dcp¶

SYNOPSIS¶

dcp [OPTION] SRC DEST

DESCRIPTION¶

Parallel MPI application to recursively copy files and directories.

dcp is a file copy tool in the spirit of cp(1) that evenly distributes the work of scanning the directory tree, and copying file data across a large cluster without any centralized state. It is designed for copying files that are located on a distributed parallel file system, and it splits large file copies across multiple processes.

OPTIONS¶

--bufsize SIZE¶: Set the I/O buffer to be SIZE bytes. Units like "MB" and "GB" may immediately follow the number without spaces (e.g. 8MB). The default bufsize is 4MB.

--chunksize SIZE¶: Multiple processes copy a large file in parallel by dividing it into chunks. Set chunk to be at minimum SIZE bytes. Units like "MB" and "GB" can immediately follow the number without spaces (e.g. 64MB). The default chunksize is 4MB.

--xattrs WHICH¶: Copy extended attributes ("xattrs") from source files to target files. WHICH determines which xattrs are copied. Options are to copy no xattrs, all xattrs, xattrs not excluded by /etc/xattr.conf, or all xattrs except those which have special meaning to Lustre. Certain xattrs control Lustre features on a file-by-file basis, such as how the file data is distributed across Lustre servers. Values must be in {none, all, libattr, non-lustre}. The default is non-lustre.

--daos-api API¶: Specify the DAOS API to be used. By default, the API is automatically determined based on the container type, where POSIX containers use the DFS API, and all other containers use the DAOS object API. Values must be in {DFS, DAOS}.

--daos-preserve FILENAME¶: Option to turn on metadata preservation in DAOS. This should be used in the case that data is being moved to/from DAOS. For instance, if data is being moved from DAOS to Lustre, then the preserve option can be used to write the DAOS container metadata to an HDF5 file. That way, when data is moved back from Lustre to DAOS the container properties can be preserved. A filename to write the metadata to must be specified.

-i, --input FILE¶: Read source list from FILE. FILE must be generated by another tool from the mpiFileUtils suite.

-L, --dereference¶: Dereference symbolic links and copy the target file or directory that each symbolic link refers to.

-P, --no-dereference¶: Do not follow symbolic links in source paths. Effectviely allows symbolic links to be copied when the link target is not valid or there is not permission to read the link's target.

-p, --preserve¶: Preserve permissions, group, and timestamps.

-s, --direct¶: Use O_DIRECT to avoid caching file data.

-S, --sparse¶: Create sparse files when possible.

--progress N¶: Print progress message to stdout approximately every N seconds. The number of seconds must be a non-negative integer. A value of 0 disables progress messages.

-v, --verbose¶: Run in verbose mode.

-q, --quiet¶: Run tool silently. No output is printed.

-h, --help¶: Print a brief message listing the dcp(1) options and usage.

RESTRICTIONS¶

If a long-running copy is interrupted, one should delete the partial copy and run dcp again from the beginning. One may use drm to quickly remove a partial copy of a large directory tree.

To ensure the copy is successful, one should run dcmp after dcp completes to verify the copy, especially if dcp was not run with the -s option.

EXAMPLES¶

To copy dir1 as dir2:

mpirun -np 128 dcp /source/dir1 /dest/dir2

To copy contents of dir1 into dir2:

mkdir /dest/dir2 mpirun -np 128 dcp /source/dir1/\* /dest/dir2

To copy while preserving permissions, group, timestamps, and attributes:

mpirun -np 128 dcp -p /source/dir1/ /dest/dir2

KNOWN BUGS¶

Using the -S option for sparse files does not work yet at LLNL. If you try to use it then dcp will default to a normal copy.

The maximum supported file name length for any file transferred is approximately 4068 characters. This may be less than the number of characters that your operating system supports.