tar2ext4

Documentation

Index

• func AppendDMVerity(p *params)
• func AppendVhdFooter(p *params)
• func Convert(r io.Reader, w io.ReadWriteSeeker, options ...Option) error
• func ConvertAndComputeRootDigest(r io.Reader) (string, error)
• func ConvertBackslash(p *params)
• func ConvertTarToExt4(r io.Reader, w io.ReadWriteSeeker, options ...Option) error
• func ConvertToVhd(w io.WriteSeeker) error
• func ConvertWhiteout(p *params)
• func Ext4FileSystemSize(r io.ReadSeeker) (int64, int, error)
• func InlineData(p *params)
• func IsDeviceExt4(devicePath string) bool
• func OnlyAppendVhdFooter(p *params)
• func ReadExt4SuperBlock(devicePath string) (*format.SuperBlock, error)
• func ReadExt4SuperBlockReadSeeker(rsc io.ReadSeeker) (*format.SuperBlock, error)
• type Option
  • func MaximumDiskSize(size int64) Option

Functions

func AppendDMVerity

func AppendDMVerity(p *params)

AppendDMVerity instructs the converter to add a dmverity Merkle tree for the ext4 filesystem after the filesystem and before the optional VHD footer

func AppendVhdFooter

func AppendVhdFooter(p *params)

AppendVhdFooter instructs the converter to add a fixed VHD footer to the file.

func Convert

func Convert(r io.Reader, w io.ReadWriteSeeker, options ...Option) error

Convert wraps ConvertTarToExt4 and conditionally computes (and appends) the file image's cryptographic hashes (merkle tree) or/and appends a VHD footer.

func ConvertAndComputeRootDigest

func ConvertAndComputeRootDigest(r io.Reader) (string, error)

ConvertAndComputeRootDigest writes a compact ext4 file system image that contains the files in the input tar stream, computes the resulting file image's cryptographic hashes (merkle tree) and returns merkle tree root digest. Convert is called with minimal options: ConvertWhiteout and MaximumDiskSize set to dmverity.RecommendedVHDSizeGB.

func ConvertBackslash

func ConvertBackslash(p *params)

ConvertBackslash instructs the converter to replace `\` in path names with `/`. This is useful if the tar file was created on Windows, where `\` is the filepath separator.

func ConvertTarToExt4

func ConvertTarToExt4(r io.Reader, w io.ReadWriteSeeker, options ...Option) error

ConvertTarToExt4 writes a compact ext4 file system image that contains the files in the input tar stream.

func ConvertToVhd

func ConvertToVhd(w io.WriteSeeker) error

ConvertToVhd converts given io.WriteSeeker to VHD, by appending the VHD footer with a fixed size.

func ConvertWhiteout

func ConvertWhiteout(p *params)

ConvertWhiteout instructs the converter to convert OCI-style whiteouts (beginning with .wh.) to overlay-style whiteouts.

func Ext4FileSystemSize

func Ext4FileSystemSize(r io.ReadSeeker) (int64, int, error)

Ext4FileSystemSize reads ext4 superblock and returns the size of the underlying ext4 file system and its block size.

func InlineData

func InlineData(p *params)

InlineData instructs the converter to write small files into the inode structures directly. This creates smaller images but currently is not compatible with DAX.

func IsDeviceExt4

func IsDeviceExt4(devicePath string) bool

IsDeviceExt4 is will read the device's superblock and determine if it is and ext4 superblock.

func OnlyAppendVhdFooter

func OnlyAppendVhdFooter(p *params)

OnlyAppendVhdFooter instructs the converter not to convert but still to add a fixed VHD footer to the file.

func ReadExt4SuperBlock

func ReadExt4SuperBlock(devicePath string) (*format.SuperBlock, error)

ReadExt4SuperBlock reads and returns ext4 super block from given device.

func ReadExt4SuperBlockReadSeeker

func ReadExt4SuperBlockReadSeeker(rsc io.ReadSeeker) (*format.SuperBlock, error)

ReadExt4SuperBlockReadSeeker reads and returns ext4 super block given an io.ReadSeeker.

The layout on disk is as follows: | Group 0 padding | - 1024 bytes | ext4 SuperBlock | - 1 block | Group Descriptors | - many blocks | Reserved GDT Blocks | - many blocks | Data Block Bitmap | - 1 block | inode Bitmap | - 1 block | inode Table | - many blocks | Data Blocks | - many blocks

More details can be found here https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout

Our goal is to skip the Group 0 padding, read and return the ext4 SuperBlock

Types

type Option

type Option func(*params)

Option is the type for optional parameters to Convert.

func MaximumDiskSize

func MaximumDiskSize(size int64) Option

MaximumDiskSize instructs the writer to limit the disk size to the specified value. This also reserves enough metadata space for the specified disk size. If not provided, then 16GB is the default.