973b5141b3
This is only required in RHEL9.0, but best practice is to always pin these things down. Also increases uniformity between distros. Simplify a bit the volid generator by making it require `rand.Rand` rather than `io.Reader`, and hence eliminating the need for error handling.
163 lines
5 KiB
Go
163 lines
5 KiB
Go
// Disk package contains abstract data-types to define disk-related entities.
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//
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// The disk package is a collection of interfaces and structs that can be used
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// to represent an disk image with its layout. Various concrete types, such as
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// PartitionTable, Partition and Filesystem types are defined to model a given
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// disk layout. These implement a collection of interfaces that can be used to
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// navigate and operate on the various possible combinations of entities in a
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// generic way. The entity data model is very generic so that it can represent
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// all possible layouts, which can be arbitrarily complex, since technologies
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// like logical volume management, LUKS2 container and file systems, that can
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// have sub-volumes, allow for complex layouts.
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// Entity and Container are the two main interfaces that are used to model the
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// tree structure of a disk image layout. The other entity interfaces, such as
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// Sizeable and Mountable, then describe various properties and capabilities
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// of a given entity.
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package disk
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import (
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"encoding/hex"
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"io"
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"math/rand"
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"github.com/google/uuid"
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)
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const (
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// Default sector size in bytes
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DefaultSectorSize = 512
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DefaultGrainBytes = uint64(1048576) // 1 MiB
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// UUIDs
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BIOSBootPartitionGUID = "21686148-6449-6E6F-744E-656564454649"
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BIOSBootPartitionUUID = "FAC7F1FB-3E8D-4137-A512-961DE09A5549"
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FilesystemDataGUID = "0FC63DAF-8483-4772-8E79-3D69D8477DE4"
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FilesystemDataUUID = "CB07C243-BC44-4717-853E-28852021225B"
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EFISystemPartitionGUID = "C12A7328-F81F-11D2-BA4B-00A0C93EC93B"
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EFISystemPartitionUUID = "68B2905B-DF3E-4FB3-80FA-49D1E773AA33"
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EFIFilesystemUUID = "7B77-95E7"
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LVMPartitionGUID = "E6D6D379-F507-44C2-A23C-238F2A3DF928"
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PRePartitionGUID = "9E1A2D38-C612-4316-AA26-8B49521E5A8B"
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RootPartitionUUID = "6264D520-3FB9-423F-8AB8-7A0A8E3D3562"
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)
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// Entity is the base interface for all disk-related entities.
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type Entity interface {
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// IsContainer indicates if the implementing type can
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// contain any other entities.
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IsContainer() bool
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// Clone returns a deep copy of the entity.
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Clone() Entity
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}
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// Container is the interface for entities that can contain other entities.
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// Together with the base Entity interface this allows to model a generic
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// entity tree of theoretically arbitrary depth and width.
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type Container interface {
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Entity
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// GetItemCount returns the number of actual child entities.
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GetItemCount() uint
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// GetChild returns the child entity at the given index.
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GetChild(n uint) Entity
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}
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// Sizeable is implemented by entities that carry size information.
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type Sizeable interface {
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// EnsureSize will resize the entity to the given size in case
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// it is currently smaller. Returns if the size was changed.
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EnsureSize(size uint64) bool
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// GetSize returns the size of the entity in bytes.
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GetSize() uint64
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}
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// A Mountable entity is an entity that can be mounted.
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type Mountable interface {
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// GetMountPoint returns the path of the mount point.
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GetMountpoint() string
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// GetFSType returns the file system type, e.g. 'xfs'.
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GetFSType() string
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// GetFSSpec returns the file system spec information.
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GetFSSpec() FSSpec
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// GetFSTabOptions returns options for mounting the entity.
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GetFSTabOptions() FSTabOptions
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}
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// A MountpointCreator is a container that is able to create new volumes.
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//
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// CreateMountpoint creates a new mountpoint with the given size and
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// returns the entity that represents the new mountpoint.
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type MountpointCreator interface {
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CreateMountpoint(mountpoint string, size uint64) (Entity, error)
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}
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// A UniqueEntity is an entity that can be uniquely identified via a UUID.
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//
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// GenUUID generates a UUID for the entity if it does not yet have one.
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type UniqueEntity interface {
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Entity
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GenUUID(rng *rand.Rand)
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}
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// VolumeContainer is a specific container that contains volume entities
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type VolumeContainer interface {
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// MetadataSize returns the size of the container's metadata (in
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// bytes), i.e. the storage space that needs to be reserved for
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// the container itself, in contrast to the data it contains.
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MetadataSize() uint64
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}
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// FSSpec for a filesystem (UUID and Label); the first field of fstab(5)
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type FSSpec struct {
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UUID string
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Label string
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}
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type FSTabOptions struct {
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// The fourth field of fstab(5); fs_mntops
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MntOps string
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// The fifth field of fstab(5); fs_freq
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Freq uint64
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// The sixth field of fstab(5); fs_passno
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PassNo uint64
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}
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// uuid generator helpers
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// GeneratesnewRandomUUIDFromReader generates a new random UUID (version
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// 4 using) via the given random number generator.
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func newRandomUUIDFromReader(r io.Reader) (uuid.UUID, error) {
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var id uuid.UUID
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_, err := io.ReadFull(r, id[:])
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if err != nil {
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return uuid.Nil, err
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}
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id[6] = (id[6] & 0x0f) | 0x40 // Version 4
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id[8] = (id[8] & 0x3f) | 0x80 // Variant is 10
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return id, nil
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}
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// NewVolIDFromRand creates a random 32 bit hex string to use as a
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// volume ID for FAT filesystems
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func NewVolIDFromRand(r *rand.Rand) string {
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volid := make([]byte, 4)
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len, _ := r.Read(volid)
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if len != 4 {
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panic("expected four random bytes")
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}
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return hex.EncodeToString(volid)
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}
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