Linux and Unix cpio command

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About cpio
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About cpio

cpio copies files to and from archives.

Syntax

Copy-Out Mode Syntax:

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. Copy-Out mode syntax:

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] 

Copy-In Mode Syntax:

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. Copy-In mode syntax:

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] [-t|--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] [--force-local] 
     [--no-absolute-filenames] [--absolute-filenames] [--sparse] 
     [--only-verify-crc] [--to-stdout] [--quiet] [--rsh-command=command] 
     [--help] [--version] [pattern...] [< archive] 

Copy-Pass Mode Syntax:

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 syntax:

cpio {-p|--pass-through} [-0adlmuvLV] [-R [user][:.][group]] [--null] 
     [--reset-access-time] [--make-directories] [--link] [--quiet] 
     [--preserve-modification-time] [--unconditional] [--verbose] [--dot] 
     [--dereference] [--owner=[user][:.][group]] [--no-preserve-owner] 
     [--sparse] [--help] [--version] destination-directory < name-list 

Description

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.

The following archive formats are supported: binary, old ASCII, new ASCII, CRC, HPUX binary, HPUX old ASCII, old tar, and POSIX.1 tar. The tar format is provided for compatibility 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.

Options

-0, --null Read a list of filenames terminated by a null character, instead of a newline, so that files whose names contain newlines can be archived. GNU find is one way to produce a list of null-terminated filenames. This option may be used in copy-out and copy-pass modes.
-a, --reset-access-time Reset the access times of files after reading them, so that it does not look like they have just been read.
-A, --append Append to an existing archive. Only works in copy-out mode. The archive must be a disk file specified with the -O or -F (-file) option.
-b, --swap Swap both halfwords of words and bytes of halfwords in the data. Equivalent to -sS. This option may be used in copy-in mode. Use this option to convert 32-bit integers between big-endian and little-endian machines.
-B Set the I/O block size to 5120 bytes. Initially the block size is 512 bytes.
--block-size=BLOCK-SIZE Set the I/O block size to BLOCK-SIZE * 512 bytes.
-c Identical to '-H newc'; uses the new (SVR4) portable format. If you want the old portable (ASCII) archive format, use '-H odc' instead.
-C IO-SIZE, --io-size=IO-SIZE Set the I/O block size to IO-SIZE bytes.
-d, --make-directories Create leading directories where needed.
-E FILE, --pattern-file=FILE Read additional patterns specifying filenames to extract or list from FILE. The lines of FILE are treated as if they had been non-option arguments to cpio. This option is used in copy-in mode.
-f, --nonmatching Only copy files that do not match any of the given patterns.
-F, --file=archive Archive filename to use instead of standard input or output. To use a tape drive on another machine as the archive, use a filename that starts with 'HOSTNAME:'. The hostname can be preceded by a username and an '@' to access the remote tape drive as that user, if you have permission to do so (typically an entry in that user's '~/.rhosts' file).
--force-local With -F, -I, or -O, take the archive file name to be a local file even if it contains a colon, which would ordinarily indicate a remote host name.
-H FORMAT, --format=FORMAT Use archive format FORMAT. The valid formats are listed below; the same names are also recognized in all-caps. The default in copy-in mode is to automatically detect the archive format, and in copy-out mode is 'bin'.

bin: The obsolete binary format.

odc: The old (POSIX .1) portable format.

newc: The new (SVR4) portable format, which supports file systems having more than 65536 inodes.

crc: The new (SVR4) portable format with a checksum added.

tar: The old tar format.

ustar: The POSIX .1 tar format. Also recognizes GNU tar archives, which are similar but not identical.

hpbin: The obsolete binary format used by HPUX's cpio (which stores device files differently).

hpodc: The portable format used by HPUX's cpio (which stores device files differently).
-i, --extract Run in copy-in mode. (see 'Copy-in mode').
-I archive Archive filename to use instead of standard input. To use a tape drive on another machine as the archive, use a filename that starts with 'HOSTNAME:'. The hostname can be preceded by a username and an '@' to access the remote tape drive as that user, if you have permission to do so (typically an entry in that user's '~/.rhosts' file).
-k Ignored; for compatibility with other versions of cpio.
-l, --link Link files instead of copying them, when possible.
-L, --dereference Copy the file that a symbolic link points to, rather than the symbolic link itself.
-m, --preserve-modification-time Retain previous file modification times when creating files.
-M MESSAGE, --message=MESSAGE Print MESSAGE when the end of a volume of the backup media (such as a tape or a floppy disk) is reached, to prompt the user to insert a new volume. If MESSAGE contains the string '%d', it is replaced by the current volume number (starting at 1).
-n, --numeric-uid-gid Show numeric UID and GID instead of translating them into names when using the '--verbose' option.
--no-absolute-filenames Create all files relative to the current directory in copy-in mode, even if they have an absolute file name in the archive.
--absolute-filenames This is the default: tell cpio not to strip leading file name components that contain '..' and leading slashes from file names in copy-in mode.
--no-preserve-owner Do not change the ownership of the files; leave them owned by the user extracting them. This is the default for non-root users, so that users on System V don't inadvertently give away files. This option can be used in copy-in mode and copy-pass mode.
-o, --create Run in copy-out mode. (see 'Copy-out mode').
-O archive Archive filename to use instead of standard output. To use a tape drive on another machine as the archive, use a filename that starts with 'HOSTNAME:'. The hostname can be preceded by a username and an '@' to access the remote tape drive as that user, if you have permission to do so (typically an entry in that user's '~/.rhosts' file).
--only-verify-crc Verify the CRC of each file in the archive, when reading a CRC format archive. Do not actually extract the files.
-p, --pass-through Run in copy-pass mode. (see 'Copy-pass mode').
--quiet Do not print the number of blocks copied.
-r, --rename Interactively rename files.
-R [user][:.][group], --owner [user][:.][group] Set the ownership of all files created to the specified user and/or group in copy-out and copy-pass modes. Either the user, the group, or both, must be present. If the group is omitted but the ':' or '.' separator is given, use the given user's login group. Only the super-user can change files' ownership.
--rsh-command=COMMAND Notifies cpio that is should use COMMAND to communicate with remote devices.
-s, --swap-bytes Swap the bytes of each halfword (pair of bytes) in the files. This option can be used in copy-in mode.
-S, --swap-halfwords Swap the halfwords of each word (4 bytes) in the files. This option may be used in copy-in mode.
--sparse Write files with large blocks of zeros as sparse files. This option is used in copy-in and copy-pass modes.
-t, --list Print a table of contents of the input.
--to-stdout Extract files to standard output. This option may be used in copy-in mode.
-u, --unconditional Replace all files, without asking whether to replace existing newer files with older files.
-v, --verbose List the files processed, or with '-t', give an 'ls -l' style table of contents listing. In a verbose table of contents of a ustar archive, user and group names in the archive that do not exist on the local system are replaced by the names that correspond locally to the numeric UID and GID stored in the archive.
-V, --dot Print a '.' for each file processed.
--version Print the cpio program version number and exit.

Examples

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. 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 '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 via 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 '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 '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'.

find . -print | cpio -ocv > /dev/fd0

Above, using the find command would list all files and directories and using the cpio command copy those files listed to the floppy drive.

find . -print | cpio -dumpv /home/users/hope

In the above example the find command would list all files and subdirectories of the current directory, and pipe them to the cpio command, which copies those files to the hope user account.

cpio -icuvd < /dev/fd0

The above command would restore the files back from the floppy.

Related commands

ar — Create, modify, and extract files from archives.
cat — Output the contents of a file.
echo — Output text.
gzip — Create, view the contents of, and extract files from GNU zip archives.
ls — List the contents of a directory or directories.
setfacl — Modify the access control list of a file or files.
tar — Create, modify, list the contents of, and extract files from tar archives.