Add support for reading and mounting block devices from the configuration file #10
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Add information to README regarding the new changes in urunit and specifically for the support of a configuration file for the environment variables and the proccess execution environment. Furthermore, rephrase some comments in the code and reduce the search area in the config buffer for searching the configuration for the application execution environment. Signed-off-by: Charalampos Mainas <cmainas@nubificus.co.uk>
Read from the configuration the respective info for mounting attached block devices to the respective mountpoint. In particular the configuration for the block mounts has the following format: UBS ID: <serial_id> MP: <mountpoint> ... UBE Therefore, for every block device there is a pair of ID and MP where ID refers to the serial ID of the device and MP refers to the mountpoint of that block device. Signed-off-by: Charalampos Mainas <cmainas@nubificus.co.uk>
Discover every block device from its serial ID or its order in the config and create all the necessary directories for the mountpoint. Currently, urunit will only look for virtio block devices (vd[a-z]), since urunc will use virtIO for passing a block device to the VM. We might want to revisit this in case urunc uses other types of block devices apart virtio-block. Signed-off-by: Charalampos Mainas <cmainas@nubificus.co.uk>
Make sure that all external filesystem mounts are unmounted before shuttidng down to avoid any corruptions. External means all mounts that use an external to the current VM source (e.g. block devices network filesystems). For the time being urunit checks the filesystem type in the mountinfo and compares it with some well known block, network and cloud-based filesystems. We might want to update this list in the future. Signed-off-by: Charalampos Mainas <cmainas@nubificus.co.uk>
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Add support for reading the list of block devices that should be mounted before the execution of the application. The list is tored in the configuration file with the following format:
Given such a list,
urunitfor each pair of serial id and mountpoint will search all virtio block devices (vd[a-z]) and compare the serial IDs. If they match,urunitwill create all necessary directories for the mountpoint and mount the device in the given mountpoint.It is important to note, that the current approach assumes that all block devices will be virtio-based (since
uruncuses only virtIO for block devices) and there are no more than 26 devices (a-z). However, the current approach is easily extensible for more devices.At last, in case of a failure all created directories will get removed and before shutting down,
urunitwill unmount all mounted filesystems with an external source. External means a source outside of the VM (e.g. block, network).