendor-data): Information from cloud service providers, used for default settings, applied after metadata.

Metadata is often available at a URL like http://localhost/latest/meta-data/, and user data at http://localhost/latest/user-data/.

Cloud-init Scripts

When the system boots, cloud-init first checks the YAML configuration files with the scripts and then executes the instructions. YAML is a format for data serialization that looks like markup but is not.

The primary YAML configuration file for cloud-init is located at /etc/cloud/cloud.cfg. This file serves as the main configuration script, with directives and parameters for specific cloud-init modules.

You can write scripts as YAML files (using #cloud-config) or as shell scripts (using #!/bin/sh).

Here’s a simple example of a cloud-init script setting a hostname:

#cloud-config
hostname: my-host
fqdn: my-address.com
manage_etc_hosts: true

In this example:

  • #cloud-config: indicates that the instructions are for cloud-init in YAML format.

  • hostname: sets the short hostname.

  • fqdn: sets the fully qualified domain name.

  • manage_etc_hosts: allows cloud-init to manage the /etc/hosts file.

If this option is set to false, cloud-init won’t overwrite manual changes to /etc/hosts on reboot.

Cloud-init Script Examples

Cloud-init configuration using YAML should start with #cloud-config.

Users and Groups

When a virtual machine starts, you can predefine users with the users directive:

#cloud-config
users:
  - name: userOne
    gecos: This is the first user
    groups: sudo
    shell: sh
    system: true

  - name: userTwo
    gecos: This is the second user
    groups: sudo
    shell: /bin/bash
    system: false
    expiredate: '2030-01-02'

As shown, each new user entry begins with a dash, and parameters are specified in a "key: value" format.

These parameters mean:

  • name: User account name

  • gecos: Brief info about the user

  • groups: Groups the user belongs to

  • shell: Default shell for the user, here set to the simplest sh.

  • system: If true, the account will be a system account without a home directory.

  • expiredate: The user's expiration date in the "YYYY-MM-DD" format.

Changing User Passwords

Another simple directive is chpasswd, used to reset an existing user's password. Example configuration:

#cloud-config
chpasswd:
  list: |
    userOne:passOne
    userTwo:passTwo
    userThree:passThree
  expire: false

This sets a list of users and their new passwords. The | symbol indicates a multi-line entry. The expire parameter defines whether the password will need to be changed after expiration.

Updating the Repository List

cloud-config has a directive for updating the available package list: package_update. It's the declarative equivalent of running

 sudo apt update 

By default, it's set to true, meaning cloud-init will always update the package list unless explicitly disabled:

#cloud-config
package_update: false

Installing Specific Packages

For updating or installing specific packages, use the packages directive:

#cloud-config
packages:
  - nginx
  - nodejs

Running Commands

The runcmd directive allows you to execute console commands through cloud-config. Simply pass a list of commands that cloud-init will run in sequence:

#cloud-config
runcmd:
  - echo 'This is a string command!' >> /somefile.txt
  - [ sh, -c, "echo 'This is a list command!' >> /somefile.txt" ]

Here, two types of commands are used:

  1. As a simple string.

  2. As a YAML list specifying the executable and its arguments.

Another similar directive is bootcmd. While runcmd runs commands only on the system's first boot, bootcmd runs commands on every boot:

#cloud-config
bootcmd:
  - echo 'Command that runs at every system boot!'

Creating and Running a Script

You can combine runcmd with the write_files directive to create and run a script:

#cloud-config
write_files:
  - path: /run/scripts/somescript.sh
    content: |
      #!/bin/bash
      echo 'This script just executed!'
    permissions: '0755'
runcmd:
  - [ sh, "/run/scripts/somescript.sh" ]

The permissions parameter (set to 0755) means the script is readable and executable by all, but only writable by the owner.

Overriding Module Execution

You can override the list of modules to be executed at specific configuration stages. For example, the default cloud_config_modules list might look like this:

#cloud-config
cloud_config_modules:
  - emit_upstart
  - snap
  - ssh-import-id
  - locale
  - set-passwords
  - grub-dpkg
  - apt-pipelining
  - apt-configure
  - ubuntu-advantage
  - ntp
  - timezone
  - disable-ec2-metadata
  - runcmd
  - byobu

Remember, there are three stages:

  • cloud_init_modules

  • cloud_config_modules

  • cloud_final_modules

If you remove runcmd, for example, the commands within it won’t execute.

Updating Repositories and Installing Packages via Shell Script

cloud-init configurations can also consist purely of shell scripts. In this case, the script starts with #!/bin/sh instead of #cloud-config:

#!/bin/sh
apt update
apt -y install nodejs
apt -y install nginx

The -y flag automatically answers "yes" to any prompts during installation.

Conclusion

In this guide, we covered the theoretical and practical aspects of using cloud-init:

  • How cloud-init works.

  • How to interact with cloud-init for system configuration.

  • Writing scripts in YAML or shell format.

  • Example configurations.

cloud-init runs before the system boots, ensuring that the instance follows the desired configuration (network, directories, packages, updates). cloud-init uses modules for specific configuration tasks, and the system configuration is done in phases:

  • init (before networking)

  • config (after networking)

  • final (last stage)

More detailed information is available in the official documentation maintained by Canonical, the primary developer of Ubuntu.

Linux
26.09.2024
Reading time: 10 min

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Changer Device: Refers to the device tied to the autochanger, typically for physical devices. Device Block: Name: Identifier for the device. Media Type: Media type associated with the device. Must match the Pool block media type. Archive Device: Full path to the device or directory for storing backups; /srv/backup in this case. LabelMedia: Whether Bacula should auto-label new media. Random Access: Whether random access is supported. AutomaticMount: Whether to auto-mount the device when used. RemovableMedia: Specifies if the media is removable. AlwaysOpen: Whether the device should always stay open. Maximum Concurrent Jobs: Maximum number of simultaneous jobs using this device. Since we previously specified the directory for backup storage, create it: mkdir -p /srv/backup Set the ownership to the bacula user: chown bacula:bacula /srv/backup Next, check the config file for syntax errors: /usr/sbin/bacula-sd -t -c /etc/bacula/bacula-sd.conf If there are no syntax errors, the output will be empty. Otherwise, it will indicate the line number and description of any error. Restart the storage daemon: systemctl restart bacula-sd Creating a Backup Backups in Bacula are created using the bconsole command-line tool. Launch the utility: bconsole If it connects to the Director component successfully, it will display 1000 OK. Before running a backup, you can check the status of all components by entering the command: status This will display a list of the five Bacula system components. To check them all, enter 6. To initiate a backup, enter the command: run From the list, choose the BackupClient1 option (your client name might differ based on previous config), by typing 1. After selecting the option, you’ll see detailed info about the backup operation. You’ll then be prompted with three choices: yes — start the backup process; mod — modify parameters before starting; no — cancel the backup. If you enter mod, you’ll be able to edit up to 9 parameters. To proceed with the backup, type yes. To view all backup and restore jobs and their statuses: list jobs In our case, a backup with Job ID 1 was created: list jobid=1 If the status is T, the backup was successful. Possible statuses in the "Terminated Jobs" column: T (Success) — Job completed successfully. E (Error) — Job ended with an error. A (Canceled) — Job was canceled by the user. F (Fatal) — Job ended due to a critical error. R (Running) → Terminated — Job completed (may be successful or not). You can also monitor backup activity and errors via the log file: cat /var/log/bacula/bacula.log Once the backup finishes, the file will be saved in the specified directory. file Vol-0001 Restoring Files from Backup Earlier, we backed up the /root/test_backups directory, which contained six .txt files. Suppose these files were lost or deleted. Let’s restore them: Launch the Bacula console: bconsole Start the restore process: restore You’ll see 12 available restore options. We’ll use option 3. Type 3. Earlier we used Job ID 1 for our backup. Enter 1.  You’ll enter a file selection mode. Since our files were in the root/test_backups directory, navigate there. All previously saved files should be visible. To restore the whole directory, go up one level: cd .. Then mark the whole test_backups folder: mark test_backups/ Finish selection: done The system will display a final summary showing which data will be restored and the target directory (in our case: /root/restored-files). To start the restore, enter yes. Finally, verify that the files have been successfully restored. Conclusion We’ve now reviewed the installation and configuration of Bacula, a client-server backup solution. Bacula isn’t limited to backing up regular files—thanks to its plugin support, it can also handle backups of virtual machines, OS images, and more.
18 July 2025 · 14 min to read
Linux

Installing Arch Linux in a Cloud Environment

Arch Linux is a lightweight and flexible Linux distribution that provides users with extensive opportunities for customizing and optimizing their systems. It includes a minimal amount of preinstalled software and offers a console-based interface. In most cases, it is used by experienced users: professional developers, system administrators, or hackers. This is due to the complexity of its installation and subsequent configuration, which involves adding the required packages and components to the system. However, these difficulties are justified, because in the end the user gets exactly the system and services they need. In this article, we will explain how to install Arch Linux on your cloud server and perform its basic configuration. Advantages of Arch Linux It is worth noting that Arch Linux is ideally suited as an OS for a cloud server due to its low resource requirements. This distribution also has several other advantages: System UpdatesArch Linux updates automatically when a new OS version is released. Software InstallationPackages can be downloaded both over the network and from a local disk. In addition, the installed software does not need to be specifically compatible with Arch Linux. Rich RepositoriesArch Linux offers a wide variety of packages. Today, there are over 12,000 packages in the official repositories alone. In the community repository, there are even more — over 83,000. Up-to-date DocumentationThe official Arch Linux documentation is actively updated to reflect the latest changes and innovations. This ensures accurate and relevant system information. Active CommunityThis distribution has an active user community ready to help and share their experience. There are many forums, wikis, and repositories where you can find detailed instructions and guides for installation, configuration, and troubleshooting. 1. Preparing for Installation To follow this guide and install Arch Linux, you will need: A cloud server with any operating system (in our case, Debian 11); A link to the Arch Linux image from an official source; An additional disk, which you can attach under the Plan tab in the control panel. Step 1. To install Arch Linux on the server, you must first upload its installation image from an official source in .iso format. For example: wget https://mirror.rackspace.com/archlinux/iso/2025.06.01/archlinux-2025.06.01-x86_64.iso Step 2. Next, add a new disk where the installation image will be stored. It will appear in the system as /dev/sdb. You can specify the minimum disk size. Step 3. Write the installation image to the new disk: dd if=archlinux-2025.06.01-x86_64.iso of=/dev/sdb The writing process will take some time. When finished, verify it with the following command: fdisk -l In the output, you will see that the installation image has been written to the new disk, creating two necessary partitions. Step 4. After writing the installation image, proceed to boot from it. To do this, go to the Access tab and boot the server from the recovery disk. Open the console in the control panel.  Step 5. In the console window, go to the Boot existing OS menu item and press Tab on your keyboard. This will allow you to edit the text at the bottom of the screen. Here, you need to manually replace hd0 with hd1, as shown in the figure below. After that, press Enter to launch the installation program. Step 6. In the system bootloader that appears, select the first option. 2. Partitioning the Disk Now we can partition the main disk (sda). In our case, there will be 3 partitions: a 300 MB UEFI partition (type EFI), a 700 MB swap partition (type Linux swap), and a main filesystem partition taking up all remaining space (type Linux). In your own installation, the number and size of partitions may differ depending on your requirements. Make sure there are no important files on the server’s disk, because it will be formatted later. You may also wish to back it up to preserve important data. Step 1. First, check whether there are any files on the disk you need to save: lsblk The screenshot below shows the list. For creating the described partitions, we will use a 25 GB disk — sda. It currently has Debian 11 installed, which does not contain important files. Step 2. To partition the disk, enter the following command: cfdisk /dev/sda Step 3. In the window that opens, you need to delete all existing partitions. To do this, select a partition and use the Delete button in the lower menu. Step 4. Next, select the New button in the lower menu to create a new partition. Step 5. Then specify the size of the partition to be created. In our case, this is 300 MB for UEFI. Step 6. In the next window, choose Primary. Step 7. The partition is now created, and you need to specify its type. Go to the Type menu and select EFI. Step 8. Now move to the Free space and create 2 more partitions, repeating steps 4 through 7. Partition details were listed at the beginning of this chapter. Step 9. Once all partitions have been created, go to the Write button and select it. To confirm, type yes in the field that appears. Step 10. Partitioning is now complete. To exit the tool, select the Quit button in the lower menu. Step 11. You can verify your work using the lsblk command again. Check in the output that all changes have been successfully applied. 3. Formatting and Mounting the Created Partitions At this stage, the created partitions will be formatted and mounted. Remember, all data will be erased in this process! Step 1. For the first partition, format it using the following command: mkfs.fat -F32 /dev/sda1 This command will create a FAT32 filesystem, which is the recommended format for the UEFI partition. Step 2. Next, assign it a mount point: mkdir /mnt/efi mount /dev/sda1 /mnt/efi Step 3. For the second partition, perform special formatting: mkswap /dev/sda2 Step 4. Then activate the swap partition: swapon /dev/sda2 Step 5. Finally, format the system’s root partition: mkfs.ext4 /dev/sda3 Step 6. After formatting, create its mount point: mount /dev/sda3 /mnt After completing the formatting and mounting, your partitions will be ready for installing and configuring Arch Linux and its main components. 4. Installing the Main Arch Linux Components Step 1. First, let’s install the OS and its core components: pacstrap /mnt base linux grub openssh nano dhcpcd Step 2. Once the installation finishes, you need to generate the fstab file: genfstab -U /mnt >> /mnt/etc/fstab Generating the fstab file makes partition mounting management easier and ensures automatic and consistent mounting at system startup. 5. System Configuration Step 1. To configure Arch Linux after installation, you need to chroot into the OS without rebooting: arch-chroot /mnt Step 2. First, install the nano text editor: pacman -S nano Step 3. Uncomment the encoding for English in the relevant file (you would edit locale.gen): nano /etc/locale.gen Uncomment the line for en_US.UTF-8. After this, save the changes and exit nano, then generate the locales: locale-gen To enable the English language, execute: echo "LANG=en_US.UTF-8" > /etc/locale.conf Step 4. At this step, set up the system clock. For example:  ln -sf /usr/share/zoneinfo/Europe/Nicosia /etc/localtime The region is set. Now synchronize the hardware clock: hwclock --systohc Step 5. Next, set the hostname for your system: echo "hostname" > /etc/hostname Step 6. As the second-to-last step, set the root password. Run: passwd You will be prompted to enter and confirm the password. Step 7. Lastly, set up the previously installed GRUB bootloader to boot the server: grub-install --target=i386-pc /dev/sda Then create the GRUB configuration file: grub-mkconfig -o /boot/grub/grub.cfg This command will automatically configure GRUB. Step 8. Arch Linux is now successfully installed. Exit the chroot: exit Then go to the Access tab in your control panel and switch the server to standard boot mode. After that, click Save and Reboot. You can remove the additional disk after this step. Step 9. The system will boot, but it is not ready for use yet. First, connect to the server and enable the DHCP client daemon: systemctl enable dhcpcd Then start it: systemctl start dhcpcd Make sure the service shows the status active (running). Step 10. Next, configure the SSH connection. First, create a backup of the sshd configuration: cp /etc/ssh/sshd_config /etc/ssh/backup.sshdconf Then set PermitRootLogin to Yes in the /etc/ssh/sshd_config file: nano /etc/ssh/sshd_config Finally, enable the SSH daemon: systemctl enable sshd And start it: systemctl start sshd When checking with systemctl status sshd, the service should show active (running) status. Don’t forget to add and configure SSH keys before connecting to the server. 6. Additional Configuration The installation is complete, but you can also perform additional system configuration by reviewing the official Arch Linux setup documentation. To install packages, use the command: pacman -S package_name To update the system, use: pacman -Suy Conclusion In this guide, we reviewed the process of installing Arch Linux on your cloud server and performed its basic configuration. We used a temporary Debian 11 OS and an additional disk for the installation image. By following these steps, you can create a powerful and flexible virtual environment for developing, testing, and running applications based on Arch Linux.
03 July 2025 · 8 min to read

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