Describe the process of creating a RAID 1 (mirroring) array on a Linux system using the `mdadm` utility.

Creating a RAID 1 (mirroring) array on a Linux system using the `mdadm` (Multiple Devices Admin) utility involves several steps. RAID 1 mirroring duplicates data across two or more drives. If one drive fails, the other drive(s) continue to operate, preventing data loss. First, ensure `mdadm` is installed. If not, install it using your distribution's package manager. For example, on Debian-based systems, use `sudo apt-get install mdadm`. On Red Hat-based systems, use `sudo yum install mdadm`. Second, identify the drives you will use for the RAID 1 array. Use commands like `lsblk` or `fdisk -l` to list the available block devices. It is recommended to use drives of the same size and type for optimal performance and capacity utilization. For this example, let's assume you have two drives: `/dev/sdb` and `/dev/sdc`. Third, create the RAID 1 array using the `mdadm` command. The basic syntax is: `sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc`. In this command: `--create` specifies that you are creating a new RAID array. `--verbose` provides detailed output during the creation process. `/dev/md0` is the name of the RAID device (you can choose a different name if you prefer). `--level=1` specifies that you are creating a RAID 1 array. `--raid-devices=2` indicates that the array will consist of two devices. `/dev/sdb` and `/dev/sdc` are the drives that will be part of the RAID array. Fourth, monitor the RAID array creation process. The `mdadm` utility will start creating the RAID 1 array. This process may take some time, depending on the size of the drives. You can monitor the progress using the command: `cat /proc/mdstat`. This will show you the status of the RAID array, including the percentage of data that has been synchronized. Fifth, create a file system on the RAID array. Once the RAID array has been created and synchronized, you can create a file system on it. For example, to create an ext4 file system, use the command: `sudo mkfs.ext4 /dev/md0`. Sixth, create a mount point for the RAID array. A mount point is a directory where the file system will be accessible. For example, you can create a directory named `/data` using the command: `sudo mkdir /data`. Seventh, mount the RAID array to the mount point. Use the command: `sudo mount /dev/md0 /data`. This will make the file system on the RAID array accessible through the `/data` directory. Eighth, configure the system to automatically mount the RAID array on boot. To do this, you need to add an entry to the `/etc/fstab` file. First, determine the UUID of the RAID array using the command: `sudo blkid /dev/md0`. Then, edit the `/etc/fstab` file and add a line similar to: `UUID=your_uuid /data ext4 defaults 0 0`. Replace `your_uuid` with the actual UUID of the RAID array. Ninth, save the RAID configuration. To ensure that the RAID array is properly assembled on boot, save the RAID configuration to the `/etc/mdadm/mdadm.conf` file using the command: `sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf`. Update the initramfs using the command: `sudo update-initramfs -u`. Finally, test the RAID 1 array. Create some files on the RAID array and verify that they are accessible. Then, simulate a drive failure by removing one of the drives from the array. Verify that the RAID array continues to function and that your data is still accessible. You can then add a new drive to the array to rebuild the redundancy.