Managing bcachefs Filesystems (with examples)

Introduction

Bcachefs is a next-generation, general-purpose filesystem that offers features like scalability, caching, and high performance. This article will guide you through various use cases of the bcachefs command, demonstrating how to format, mount, create RAID 0 filesystems, and display disk usage using bcachefs.

Use Case 1: Formatting a partition with bcachefs

sudo bcachefs format path/to/partition

Motivation: This use case is useful when you want to create a new bcachefs filesystem on a specific partition.

Explanation: The format subcommand is used to format a partition with bcachefs. By providing the path/to/partition, you specify the target partition where the new filesystem will be created.

Example Output:

Formatting bcachefs filesystem on /dev/sdb1...
bcachefs successfully formatted on /dev/sdb1.

Use Case 2: Mounting a bcachefs filesystem

sudo bcachefs mount path/to/partition path/to/mountpoint

Motivation: This use case is applicable when you want to mount an existing bcachefs filesystem on a specific partition to a mountpoint.

Explanation: The mount subcommand is used to mount a bcachefs filesystem. By providing the path/to/partition, you specify the partition containing the bcachefs filesystem, and by providing the path/to/mountpoint, you specify the directory where the filesystem will be mounted.

Example Output:

Mounting bcachefs filesystem from /dev/sdb1 to /mnt/bcachefs...
bcachefs filesystem successfully mounted to /mnt/bcachefs.

Use Case 3: Creating a RAID 0 filesystem

sudo bcachefs format --label=ssd.ssd1 path/to/ssd/partition --label=hdd.hdd1 path/to/hdd/partition --replicas=1 --foreground_target=ssd --promote_target=ssd --background_target=hdd

Motivation: This use case is appropriate when you want to create a RAID 0 filesystem with an SSD acting as a cache and an HDD serving as long-term storage.

Explanation: The format subcommand with specific arguments helps create a RAID 0 filesystem. Here, --label=ssd.ssd1 and --label=hdd.hdd1 specify the labels for the SSD and HDD partitions, respectively. --replicas=1 sets the desired number of clone-replicas, which is 1 in this case. --foreground_target specifies the device to be used for foreground writes (SSD), --promote_target specifies the device to promote lower-level clones into foreground (SSD), and --background_target sets the device to be used for background writes (HDD).

Example Output:

Creating a RAID 0 bcachefs filesystem with SSD cache and HDD storage...
bcachefs RAID 0 filesystem successfully created.

Use Case 4: Mounting a multidevice filesystem

sudo bcachefs mount path/to/partition1:path/to/partition2 path/to/mountpoint

Motivation: This use case is ideal when you want to mount a bcachefs multidevice filesystem containing multiple partitions.

Explanation: The mount subcommand is used to mount a multidevice bcachefs filesystem. By providing multiple path/to/partition separated by colons (:), you specify the partitions contributing to the filesystem. The path/to/mountpoint` is the directory where the filesystem will be mounted.

Example Output:

Mounting bcachefs multidevice filesystem from /dev/sdb1:/dev/sdc1 to /mnt/bcachefs...
bcachefs multidevice filesystem successfully mounted to /mnt/bcachefs.

Use Case 5: Display disk usage

bcachefs fs usage --human-readable path/to/mountpoint

Motivation: This use case is useful when you want to check the disk usage of a mounted bcachefs filesystem.

Explanation: The fs usage subcommand is used to retrieve disk usage information. By providing the path/to/mountpoint, you specify the mounted bcachefs filesystem. The --human-readable option formats the output in a human-readable format.

Example Output:

Current disk usage of bcachefs filesystem at /mnt/bcachefs:
Total size: 100 GB
Used: 60 GB
Available: 40 GB

Use Case 6: Display help

bcachefs

Motivation: This use case is applicable when you want to access the help documentation for the bcachefs command.

Explanation: Simply running the bcachefs command without any subcommands or arguments will display the general help information, including a list of available subcommands and their descriptions.

Example Output:

bcachefs - Manage bcachefs filesystems/devices.

Commands:
- format: Format a partition with bcachefs.
- mount: Mount a bcachefs filesystem.
...

Conclusion

The bcachefs command provides various subcommands to manage bcachefs filesystems seamlessly. By understanding and utilizing the different use cases covered in this article, you can easily format, mount, create RAID 0 filesystems, display disk usage, and access help documentation related to bcachefs.