Struct BusyboxBlockTools 

pub struct BusyboxBlockTools { /* private fields */ }

BlockTools over busybox applets — the System VM’s userland.

Every operation runs <busybox> <applet> …; the applets are losetup and blockdev. BusyBox’s losetup has no long options at all (util-linux/losetup.c: [-rP] [-o OFS] {-f|LOOPDEV} FILE), so util-linux’s atomic allocate-and-report form -f --show is an unrecognized-option error there, and -f FILE attaches without printing which device it used. Attaching is therefore two applet runs: losetup -f prints the first free device, then losetup [-r] /dev/loopN FILE attaches to exactly that device. Another process can claim the queried device in between (mount -o loop, a concurrent template build), in which case the attach fails and attach_loop re-queries and retries, up to [ATTACH_ATTEMPTS] times.

Implementations

impl BusyboxBlockTools

pub const DEFAULT_PATH: &'static str = "/bin/busybox"

Where the System VM’s EROFS rootfs installs busybox.

pub fn new(busybox: impl Into<PathBuf>) -> BusyboxBlockTools

Use the busybox binary at busybox.

Trait Implementations

impl BlockTools for BusyboxBlockTools

fn attach_loop( &self, backing: &Path, read_only: bool, ) -> Result<String, SnapshotError>

losetup -f, then losetup [-r] /dev/loopN FILE, retried when the queried device is claimed by someone else before the attach lands. A lost race shows up either as the kernel’s EBUSY from LOOP_CONFIGURE/LOOP_SET_FD — busybox prints “Device or resource busy” — or, when busybox notices the device is taken before it issues the ioctl, as a failure with whatever stale errno text it had on hand, so the classifier also asks sysfs whether the device gained a backing file. Any other failure is reported with busybox’s stderr.

fn detach_loop(&self, device: &str) -> Result<(), SnapshotError>

Detach a loop device.

fn device_sectors(&self, device: &str) -> Result<u64, SnapshotError>

Size of a block device in 512-byte sectors.

impl Clone for BusyboxBlockTools

fn clone(&self) -> BusyboxBlockTools

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BusyboxBlockTools

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for BusyboxBlockTools

fn default() -> BusyboxBlockTools

Returns the “default value” for a type.