(cpio.info.gz) Invoking cpio
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.
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
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, the
directories below 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. Copy-out mode. Using the `.' in
the find statement will give you more flexibility when doing restores,
as it will save file names with a relative path vice a hard wired,
absolute path. The `-depth' option forces `find' to print of the
entries in a directory before printing the directory itself. This
limits the effects of restrictive directory permissions by printing the
directory entries in a directory before the directory name itself.
Extracting an archive requires a bit more thought because cpio will
not create directories by default. Another characteristic, is 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
to 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 file unless told to do so
by the -u option. 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
using 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. Copy-pass mode.
% find . -depth -print0 | cpio --null -pvd new-dir
The 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. Another is `-p', which tells cpio to pass the files it
finds to the directory `new-dir'.
(cpio.info.gz) Invoking cpio
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