dd - Copy, and optionally convert, a file system resource
dd [-h|--help]
[-V|--version] [operands]
Copy, and optionally convert, a file system resource
Print help
Print version
operands]### Operands
- bs=BYTES : read and write up to BYTES bytes at a time (default: 512); overwrites ibs and obs. - cbs=BYTES : the conversion block size in bytes. Applies to the conv=block, and conv=unblock operations. - conv=CONVS : a comma-separated list of conversion options or (for legacy reasons) file flags. - count=N : stop reading input after N ibs-sized read operations rather than proceeding until EOF. See iflag=count_bytes if stopping after N bytes is preferred - ibs=N : the size of buffer used for reads (default: 512) - if=FILE : the file used for input. When not specified, stdin is used instead - iflag=FLAGS : a comma-separated list of input flags which specify how the input source is treated. FLAGS may be any of the input-flags or general-flags specified below. - skip=N (or iseek=N) : skip N ibs-sized records into input before beginning copy/convert operations. See iflag=seek_bytes if seeking N bytes is preferred. - obs=N : the size of buffer used for writes (default: 512) - of=FILE : the file used for output. When not specified, stdout is used instead - oflag=FLAGS : comma separated list of output flags which specify how the output source is treated. FLAGS may be any of the output flags or general flags specified below - seek=N (or oseek=N) : seeks N obs-sized records into output before beginning copy/convert operations. See oflag=seek_bytes if seeking N bytes is preferred - status=LEVEL : controls whether volume and performance stats are written to stderr.
When unspecified, dd will print stats upon completion. An example is below.
```plain 6+0 records in 16+0 records out 8192 bytes (8.2 kB, 8.0 KiB) copied, 0.00057009 s, 14.4 MB/s
The first two lines are the volume stats and the final line is the performance stats. The volume stats indicate the number of complete and partial ibs-sized reads, or obs-sized writes that took place during the copy. The format of the volume stats is <complete>+<partial>. If records have been truncated (see conv=block), the volume stats will contain the number of truncated records.
Possible LEVEL values are: - progress : Print periodic performance stats as the copy proceeds. - noxfer : Print final volume stats, but not performance stats. - none : Do not print any stats.
Printing performance stats is also triggered by the INFO signal (where supported), or the USR1 signal. Setting the POSIXLY_CORRECT environment variable to any value (including an empty value) will cause the USR1 signal to be ignored.
### Conversion Options
- ascii : convert from EBCDIC to ASCII. This is the inverse of the ebcdic option. Implies conv=unblock. - ebcdic : convert from ASCII to EBCDIC. This is the inverse of the ascii option. Implies conv=block. - ibm : convert from ASCII to EBCDIC, applying the conventions for [, ] and ~ specified in POSIX. Implies conv=block.
- ucase : convert from lower-case to upper-case. - lcase : converts from upper-case to lower-case.
- block : for each newline less than the size indicated by cbs=BYTES, remove the newline and pad with spaces up to cbs. Lines longer than cbs are truncated. - unblock : for each block of input of the size indicated by cbs=BYTES, remove right-trailing spaces and replace with a newline character.
- sparse : attempts to seek the output when an obs-sized block consists of only zeros. - swab : swaps each adjacent pair of bytes. If an odd number of bytes is present, the final byte is omitted. - sync : pad each ibs-sided block with zeros. If block or unblock is specified, pad with spaces instead. - excl : the output file must be created. Fail if the output file is already present. - nocreat : the output file will not be created. Fail if the output file in not already present. - notrunc : the output file will not be truncated. If this option is not present, output will be truncated when opened. - noerror : all read errors will be ignored. If this option is not present, dd will only ignore Error::Interrupted. - fdatasync : data will be written before finishing. - fsync : data and metadata will be written before finishing.
### Input flags
- count_bytes : a value to count=N will be interpreted as bytes. - skip_bytes : a value to skip=N will be interpreted as bytes. - fullblock : wait for ibs bytes from each read. zero-length reads are still considered EOF.
### Output flags
- append : open file in append mode. Consider setting conv=notrunc as well. - seek_bytes : a value to seek=N will be interpreted as bytes.
### General Flags
- direct : use direct I/O for data. - directory : fail unless the given input (if used as an iflag) or output (if used as an oflag) is a directory. - dsync : use synchronized I/O for data. - sync : use synchronized I/O for data and metadata. - nonblock : use non-blocking I/O. - noatime : do not update access time. - nocache : request that OS drop cache. - noctty : do not assign a controlling tty. - nofollow : do not follow system links.
v(uutils coreutils) 0.10.0
Make a bootable USB drive from an isohybrid file (such as `archlinux-xxx.iso`) and show the progress:
dd if=path/to/file.iso of=/dev/usb_drive status=progress
Clone a drive to another drive with 4 MiB block size and flush writes before the command terminates:
dd bs=4194304 conv=fsync if=/dev/source_drive of=/dev/dest_drive
Generate a file with a specific number of random bytes by using kernel random driver:
dd bs=100 count=1 if=/dev/urandom of=path/to/random_file
Benchmark the sequential write performance of a disk:
dd bs=1024 count=1000000 if=/dev/zero of=path/to/file_1GB
Create a system backup, save it into an IMG file (can be restored later by swapping `if` and `of`), and show the progress:
dd if=/dev/drive_device of=path/to/file.img status=progress
The examples are provided by the tldr-pages project <https://tldr.sh> under the CC BY 4.0 License. Please note that, as uutils is a work in progress, some examples might fail.