dcp

Copy data between devices, supporting any combination of block devices, XFS files, and raw memory.

Usage

dcp <input@offset:size> <output@offset:size>

Argument Format

Both input and output use the <name>@<offset>:<size> format, and every field is optional:

Field	Description	Default
name	Block device name or XFS file path; omit for raw memory	none (raw memory)
offset	Start offset, decimal or hexadecimal (0x prefix)	0
size	Number of bytes to copy, decimal or hexadecimal	to the end of the device

Device Type Resolution

The name field is resolved in the following order:

1. First matched as a block device name (e.g. blk.0, including partition devices such as blk.0.xstar)
2. If not found, resolved as an XFS file path (requires a mounted filesystem)
3. When name is omitted, the argument refers to raw memory, and offset is the memory address

Notes

• The actual copied size is the smaller of the input available size and the output size
• The input block device is synced before copying; the output block device or file is automatically flushed afterwards
• When the output is a file, offset is ignored and writing always starts at the beginning of the file
• Transfers in 64KB chunks, reporting the total amount and speed when finished

Caveats

• Raw memory access performs no bounds checking; the caller must ensure the address and size are valid
• Writing to a block device is a raw write: NAND devices (e.g. spinand) perform read-modify-write per erase block, so do not overwrite system partitions by mistake

Examples

# Dump memory to a file
dcp @0x80000000:0x1000 /tmp/dump.bin@0:0x1000

# Back up a block device partition to a file
dcp blk.0.xstar@0:0x10000 /tmp/backup.bin@0:0x10000

# Flash an image file to a block device
dcp /tmp/image.bin@0:0x100000 blk.0@0x10000:0x100000

# Read block device content back into memory, inspect with the md command
dcp blk.0@0x10000:0x100 @0x40300000:0x100

# Copy between partitions
dcp blk.0.private@0:0x10000 blk.1@0:0x10000

# Omit size to copy from an offset to the end of the device
dcp blk.0@0x1000 /tmp/full.bin