The cpio command copies files in to and out from a cpio archive. The cpio archive may span multiple volumes. The -i, -o, and -p options select the action to be performed. The following list describes each of the actions (which are mutually exclusive).
cpio -i (copy in) extracts files from the standard input, which is assumed to be the product of a previous cpio -o. Only files with names that match patterns are selected. See sh(1) and OPERANDS for more information about pattern. Extracted files are conditionally created and copied into the current directory tree based on the options described below. The permissions of the files will be those of the previous cpio -o. Owner and group will be the same as the current user unless the current user is super-user. If this is true, owner and group will be the same as those resulting from the previous cpio -o. Note that if cpio -i tries to create a file that already exists and the existing file is the same age or younger (newer), cpio will output a warning message and not replace the file. (The -u option can be used to overwrite, unconditionally, the existing file.)
cpio -o (copy out) reads the standard input to obtain a list of path names and copies those files onto the standard output together with path name and status information. 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).
cpio -p (pass) reads the standard input to obtain a list of path names of files that are conditionally created and copied into the destination directory tree based on the options described below.
Note: 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 may want to continue by directing cpio to use a different device. For example, if you have two floppy drives you may want to switch between them so cpio can proceed while you are changing the floppies. (Simply pressing RETURN causes the cpio process to exit.)
The following options are supported:
(copy in) cpio -i extracts files from the standard input.
(copy out) cpio -o reads the standard input to obtain a list of path names and copies those files onto the standard output.
(pass) cpio -p reads the standard input to obtain a list of path names of files.
The following options can be appended in any sequence to the -o, -i, or -p options:
Resets access times of input files after they have been copied. Access times are not reset for linked files when cpio -pla is specified (mutually exclusive with -m).
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.
Reverses the order of the bytes within each word. (Use only with the -i option.)
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 pass option; -B is meaningful only with data directed to or from a character special device, for example, /dev/rmt/0m.
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 enviornment or compatible versions use -H odc.
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 pass option; -C is meaningful only with data directed to or from a character special device, for example, /dev/rmt/0m.)
Creates directories as needed.
Specifies an input file (file) that contains a list of filenames to be extracted from the archive (one filename per line).
Copies in all files except those in patterns. (See OPERANDS for a description of patterns.)
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 (mutually exclusive with -c and -6). Valid values for header are:
bar head and format. Used only with the -i option ( read only)
ASCII header with expanded device numbers and an additional per-file checksum. There are no UID or GID restrictions associated with this header format.
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(5)). 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 header and format. This header format allows UIDs and GIDs up to 2097151 to be stored in the header.
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 will be 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.
Reads the contents of file as an input archive. 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.
Attempts to skip corrupted file headers and I/O errors that may 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 may terminate prematurely. cpio will find the next good header, which may be one for a smaller archive, and terminate when the smaller archive's trailer is encountered.) Used only with the -i option.
Whenever possible, links files rather than copying them. (Usable only with the -p option.)
Follows symbolic links. The default is not to follow symbolic links.
Retains previous file modification time. This option is ineffective on directories that are being copied (mutually exclusive with -a).
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.
Directs the output of cpio to file. 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.
Preserves ACLs. If the option is used for output, existing ACLs are written along with other 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. Note that errors will occur 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 may not be present on all systems, and hence is not portable. Use ASCII headers for portability.
Interactively renames files. If the user types a carriage return alone, the file is skipped. If the user types a ``.'', the original pathname will be retained. (Not available with cpiocpio -p.)
Reassigns ownership and group information for each file to user ID (ID must be a valid login ID from /etc/passwd). This option is valid only for the super-user.
Swaps bytes within each half word.
Swaps halfwords within each word.
Prints a table of contents of the input. No files are created (mutually exclusive with -V).
Copies unconditionally (normally, an older file will not replace a newer file with the same name).
Verbose. Prints a list of file names. When used with the -t option, the table of contents looks like the output of an ls -l command (see ls(1).)
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.
Processes a UNIX System Sixth Edition archive format file. Use only with the -i option (mutually exclusive with -c and -H).
The following operands are supported:
A path name of an existing directory to be used as the target of cpio -p.
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.
means not. (For example, the !abc* pattern would exclude all files that begin with abc.)
In patterns, 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.
See largefile(5) for the description of the behavior of cpio when encountering files greater than or equal to 2 Gbyte ( 231 bytes).
The following examples show three uses of cpio.
When standard input is directed through a pipe to cpio -o, it groups the files so they can be directed (>) to a single file (../newfile). The -c option insures that the file will be 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% ls | cpio -oc > ../newfile
cpio -i uses the output file of cpio -o (directed through a pipe with cat in the example below), 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% cat newfile | cpio -icd "memo/a1" "memo/b*"
cpio -p takes the file names piped to it and copies or links ( -l option) those files to another directory (newdir in the example below). The -d option says to create directories as needed. The -m option says retain the modification time. (It is important to use the -depth option of find(1) to generate path names for cpio. This eliminates problems cpio could have trying to create files under read-only directories.) The destination directory, newdir, must exist.
example% find . -depth -print | cpio -pdlmv newdir
Note that when you use cpio in conjunction with find, if you use the -L option with cpio then you must use the -follow option with find and vice versa. Otherwise there will be undesirable results.
Note that 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 will end.
See environ(5) for descriptions of the following environment variables that affect the execution of cpio: LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_TIME, TZ, and NLSPATH.
See attributes(5) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
Path names are restricted to 256 characters for the binary (the default) and -H odc header formats. Otherwise, path names are restricted to 1024 characters.
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 will not be saved or restored.
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.
When the Volume Management daemon is running, accesses to floppy devices through the conventional device names (for example, /dev/rdiskette) may not succeed. See vold(1M) for further details.
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 option.