GNU cpio
performs three primary functions. Copying files to an
archive, Extracting files from an archive, and passing files to another
directory tree. An archive can be a file on disk, one or more floppy
disks, or one or more tapes.
When creating an archive, cpio
takes the list of files to be
processed from the standard input, and then sends the archive to the
standard output, or to the device defined by the `-F' option.
See section Copy-out mode. Usually, find
or ls
is used to
provide this list to the standard input. In the following example you
can see the possibilities for archiving the contents of a single
directory.
% ls | cpio -ov > directory.cpio
The `-o' option creates the archive, and the `-v' option
prints the names of the files archived as they are added. Notice that
the options can be put together after a single `-' or can be placed
separately on the command line. The `>' redirects the cpio
output to the file `directory.cpio'.
If you wanted to archive an entire directory tree, the find
command can provide the file list to cpio
:
% find . -print -depth | cpio -ov > tree.cpio
This will take all the files in the current directory and its
sub-directories, and place them in the archive `tree.cpio'. Again
the `-o' creates an archive, and the `-v' option shows you the
name of the files as they are archived. See section Copy-out mode. Using
the `.' argument to find
will give you more flexibility when
doing restores, as it will save file names with a relative path instead
of a hard-wired, absolute path. The `-depth' option forces
`find' to print all the entries in a directory before printing the
directory itself. This limits the effects of restrictive directory
permissions by putting the directory entries into the aarchive before the
directory name itself.
Extracting an archive requires a bit more thought because cpio
will not create directories by default. Also, it will not overwrite
existing files unless you tell it to.
% cpio -iv < directory.cpio
This will retrieve the files archived in the file `directory.cpio' and place them in the present directory. The `-i' option extracts the archive and the `-v' shows the file names as they are extracted. If you are dealing with an archived directory tree, you need to use the `-d' option to create directories as necessary, something like:
% cpio -idv < tree.cpio
This will take the contents of the archive `tree.cpio' and extract
it into the current directory. If you try to extract the files on top of
files of the same name that already exist (and have the same or later
modification time), cpio
will not extract the files unless told to
do so by the `-u' option. See section Copy-in mode.
In copy-pass mode, cpio
copies files from one directory tree to
another, combining the copy-out and copy-in steps without actually
creating an archive. It reads the list of files to copy from the
standard input; the directory into which it will copy them is given as a
non-option argument. See section Copy-pass mode.
% find . -depth -print0 | cpio --null -pvd new-dir
This example shows copying the files of the present directory, and
sub-directories to a new directory called `new-dir'. Some new
options are the `-print0' available with GNU find
, combined
with the `--null' option of cpio
. These two options act
together to send file names between find
and cpio
, even if
special characters are embedded in the file names. The `-p' option
tells cpio
to pass the files it finds to the directory
`new-dir'.
Go to the first, previous, next, last section, table of contents.