CPIO(1) User Commands CPIO(1)

NAME

cpio - copy file archives in and out

SYNOPSIS

cpio -i [-bBcdfkmPqrsStuvV6@/] [-C bufsize] [-E file]
[-H header] [-I [-M message]] [-R id] [pattern]...


cpio -o [-aABcLPqvV@/] [-C bufsize] [-H header]
[-O file [-M message]]


cpio -p [-adlLmPquvV@/] [-R id] directory

DESCRIPTION

The cpio command copies files into and out of a cpio archive. The cpio
archive can span multiple volumes. The -i, -o, and -p options select the
action to be performed. The following list describes each of the actions.
These actions are mutually exclusive.

Copy In Mode

cpio -i (copy in) extracts files from the standard input, which is
assumed to be the product of a previous cpio -o command. Only files with
names that match one of the patterns are selected. See sh(1) and OPERANDS
for more information about pattern. Extracted files are conditionally
copied into the current directory tree, based on the options described
below. The permissions of the files are those of the previous cpio -o
command. The owner and group are the same as the current user, unless the
current user has the {PRIV_FILE_CHOWN_SELF} privilege. See chown(2). If
this is the case, owner and group are the same as those resulting from
the previous cpio -o command. Notice that if cpio -i tries to create a
file that already exists and the existing file is the same age or younger
(newer), cpio outputs a warning message and not replace the file. The -u
option can be used to unconditionally overwrite the existing file.

Copy Out Mode

cpio -o (copy out) reads a list of file path names from the standard
input and copies those files to the standard output, together with path
name and status information in the form of a cpio archive. Output is
padded to an 8192-byte boundary by default or to the user-specified block
size (with the -B or -C options) or to some device-dependent block size
where necessary (as with the CTC tape).

Pass Mode

cpio -p (pass) reads a list of file path names from the standard input
and conditionally copies those files into the destination directory tree,
based on the options described below.


If the underlying file system of the source file supports detection of
holes as reported by pathconf(2), the file is a sparse file, and the
destination file is seekable, then holes in sparse files are preserved in
pass mode, otherwise holes are filled with zeros.


cpio assumes four-byte words.


If, when writing to a character device (-o) or reading from a character
device (-i), cpio reaches the end of a medium (such as the end of a
diskette), and the -O and -I options are not used, cpio prints the
following message:

To continue, type device/file name when ready.


To continue, you must replace the medium and type the character special
device name (/dev/rdiskette for example) and press RETURN. You might want
to continue by directing cpio to use a different device. For example, if
you have two floppy drives you might want to switch between them so cpio
can proceed while you are changing the floppies. Press RETURN to cause
the cpio process to exit.

OPTIONS

The following options are supported:

-i
(copy in) Reads an archive from the standard input and
conditionally extracts the files contained in it and places them
into the current directory tree.


-o
(copy out) Reads a list of file path names from the standard input
and copies those files to the standard output in the form of a cpio
archive.


-p
(pass) Reads a list of file path names from the standard input and
conditionally copies those files into the destination directory
tree.


The following options can be appended in any sequence to the -i, -o, or
-p options:

-a
Resets access times of input files after they have been
copied, making cpio's access invisible. Access times are
not reset for linked files when cpio -pla is specified.


-A
Appends files to an archive. The -A option requires the -O
option. Valid only with archives that are files, or that
are on floppy diskettes or hard disk partitions. The effect
on files that are linked in the existing portion of the
archive is unpredictable.


-b
Reverses the order of the bytes within each word. Use only
with the -i option.


-B
Blocks input/output 5120 bytes to the record. The default
buffer size is 8192 bytes when this and the -C options are
not used. -B does not apply to the -p (pass) option.


-c
Reads or writes header information in ASCII character form
for portability. There are no UID or GID restrictions
associated with this header format. Use this option between
SVR4-based machines, or the -H odc option between unknown
machines. The -c option implies the use of expanded device
numbers, which are only supported on SVR4-based systems.
When transferring files between SunOS 4 or Interactive UNIX
and the Solaris 2.6 Operating environment or compatible
versions, use -H odc.


-C bufsize
Blocks input/output bufsize bytes to the record, where
bufsize is replaced by a positive integer. The default
buffer size is 8192 bytes when this and -B options are not
used. -C does not apply to the -p (pass) option.


-d
Creates directories as needed.


-E file
Specifies an input file (file) that contains a list of
filenames to be extracted from the archive (one filename
per line).


-f
Copies in all files except those in patterns. See OPERANDS
for a description of pattern.


-H header
Reads or writes header information in header format. Always
use this option or the -c option when the origin and the
destination machines are different types. This option is
mutually exclusive with options -c and -6.

Valid values for header are:

bar
bar head and format. Used only with the -i
option (read only).


crc | CRC
ASCII header with expanded device numbers
and an additional per-file checksum. There
are no UID or GID restrictions associated
with this header format.


odc
ASCII header with small device numbers.
This is the IEEE/P1003 Data Interchange
Standard cpio header and format. It has
the widest range of portability of any of
the header formats. It is the official
format for transferring files between
POSIX-conforming systems (see
standards(7)). Use this format to
communicate with SunOS 4 and Interactive
UNIX. This header format allows UIDs and
GIDs up to 262143 to be stored in the
header.


tar | TAR
tar header and format. This is an older
tar header format that allows UIDs and
GIDs up to 2097151 to be stored in the
header. It is provided for the reading of
legacy archives only, that is, in
conjunction with option -i.

Specifying this archive format with option
-o has the same effect as specifying the
"ustar" format: the output archive is in
ustar format, and must be read using -H
ustar.


ustar | USTAR
IEEE/P1003 Data Interchange Standard tar
header and format. This header format
allows UIDs and GIDs up to 2097151 to be
stored in the header.

Files with UIDs and GIDs greater than the limit stated
above are archived with the UID and GID of 60001. To
transfer a large file (8 Gb - 1 byte), the header format
can be tar|TAR, ustar|USTAR, or odc only.


-I file
Reads the contents of file as an input archive, instead of
the standard input. If file is a character special device,
and the current medium has been completely read, replace
the medium and press RETURN to continue to the next medium.
This option is used only with the -i option.


-k
Attempts to skip corrupted file headers and I/O errors that
might be encountered. If you want to copy files from a
medium that is corrupted or out of sequence, this option
lets you read only those files with good headers. For cpio
archives that contain other cpio archives, if an error is
encountered, cpio can terminate prematurely. cpio finds the
next good header, which can be one for a smaller archive,
and terminate when the smaller archive's trailer is
encountered. Use only with the -i option.


-l
In pass mode, makes hard links between the source and
destination whenever possible. If the -L option is also
specified, the hard link is to the file referred to by the
symbolic link. Otherwise, the hard link is to the symbolic
link itself. Use only with the -p option.


-L
Follows symbolic links. If a symbolic link to a directory
is encountered, archives the directory referred to by the
link, using the name of the link. Otherwise, archives the
file referred to by the link, using the name of the link.


-m
Retains previous file modification time. This option is
ineffective on directories that are being copied.


-M message
Defines a message to use when switching media. When you use
the -O or -I options and specify a character special
device, you can use this option to define the message that
is printed when you reach the end of the medium. One %d can
be placed in message to print the sequence number of the
next medium needed to continue.


-O file
Directs the output of cpio to file, instead of the standard
output. If file is a character special device and the
current medium is full, replace the medium and type a
carriage return to continue to the next medium. Use only
with the -o option.


-P
Preserves ACLs. If the option is used for output, existing
ACLs are written along with other attributes, except for
extended attributes, to the standard output. ACLs are
created as special files with a special file type. If the
option is used for input, existing ACLs are extracted along
with other attributes from standard input. The option
recognizes the special file type. Notice that errors occurs
if a cpio archive with ACLs is extracted by previous
versions of cpio. This option should not be used with the
-c option, as ACL support might not be present on all
systems, and hence is not portable. Use ASCII headers for
portability.


-q
Quiet. Suppresses the number of blocks message that
normally is printed after the copy is completed.


-r
Interactively renames files. If the user types a carriage
return alone, the file is skipped. If the user types a
``.'', the original pathname is retained. Not available
with cpio -p.


-R id
Reassigns ownership and group information for each file to
user ID. (ID must be a valid login ID from the passwd
database.) This option is valid only when id is the
invoking user or the super-user. See NOTES.


-s
Swaps bytes within each half word.


-S
Swaps halfwords within each word.


-t
Prints a table of contents of the input. If any file in the
table of contents has extended attributes, these are also
listed. No files are created. -t and -V are mutually
exclusive.


-u
Copies unconditionally. Normally, an older file is not
replaced a newer file with the same name, although an older
directory updates a newer directory.


-v
Verbose. Prints a list of file and extended attribute
names. When used with the -t option, the table of contents
looks like the output of an ls -l command (see ls(1)).


-V
Special verbose. Prints a dot for each file read or
written. Useful to assure the user that cpio is working
without printing out all file names.


-6
Processes a UNIX System Sixth Edition archive format file.
Use only with the -i option. This option is mutually
exclusive with -c and -H.


-@
Includes extended attributes in archive. By default, cpio
does not place extended attributes in the archive. With
this flag, cpio looks for extended attributes on the files
to be placed in the archive and add them, as regular files,
to the archive. The extended attribute files go in the
archive as special files with special file types. When the
-@ flag is used with -i or -p, it instructs cpio to restore
extended attribute data along with the normal file data.
Extended attribute files can only be extracted from an
archive as part of a normal file extract. Attempts to
explicitly extract attribute records are ignored.


-/
Includes extended system attributes in archive. By default,
cpio does not place extended system attributes in the
archive. With this flag, cpio looks for extended system
attributes on the files to be placed in the archive and add
them, as regular files, to the archive. The extended
attribute files go in the archive as special files with
special file types. When the -/ flag is used with -i or -p,
it instructs cpio to restore extended system attribute data
along with the normal file data. Extended system attribute
files can only be extracted from an archive as part of a
normal file extract. Attempts to explicitly extract
attribute records are ignored.

OPERANDS

The following operands are supported:

directory
A path name of an existing directory to be used as the
target of cpio -p.


pattern
Expressions making use of a pattern-matching notation
similar to that used by the shell (see sh(1)) for filename
pattern matching, and similar to regular expressions. The
following metacharacters are defined:

*
Matches any string, including the empty string.


?
Matches any single character.


[...]
Matches any one of the enclosed characters. A pair
of characters separated by `-' matches any symbol
between the pair (inclusive), as defined by the
system default collating sequence. If the first
character following the opening `[' is a `!', the
results are unspecified.


!
The ! (exclamation point) means not. For example,
the !abc* pattern would exclude all files that
begin with abc.

In pattern, metacharacters ?, *, and [...] match the slash
(/) character, and backslash (\) is an escape character.
Multiple cases of pattern can be specified and if no pattern
is specified, the default for pattern is * (that is, select
all files).

Each pattern must be enclosed in double quotes. Otherwise,
the name of a file in the current directory might be used.

USAGE

See largefile(7) for the description of the behavior of cpio when
encountering files greater than or equal to 2 Gbyte (2^31 bytes).

EXAMPLES

The following examples show three uses of cpio.

Example 1: Using standard input

example% ls | cpio -oc > ../newfile


When standard input is directed through a pipe to cpio -o, as in the
example above, it groups the files so they can be directed (>) to a
single file (../newfile). The -c option insures that the file is portable
to other machines (as would the -H option). Instead of ls(1), you could
use find(1), echo(1), cat(1), and so on, to pipe a list of names to cpio.
You could direct the output to a device instead of a file.

Example 2: Extracting files into directories

example% cat newfile | cpio -icd "memo/a1" "memo/b*"


In this example, cpio -i uses the output file of cpio -o (directed
through a pipe with cat), extracts those files that match the patterns
(memo/a1, memo/b*), creates directories below the current directory as
needed (-d option), and places the files in the appropriate directories.
The -c option is used if the input file was created with a portable
header. If no patterns were given, all files from newfile would be placed
in the directory.

Example 3: Copying or linking files to another directory

example% find . -depth -print | cpio -pdlmv newdir


In this example, cpio -p takes the file names piped to it and copies or
links (-l option) those files to another directory, newdir. The -d option
says to create directories as needed. The -m option says to retain the
modification time. (It is important to use the -depth option of find(1)
to generate path names for cpio. This eliminates problems that cpio
could have trying to create files under read-only directories.) The
destination directory, newdir, must exist.


Notice that when you use cpio in conjunction with find, if you use the -L
option with cpio, you must use the -follow option with find and vice
versa. Otherwise, there are undesirable results.


For multi-reel archives, dismount the old volume, mount the new one, and
continue to the next tape by typing the name of the next device (probably
the same as the first reel). To stop, type a RETURN and cpio ends.

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment variables
that affect the execution of cpio: LC_COLLATE, LC_CTYPE, LC_MESSAGES,
LC_TIME, TZ, and NLSPATH.

TMPDIR
cpio creates its temporary file in /var/tmp by default.
Otherwise, it uses the directory specified by TMPDIR.

EXIT STATUS

The following exit values are returned:

0
Successful completion.


>0
An error occurred.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|CSI | Enabled |
+--------------------+-----------------+
|Interface Stability | Committed |
+--------------------+-----------------+

SEE ALSO

ar(1), cat(1), echo(1), find(1), ls(1), pax(1), setfacl(1), sh(1),
tar(1), chown(2), archives.h(3HEAD), attributes(7), environ(7),
fsattr(7), largefile(7), standards(7)

NOTES

The maximum path name length allowed in a cpio archive is determined by
the header type involved. The following table shows the proper value for
each supported archive header type.


Header type Command line options Maximum path name length
BINARY "-o" 256
POSIX "-oH odc" 256
ASCII "-oc" 1023
CRC "-oH crc" 1023
USTAR "-oH ustar" 255


When the command line options "-o -H tar" are specified, the archive
created is of type USTAR. This means that it is an error to read this
same archive using the command line options "-i -H tar". The archive
should be read using the command line options "-i -H ustar". The options
"-i -H tar" refer to an older tar archive format.


An error message is output for files whose UID or GID are too large to
fit in the selected header format. Use -H crc or -c to create archives
that allow all UID or GID values.


Only the super-user can copy special files.


Blocks are reported in 512-byte quantities.


If a file has 000 permissions, contains more than 0 characters of data,
and the user is not root, the file is not saved or restored.


When cpio is invoked in Copy In or Pass Mode by a user with
{PRIV_FILE_CHOWN_SELF} privilege, and in particular on a system where
{_POSIX_CHOWN_RESTRICTED} is not in effect (effectively granting this
privilege to all users where not overridden), extracted or copied files
can end up with owners and groups determined by those of the original
archived files, which can differ from the invoking user's. This might not
be what the user intended. The -R option can be used to retain file
ownership, if desired, if you specify the user's id.


The inode number stored in the header (/usr/include/archives.h) is an
unsigned short, which is 2 bytes. This limits the range of inode numbers
from 0 to 65535. Files which are hard linked must fall in this inode
range. This could be a problem when moving cpio archives between
different vendors' machines.


You must use the same blocking factor when you retrieve or copy files
from the tape to the hard disk as you did when you copied files from the
hard disk to the tape. Therefore, you must specify the -B or -C option.


During -p and -o processing, cpio buffers the file list presented on
stdin in a temporary file.


The new pax(1) format, with a command that supports it (for example,
tar), should be used for large files. The cpio command is no longer part
of the current POSIX standard and is deprecated in favor of pax.

February 17, 2023 CPIO(1)