dd

7.2.7 dd

Convert and copy a file residing in Exascale or a local file system.

Syntax

dd [ --if=name ] [ --of=name ] [ --bs=bytes ] [ --count=num ] 
   [ --ibs=bytes ] [ --obs=bytes ] [ --seek=num ] [ --skip=num ] 
   [ --imirror=num ] [ --omirror=num ] [ --mirror=num ] 
   [ --truncate ] [ --aio=naio ] [ --block ] 
   [ --status=status-level] [ --sparse ]
   [{ -w | --wallet } wallet-location ] 
   [{ -T | --trace } trace-level ] 
   [{ -j | --json } [ --compact ]]

Command Options

The options for the dd command are:

--if: Specifies the name of the input file to use instead of standard input.
--of: Specifies the name of the output file to use instead of standard output.
--bs: Specifies the number of bytes to read and write in each block. The default value is 512.
--count: Specifies the number of input blocks.
--ibs: Specifies the number of bytes to read in each block. The default value is 512.
--obs: Specifies the number of bytes to write in each block. The default value is 512.
--seek: Specifies the number of blocks to skip at the start of the output.
--skip: Specifies the number of blocks to skip at the start of the input.
--imirror: Specifies the input mirror number. The first mirror is 0, the second mirror is 1, and so on. The default value is 255, which means 'read any mirror.'
--omirror: Specifies the output mirror number. The first mirror is 0, the second mirror is 1, and so on. The default value is 255, which means 'write all mirrors.'
--mirror: Specifies the input and output mirror number. The first mirror is 0, the second mirror is 1, and so on. The default value is 255, which means 'all mirrors.'
--truncate Resizes the output file.
--aio: Specifies the number of asynchronous I/O channels used to process the command. Asynchronous I/O enables the command to initiate I/O operations and continue executing other tasks without waiting (blocking) for the I/Os to complete. The default value is 4, which generally provides an optimal balance of performance and resource utilization.
--block: Specifies that the I/O offsets should be divisible by the relevant I/O block size.
--status: Specifies the level of status information output during a long-running operation.

Permitted values are:
- progress: Periodically shows progress statistics.
- none: Suppresses progress statistics and only shows applicable error messages. This is the default setting.
--sparse: Performs the operation in a sparse-aware manner by skipping read and write I/Os for empty source file blocks (blocks containing all zeros) and generating sparse output files.

This option only applies when copying files in Exascale storage.
-w, --wallet: Optionally specifies the path to the Exascale wallet directory.
-T, --trace: Optionally enables tracing, with the trace level (trace-level) set to 1 (minimum tracing), 2 (medium tracing), or 3 (maximum tracing). If the trace level is not specified, then minimum tracing is enabled by default.

The trace file is written to the first accessible location in the following list:
1. If the $ADR_BASE environment variable is set:
```
$ADR_BASE/diag/EXC/xsh_<user-name>/<host-name>/trace/xsh_<date>.trc
```
2. ```
/var/log/oracle/diag/EXC/xsh_<user-name>/<host-name>/trace/xsh_<date>.trc
```
3. ```
/tmp/diag/EXC/xsh_<user-name>/<host-name>/trace/xsh_<date>.trc
```
-j, --json: Displays the output in JSON format.
--compact: Displays JSON formatted output in a compact format, without white space and line breaks.

Examples

Example 7-16 Copy a Specific Portion of an Exascale File

This example demonstrates how to copy a specific section of an Exascale file to a local file. This type of command is valuable for extracting or examining a portion of a large file without copying the entire file.

Using a 16 KB (16,384 bytes) block size, the command skips the first 160 KB (10 blocks) of the Exascale file at @my-data/dbs/t_cf1.f, and then copies the next 32 KB (2 blocks) to the local file at /tmp/16K.file.

$ xsh dd --if=@my-data/dbs/t_cf1.f --of=/tmp/16K.file --bs=16384 --skip=10 --count=2

Parent topic: XSH Command Reference