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GNU cpio is a tool for creating and extracting archives, or copying files from one place to another. It handles a number of cpio formats as well as reading and writing tar files. This is the first edition of the GNU cpio documentation and is consistant with GNU cpio 2.5.
1. Introduction 2. Tutorial Getting started. 3. Invoking cpio How to invoke `cpio'. 4. Magnetic Media Using tapes and other archive media. Concept Index Concept index.
-- The Detailed Node Listing ---
Invoking cpio
3.1 Copy-out mode 3.2 Copy-in mode 3.3 Copy-pass mode 3.4 Options
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GNU cpio copies files into or out of a cpio or tar archive, The archive can be another file on the disk, a magnetic tape, or a pipe.
GNU cpio supports the following archive formats: binary, old ASCII, new ASCII, crc, HPUX binary, HPUX old ASCII, old tar, and POSIX.1 tar. The tar format is provided for compatability with the tar program. By default, cpio creates binary format archives, for compatibility with older cpio programs. When extracting from archives, cpio automatically recognizes which kind of archive it is reading and can read archives created on machines with a different byte-order.
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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 3.1 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, 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. See section 3.1 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. See section 3.2 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. See section 3.3 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'.
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3.1 Copy-out mode 3.2 Copy-in mode 3.3 Copy-pass mode 3.4 Options
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In copy-out mode, cpio copies files into an archive. It reads a list of filenames, one per line, on the standard input, and writes the archive onto the standard output. A typical way to generate the list of filenames is with the find command; you should give find the -depth option to minimize problems with permissions on directories that are unreadable. See section 3.4 Options.
cpio {-o|--create} [-0acvABLV] [-C bytes] [-H format] [-M message] [-O [[user@]host:]archive] [-F [[user@]host:]archive] [--file=[[user@]host:]archive] [--format=format] [--message=message][--null] [--reset-access-time] [--verbose] [--dot] [--append] [--block-size=blocks] [--dereference] [--io-size=bytes] [--rsh-command=command] [--help] [--version] < name-list [> archive] |
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In copy-in mode, cpio copies files out of an archive or lists the archive contents. It reads the archive from the standard input. Any non-option command line arguments are shell globbing patterns; only files in the archive whose names match one or more of those patterns are copied from the archive. Unlike in the shell, an initial `.' in a filename does match a wildcard at the start of a pattern, and a `/' in a filename can match wildcards. If no patterns are given, all files are extracted. See section 3.4 Options.
cpio {-i|--extract} [-bcdfmnrtsuvBSV] [-C bytes] [-E file] [-H format] [-M message] [-R [user][:.][group]] [-I [[user@]host:]archive] [-F [[user@]host:]archive] [--file=[[user@]host:]archive] [--make-directories] [--nonmatching] [--preserve-modification-time] [--numeric-uid-gid] [--rename] [--list] [--swap-bytes] [--swap] [--dot] [--unconditional] [--verbose] [--block-size=blocks] [--swap-halfwords] [--io-size=bytes] [--pattern-file=file] [--format=format] [--owner=[user][:.][group]] [--no-preserve-owner] [--message=message] [--help] [--version] [-no-absolute-filenames] [--sparse] [-only-verify-crc] [-quiet] [--rsh-command=command] [pattern...] [< archive] |
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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. See section 3.4 Options.
cpio {-p|--pass-through} [-0adlmuvLV] [-R [user][:.][group]] [--null] [--reset-access-time] [--make-directories] [--link] [--preserve-modification-time] [--unconditional] [--verbose] [--dot] [--dereference] [--owner=[user][:.][group]] [--sparse] [--no-preserve-owner] [--help] [--version] destination-directory < name-list |
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-0, --null
-a, --reset-access-time
-A, --append
-b, --swap
-B
--block-size=BLOCK-SIZE
-c
-C IO-SIZE, --io-size=IO-SIZE
-d, --make-directories
-E FILE, --pattern-file=FILE
-f, --nonmatching
-F, --file=archive
--force-local
-H FORMAT, --format=FORMAT
-i, --extract
-I archive
-k
-l, --link
-L, --dereference
-m, --preserve-modification-time
-M MESSAGE, --message=MESSAGE
-n, --numeric-uid-gid
--no-absolute-filenames
--no-preserve-owner
-o, --create
-O archive
--only-verify-crc
-p, --pass-through
--quiet
-r, --rename
-R [user][:.][group], --owner [user][:.][group]
--rsh-command=COMMAND
-s, --swap-bytes
-S, --swap-halfwords
--sparse
-t, --list
-u, --unconditional
-v, --verbose
-V --dot
--version
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Archives are usually written on removable media--tape cartridges, mag tapes, or floppy disks.
The amount of data a tape or disk holds depends not only on its size, but also on how it is formatted. A 2400 foot long reel of mag tape holds 40 megabytes of data when formated at 1600 bits per inch. The physically smaller EXABYTE tape cartridge holds 2.3 gigabytes.
Magnetic media are re-usable--once the archive on a tape is no longer needed, the archive can be erased and the tape or disk used over. Media quality does deteriorate with use, however. Most tapes or disks should be disgarded when they begin to produce data errors.
Magnetic media are written and erased using magnetic fields, and should be protected from such fields to avoid damage to stored data. Sticking a floppy disk to a filing cabinet using a magnet is probably not a good idea.
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1. Introduction
2. Tutorial
3. Invoking cpio
4. Magnetic Media
Concept Index
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