Deploying SUSE Linux Micro Using Network PXE Boot

Each image has the following subvolumes:

/home
/root
/opt
/srv
/usr/local
/var

The /etc directory is mounted as overlayFS, where the upper directory is mounted to /var/lib/overlay/1/etc/.

You can recognize the subvolumes mounted by default by the option x-initrd.mount in /etc/fstab. Other subvolumes or partitions must be configured either by Ignition or Combustion.

If you want to add a new user or modify any of the files on a subvolume that is not mounted by default, you need to declare such subvolume first so that it is mounted as well.

To configure and use the network connection during the first boot, add the following statement to script:

# combustion: network

Using this statement passes the rd.neednet=1 argument to dracut. The network configuration defaults to using DHCP. If a different network configuration is needed, proceed as described in Section 2.2.2.1.3, “Performing modifications in the initramfs”.

If you do not use the statement, the system remains configured without any network connection.

You may need to perform changes to the initramfs environment, for example, to write a custom network configuration for NetworkManager into /etc/NetworkManager/system-connections/. To do so, use the prepare statement.

For example, to create a connection with a static IP address and configure DNS:

#!/bin/bash
# combustion: network prepare
set -euxo pipefail
          
nm_config() {
  umask 077 # Required for NM config
  mkdir -p /etc/NetworkManager/system-connections/
  cat >/etc/NetworkManager/system-connections/static.nmconnection <<-EOF
  [connection]
  id=static
  type=ethernet
  autoconnect=true
          
  [ipv4]
  method=manual
  dns=192.168.100.1
  address1=192.168.100.42/24,192.168.100.1
EOF
}
          
if [ "${1-}" = "--prepare" ]; then
  nm_config # Configure NM in the initrd
  exit 0
fi
          
# Redirect output to the console
exec > >(exec tee -a /dev/tty0) 2>&1
          
  nm_config # Configure NM in the system
  curl example.com

# Close outputs and wait for tee to finish
exec 1>&- 2>&-; wait;

# Leave a marker
echo "Configured with combustion" > /etc/issue.d/combustion

Some processes may be run in background, for example, the tee process that redirects output to the terminal. To ensure that all running processes are completed before the script execution finishes, add the following line:

exec 1>&- 2>&-; wait;

SUSE Linux Micro raw images are delivered with a default partitioning scheme. You might want to use a different partitioning. The following set of example snippets moves the /home to a different partition.

Note: Performing changes outside of directories included in snapshots

The following script performs changes that are not included in snapshots. If the script fails and the snapshot is discarded, certain changes remain visible and cannot be reverted, for example, the changes to the /dev/vdb device.

The following snippet creates a GPT partitioning schema with a single partition on the /dev/vdb device:

sfdisk /dev/vdb <<EOF
sleep 1
label: gpt
type=linux
EOF

partition=/dev/vdb1

As the sfdisk command may take longer time to complete, postpone label by using the sleep command after sfdisk.

The partition is formatted to Btrfs:

wipefs --all ${partition}
mkfs.btrfs ${partition}

Possible content of /home is moved to the new /home folder location by the following snippet:

mount /home
mount ${partition} /mnt
rsync -aAXP /home/ /mnt/
umount /home /mnt

The snippet below removes an old entry in /etc/fstab and creates a new entry:

awk -i inplace '$2 != "/home"' /etc/fstab
echo "$(blkid -o export ${partition} | grep ^UUID=) /home btrfs defaults 0 0" >>/etc/fstab

As some services, such as Cockpit, require login using a non-root user, define at least one unprivileged user here. Alternatively, you can create such a user from a running system as described in Section 5.2, “Adding users”.

To add a new user account, first create a hash string that represents the user's password. Use the openssl passwd -6 command.

After you obtain the password hash, add the following lines to the script:

mount /home
useradd -m EXAMPLE_USER
echo 'EXAMPLE_USER:PASSWORD_HASH' | chpasswd -e

Before you set the root password, generate a hash of the password, for example, by using the openssl passwd -6. To set the password, add the following line to the script:

echo 'root:PASSWORD_HASH' | chpasswd -e

The following snippet creates a directory to store the root's SSH key and then copies the public SSH key located on the configuration device to the authorized_keys file.

mkdir -pm700 /root/.ssh/
cat id_rsa_new.pub >> /root/.ssh/authorized_keys

Note

The SSH service must be enabled in case you need to use remote login via SSH. For details, refer to Section 2.2.2.1.9, “Enabling services”.

To enable system services, for example, the SSH service, add the following line to script:

systemctl enable sshd.service

Important: Network connection and registering your system may be necessary

As certain packages may require additional subscription, you may need to register your system beforehand. An available network connection may also be needed to install additional packages.

During the first boot configuration, you can install additional packages to your system. For example, you can install the vim editor by adding:

zypper --non-interactive install vim-small

Note

Bear in mind that you will not be able to use zypper after the configuration is complete and you boot to the configured system. To perform changes later, you must use the transactional-update command to create a changed snapshot.

The disks attribute is a list of devices that enables you to define partitions on these devices. The disks attribute must contain at least one device, other attributes are optional. The following example uses a single virtual device and divides the disk into four partitions:

{
  "ignition": {
    "version": "3.0.0"
  },
  "storage": {
    "disks": [
      {
        "device": "/dev/vda",
        "partitions": [
          {
            "label": "root",
            "number": 1,
            "typeGuid": "4F68BCE3-E8CD-4DB1-96E7-FBCAF984B709"
          },
          {
            "label": "boot",
            "number": 2,
            "typeGuid": "BC13C2FF-59E6-4262-A352-B275FD6F7172"
          },
          {
            "label": "swap",
            "number": 3,
            "typeGuid": "0657FD6D-A4AB-43C4-84E5-0933C84B4F4F"
          },
          {
            "label": "home",
            "number": 4,
            "typeGuid": "933AC7E1-2EB4-4F13-B844-0E14E2AEF915"
          }
        ],
        "wipeTable": true
      }
    ]
  }
}

The raid is a list of RAID arrays. The following attributes of raid are mandatory:

For example:

{
  "ignition": {
    "version": "3.0.0"
  },
  "storage": {
    "raid": [
      {
        "devices": [
          "/dev/sda",
          "/dev/sdb"
        ],
        "level": "raid1",
        "name": "system"
      }
    ]
  }
}

Note: Ignition does not perform modifications to mount units

The file system attribute does not modify mount units. If you add a new partition or remove an existing partition, you must manually adjust the mount units.

filesystems must contain the following attributes:

The following example demonstrates using the filesystems attribute. The /opt directory will be mounted to the /dev/sda1 partition, which is formatted to Btrfs. The device will not be erased.

For example:

{
  "ignition": {
    "version": "3.0.0"
  },
  "storage": {
    "filesystems": [
      {
        "device": "/dev/sda1",
        "format": "btrfs",
        "path": "/opt",
        "wipeFilesystem": false
      }
    ]
  }
}

Normally, a regular user's home directory is located in the /home/USER_NAME directory. Since /home is not mounted by default in the initrd, the mount has to be explicitly defined for the user creation to succeed:

{
  "ignition": {
    "version": "3.1.0"
  },
  "passwd": {
    "users": [
      {
        "name": "root",
        "passwordHash": "PASSWORD_HASH",
        "sshAuthorizedKeys": [
          "ssh-rsa SSH_KEY_HASH"
        ]
      }
    ]
  },
  "storage": {
    "filesystems": [
      {
        "device": "/dev/sda3",
        "format": "btrfs",
        "mountOptions": [
          "subvol=/@/home"
        ],
        "path": "/home",
        "wipeFilesystem": false
      }
    ]
  }
}

You can use the files attribute to create any files on your machine. Bear in mind that to create files outside the default partitioning schema, you need to define the directories by using the filesystems attribute.

In the following example, a host name is created by using the files attribute. The file /etc/hostname will be created with the sl-micro1 host name:

Important

Keep in mind that JSON accepts file modes in decimal numbers, for example, 420.

JSON:

{
  "ignition": {
    "version": "3.0.0"
  },
  "storage": {
    "files": [
      {
        "overwrite": true,
        "path": "/etc/hostname",
        "contents": {
          "source": "data:,sl-micro1"
        },
        "mode": 420
      }
    ]
  }
}

The directories attribute is a list of directories that will be created in the file system. The directories attribute must contain at least one path attribute.

For example:

{
  "ignition": {
    "version": "3.0.0"
  },
  "storage": {
    "directories": [
      {
        "path": "/home/tux",
        "user": {
          "name": "tux"
        }
      }
    ]
  }
}