36 lines
1.5 KiB
Markdown
36 lines
1.5 KiB
Markdown
# BUSE - A block device in userspace
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This piece of software was inspired by FUSE, which allows the development of
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Linux file systems that run in userspace. The goal of BUSE is to allow virtual
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block devices to run in userspace as well. Currently BUSE is experimental and
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should not be used for production code.
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Implementing a block device with BUSE is fairly straightforward. Simply fill
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`struct buse_operations` (declared in `buse.h`) with function pointers that
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define the behavior of the block device, and set the size field to be the
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desired size of the device in bytes. Then call `buse_main` and pass it a
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pointer to this struct. `busexmp.c` is a simple example example that shows how
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this is done.
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The implementation of BUSE itself relies on NBD, the Linux network block device,
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which allows a remote machine to serve requests for reads and writes to a
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virtual block device on the local machine. BUSE sets up an NBD server and client
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on the same machine, with the server executing the code defined by the BUSE
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user.
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## Running the Example Code
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BUSE comes with an example driver in `busexmp.c` that implements a 128 MB
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memory disk. To try out the example code, run `make` and then execute the
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following as root:
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modprobe nbd
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./busexmp /dev/nbd0
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You should then have an in-memory disk running, represented by the device file
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`/dev/nbd0`. You can create a file system on the virtual disk, mount it, and
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start reading and writing files on it:
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mkfs.ext4 /dev/nbd0
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mount /dev/nbd0 /mnt
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