Install the virtio driver

Only custom images whose operating system kernels support the virtio driver can be imported to Alibaba Cloud Elastic Compute Service (ECS) and then be used to create ECS instances that can start. When you create a custom image based on the data of a source server or import a custom image, make sure that the virtio driver is installed in the image and added to a temporary file system. If the virtio driver is not installed, install the driver.

You can perform the following steps to check whether the operating system kernel of the source server supports the virtio driver and take action based on the check result:

Check whether the operating system kernel of your source server supports the virtio driver.
Perform the following operations based on the check result:
- Add the virtio driver to a temporary file system.
- Install the virtio driver.

Check whether the operating system kernel of your source server supports the virtio driver

Run the following command to check whether the operating system kernel of your source server supports the virtio driver, and determine whether to install the virtio driver for the custom image or whether to add the driver to a temporary file system.

grep -i virtio /boot/config-$(uname -r)

View the command output.

Check the values of the CONFIG_VIRTIO_BLK and CONFIG_VIRTIO_NET parameters in the command output.

If the parameter values are both y, the virtio driver is properly installed. Perform the operations that are described in the What to do next section of this topic.
If the parameters do not exist, the virtio driver is not installed. You must install the driver. For more information, see the Install the virtio driver section of this topic.
If the parameter values are both m, the virtio driver is supported. Run the following command to check whether the driver is added to a temporary file system.
```
lsinitrd /boot/initramfs-$(uname -r).img | grep virtio
```
- If the virtio driver is added to a temporary file system, a command output similar to the one that is shown in the preceding figure is returned. In this case, perform the operations that are described in the What to do next section of this topic.
- Otherwise, add the virtio driver to a temporary file system. For more information, see the Add the virtio driver to a temporary file system section of this topic.

Add the virtio driver to a temporary file system

If the operating system kernel of your source server supports the virtio driver but the virtio driver is not added to a temporary file system, add the driver to a temporary file system. Run one set of the following commands based on the operating system of your source server:

CentOS 6, Anolis OS 7, AlmaLinux 8, or Fedora 33

If the operating system version is CentOS 6, Anolis OS 7, AlmaLinux 8, Fedora 33, or later and the kernel version is later than 2.6.24, run the following commands to repair the temporary file system. You can run the uname -r command to check the kernel version.

Run the following command to open the dracut.conf file:
```
vim /etc/dracut.conf
```
Press the I key to enter the Insert mode and add the following content to the file:
```
add_drivers+="virtio_blk virtio_scsi virtio_net virtio_pci virtio_ring virtio"
```
Press the Esc key, enter :wq, and then press the Enter key to save the change and exit.
Run the following command to regenerate initrd:
```
dracut -f
```
Note
For Red Hat and CentOS 5, we recommend that you upgrade the kernel version to 5.11 before you install the virtio driver.

Debian or Ubuntu

Run the following command to open the modules file:
```
vim /etc/initramfs-tools/modules
```
Press the I key to enter the Insert mode and add the following content to the file:
```
virtio_blk
virtio_scsi
virtio_net
virtio_pci
virtio_ring
virtio
```
Press the Esc key, enter :wq, and then press the Enter key to save the change and exit.
Run the following command to regenerate initrd:
```
update-initramfs -u
```

SUSE or openSUSE

Versions earlier than SUSE 12 SP1 or openSUSE 13
1. Run the following command to open the kernel file:
```
vim /etc/sysconfig/kernel
```
2. Press the I key to enter the Insert mode and add the following content to the file:
```
INITRD_MODULES="virtio_blk virtio_scsi virtio_net virtio_pci virtio_ring virtio"
```
  Press the Esc key, enter :wq, and then press the Enter key to save the change and exit.
3. Run the following command to regenerate initrd:
```
update-initramfs -u
```
SUSE 12 SP1, OpenSUSE 13, or later
1. Run the following command to open the dracut.conf file:
```
vim /etc/dracut.conf
```
2. Press the I key to enter the Insert mode and add the following content to the file:
```
add_drivers+="virtio_blk virtio_scsi virtio_net virtio_pci virtio_ring virtio"
```
  Press the Esc key, enter :wq, and then press the Enter key to save the change and exit.
3. Run the following command to regenerate initrd:
```
dracut -f
```

After the temporary file system is repaired, you can import image files to Alibaba Cloud based on your needs.

Step 1: Download the kernel installation package

Note

In this example, the linux-4.4.24.tar.gz kernel installation package is used. You must modify the commands based on the kernel version of your operating system.

Run the following command to install the components that are required to compile the kernel:
```
yum install -y ncurses-devel gcc make wget
```
Run the following command to query the kernel version of your operating system. In this example, the kernel version is 4.4.24-2.al7.x86_64.
```
uname -r
```
Go to the Index of /pub/linux/kernel/ page to query the download URL of the kernel version repository.
In this example, the download URL of linux-4.4.24.tar.gz is https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.4.24.tar.gz, as shown in the following figure.
Run the following command to switch the directory:
```
cd /usr/src/
```

Run the following command to download the installation package:

wget https://www.kernel.org/pub/linux/kernel/v4.x/linux-4.4.24.tar.gz

Run the following command to decompress the installation package:
```
tar -xzf linux-4.4.24.tar.gz
```
Run the following to create a symbolic link:
```
ln -s linux-4.4.24 linux
```
Run the following command to switch the directory:
```
cd /usr/src/linux
```

Step 2: Compile the kernel

Run the following commands in sequence to compile the kernel:
```
make mrproper
symvers_path=$(find /usr/src/ -name "Module.symvers")
test -f $symvers_path && cp $symvers_path .
cp /boot/config-$(uname -r) ./.config
make menuconfig
```
Note
If an error message is displayed when the make menuconfig command is run, you can troubleshoot the issue based on the message. For example, if the ncurses-devel, bison, and flex components are not installed, you can run the following commands in sequence to install them:
```
yum install  ncurses-devel
yum install  bison
yum install  flex
```
Make virtio-related configurations when the following page is displayed.
Note
If you select the configurations that contain asterisks (*), the virtio driver is compiled into the kernel. If you select configurations that contain m, the virtio driver is compiled into a module and the module is inserted into the kernel when the driver starts.
1. Configure the Virtualization options.
  1. Press the spacebar key to select Virtualization and press the Enter key to view the list of options.
  2. Check that the Kernel-based Virtual Machine (KVM) support option is selected.
2. Configure the Processor type and features options.
  1. Go back to the main menu, press the up and down arrow keys to select Processor type and features, and then press the Enter key to view the list of options.
  2. Press the spacebar key to select Paravirtualized guest support and press the Enter key to view the list of options.
  3. Check that the KVM paravirtualized clock and KVM Guest support options are selected.
3. Configure the Device Drivers options.
  1. Go back to the main menu, press the up and down arrow keys to select Device Drivers, and then press the Enter key to view the list of options.
  2. Press the spacebar key to select Block devices and press the Enter key to view the list of options.
  3. Check that the Virtio block driver option is selected.
  4. Go back to the list of Device Drivers options, press the up and down arrow keys to select Network device support, and then press the Enter key to view the list of options.
  5. Check that the Virtio network driver option is selected.
4. Press the Esc key to exit the kernel configuration window and select Yes at the prompt to save the .config file.
5. Check whether virtio-related configurations are complete.
  For more information, see the Check whether the operating system kernel of your source server supports the virtio driver section of this topic.
6. (Optional) If virtio-related configurations are not complete, run the following commands in sequence to edit the .config file:
```
make oldconfig
make prepare
make scripts
make
make install
```
7. Run the following commands to check whether the virtio driver is installed:
```
find /lib/modules/"$(uname -r)"/ -name "virtio*" | grep -E "virtio*"
grep -E "virtio*" < /lib/modules/"$(uname -r)"/modules.builtin
```
  If the virtio driver is installed, one of the command outputs contains a list of virtio-related files, such as virtio_blk, virtio_pci, and virtio_console, as shown in the following figure.

What to do next

After the virtio driver is installed, you can perform the following operations: