Checkpoint/Restore In Userspace (CRIU) is a tool that allows freezing a running process on a Linux system and later restoring it. This functionality serves various purposes, including process migration between hosts without the need for shutdown and restart, which is particularly advantageous in high-availability environments. In this article, we'll explore how to configure and use CRIU on the CentOS 7 operating system.
Installing CRIU Before initiating any configuration, CRIU needs to be installed. On CentOS 7, installing CRIU can be done through the EPEL repositories, which requires adding this repository group to your system.
- Adding the EPEL repository:
sudo yum install epel-release - Installing CRIU:
sudo yum install criu
After installation, verify the CRIU version and its availability using the command:
criu --version
Configuring CRIU Configuring CRIU on CentOS 7 doesn’t require extensive changes in the system configuration. However, it's important to ensure that your system and kernel support necessary features such as namespaces and cgroups, which CRIU requires for its operation.
- Check if your kernel supports CRIU:
criu check
If the command returns that your system is compatible, you can proceed. Otherwise, you'll need to make necessary kernel adjustments or updates.
Using CRIU With CRIU, you can perform two main actions: creating a checkpoint of a running application and resuming it from this checkpoint.
- Creating a checkpoint of an application: First, run the application you want to freeze. Then, use CRIU to create its checkpoint:
sudo criu dump -t <PID of the application> --images-dir /path/to/checkpoint/directory --leave-running
This command will create a checkpoint of the running application identified by its PID (Process ID) and save the checkpoint data to the specified directory, while the application will still be running.
- Restoring an application from a checkpoint: To restore an application from a previously created checkpoint, use:
sudo criu restore --images-dir /path/to/checkpoint/directory
This command will restore the application to the state it was in at the time of checkpoint creation.
CRIU is a powerful tool for managing applications on Linux systems, allowing their freezing and resuming without the need for a restart. This guide provided you with basic information on how to install, configure, and use CRIU on CentOS 7. It's important to note that for effective utilization of CRIU, solid knowledge of the Linux operating system and its kernel is required.
