README.md

bcachectl

A tool for administering bcache devices.

Build requirements

The minimum you need to build is golang installed (eg. 1.17+). Note the lazy script below will download and install golang for you. Optionally, manually install golang and make if you want to build manually or using make.

Install requirements

You will need to install bcache-tools, and a kernel that supports bcache and the bcache kernel module loaded.

Building

Using make (requires go already installed):

make
make install

Manual

go mod init bcachectl
go mod tidy
go build bcachectl.go

This will produce the binary bcachectl in the same dir. You can place in /usr/local/bin or other exec path of your choice.

The lazy way

This will do everything including installing golang for you in /tmp, download files, build and install to /usr/local/bin/bcachectl

curl https://raw.githubusercontent.com/rafalop/bcachectl/main/scripts/install_bcachectl.sh | sudo bash

Usage examples

Format and register a bcache backing device

bcachectl format -B /dev/vdb

Format and register a bcache cache device

bcachectl format -C /dev/vdc

Format and register a bcache device together with a cache device (auto attaches the cache)

bcachectl add -B /dev/vdb -C /dev/vdc

List all bcache devices examples

bcachectl list
bcachectl list -e sequential_cutoff,dirty_data
bcachectl list -f json
bcachectl list -f short

Show detailed information about a bcache device

bcachectl show /dev/vdb
bcachectl show bcache0

Attach an already formatted cache dev to an already formatted backing dev

bcachectl attach /dev/ssd /dev/vda

Detach a cache device (/dev/ssd) from a backing device (/dev/vda)

bcachectl detach /dev/sdd /dev/vda

Change bcache tunable of a bcache device

bcachectl tune bcache0 cache_mode:writeback
bcachectl tune /dev/vdb sequential_cutoff:$((1024*1024))
bcachectl tune /dev/vdb sequential_cutoff:1M

bcache notes/quirks

• if a device is registered and mounted, and your unregister, it will still show the cache dev as registered until you unmount the filesystem