A dedicated unikernel for microservices

Friday, April 20, 2018

Easing the sharing of files between host and guest by using the Qemu Fat feature

Hello folks! I have just committed the first version of a fat driver. This driver together with the vfat interface of Qemu eases the sharing of files between the guest and the host. This new feature relies on the mechanism of Qemu to present to a guest a fat partition from a directory in the host. This mechanism is enabled by passing "-drive file=fat:rw:ToroFiles", where ToroFiles is the path of a directory in the host machine. By doing so, Qemu presents to the guest a new block device in which there is a fat partition that includes all the file structure of the ToroFiles directory. Depending on some flags, the partition can be either fat32 or fat16. From the qemu's source code, it seems fat32 is not tested enough so I decided to support fat16 only. The main benefits of this mechanism is to ease the sharing of files between the guest and the host. The main drawback is you should not modify the directory while the guest is running because Qemu may get confused. To know more about this fetaure in qemu, you can visit https://en.wikibooks.org/wiki/QEMU/Devices/Storage. The commit that adds this feature can be found here https://github.com/MatiasVara/torokernel/commit/2de6631d10202f20db7cef61469ed9e795ed6954. For the moment, the driver allows only read operations. I expect to have writing operations soon.