cpio(C)

Syntax

cpio -i [ -6AbBcdfkmnqrsStTuvV ] [-C bufsize ] [ [ -I file [, file ... ] ]
[ -M message ] ] [ -Pifd,ofd ] [ pattern ... ]

cpio -p [ -adlLmruvV ] [ -Pifd,ofd ] directory

Description

There are three main options to cpio which determine its mode of operation. These modes are used to create an archive (cpio -o), extract files from an archive (cpio -i), and copy files from one filesystem to another (cpio -p). There are a number of secondary options, which are interpreted differently depending on which mode of operation cpio is in.

-o

(copy out) Reads a list of pathnames from the standard input, and copies those files onto the standard output together with pathname and status information. Output is padded to a 512-byte boundary by default.

-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 the wildcard patterns are selected. (See ``Using patterns'' for details of the notation used.) Extracted files are conditionally created and copied into the current directory tree in accordance with the secondary options described below.

If cpio is used to copy files by a process without appropriate privileges, the access permissions are set in the same fashion that creat(S) would have set them when given the mode argument, matching the file permissions supplied by the c_mode field of the cpio format. The owner and group of the files will be that of the current user unless the user is root, which causes cpio to retain the owner and group of the files of the previous cpio -o.

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NOTE: If cpio -i tries to create a file that already exists and the existing file is the same age or newer, cpio will output a warning message and not replace the file. (The -u option can be used to unconditionally overwrite the existing file.)

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-p

(pass) Reads the standard input to obtain a list of pathnames of files that are conditionally created and copied into the destination directory tree based upon the options described below. Archives of text files created by cpio are portable between implementations of UNIX System V.

-6

Process a UNIX System Sixth Edition format file. Used only with the -i option.

-a

Reset access times of input files after they have been copied. Access times are not reset for linked files when cpio -pla is specified.

-A

Suppress absolute filenames. A leading ``/'' character is removed from the filename during copy-in. If a pattern is provided, it should match the relative (rather than the absolute) pathname.

-b

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

-B

Block input/output 5,120 bytes to the record. The default buffer size is 512 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/rdsk/f0q15dt.)

-c

For portability, write header information in ASCII character form. Always use this option when the origin and destination machines are of different types.

-C bufsize

Block input/output bufsize bytes to the record, where bufsize is replaced by a positive integer. The default buffer size is 512 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/c0s0.) When used with the -K option, bufsize is forced to be a 1KB multiple.

-d

Create directories as needed.

-f

Copy in all files except those in patterns. (See the paragraph on cpio -i for a description of patterns.)

-H format

format may take any of the following values:

bin

(binary format) This is a non-portable version of the -c header format.

crc

(new character format with checksum) Write checksum information in the header of each file. This option uses the SVR4 extended ASCII header format.

newc

(new character format without checksum) Write archives using the SVR4 extended ASCII header format.

odc

(old character format) This has the same functionality as -c.

-I file[, file ... ]

Read the contents of file as input. If file is a character-special device, when the first medium is full, replace the medium and type a carriage return to continue to the next medium. You can perform an unattended multi-archive restore if you specify a comma-separated list of files.

Use only with the -i option.

-k

Attempt 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.

-K volumesize

Specify the size of the media volume. Must be in 1KB blocks. For example, a 1.2MB floppy disk has a volumesize of 1200. Must include the -C option with a bufsize multiple of 1KB. If you specify an incorrect size with -K, the command executes without error, but cpio generates the message ``out of sync: bad magic'' when the volume is read. (-K is not available with cpio -i.)

Note that this option is not needed with SCSI tape devices.

-l

Link files rather than copying them whenever possible. Used only with the -p option.

-L

Follow symbolic links.

This option requires that you use the -follow option to find(C) when it is used in conjunction with cpio.

-m

Retain previous file modification time. This option is ineffective on directories that are being copied.

-M message

Define 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 the message to print the sequence number of the next medium needed to continue.

-n

Calculate the checksum value for each file read from an archive (the checksum value is equivalent to that produced by the command sum -r). Filetypes other than regular files produce a checksum of 0 (zero). This option is intended to be used in conjunction with the -itv options; the first entry on each output line is the checksum of an archived file.

-O file[, file ... ]

Direct the output of cpio to file. If file is a character-special device, when the first medium is full, replace the medium and type a carriage return to continue to the next medium. You can change the end-of-media (EOM) message using the -M option.

You can perform an unattended multi-archive backup if you specify a comma-separated list of files. Unless you use SCSI devices, you should specify the volume size using the -K option. Note that cpio assumes that all specified devices have the same volume size.

Use only with the -o option.

-Pifd,ofd

Use file descriptors ifd and ofd for input from and output to a parent process. Any end-of-media (EOM) message is written to ofd rather than to /dev/tty. This option is only useful to programmers who want to write applications that communicate with cpio after a fork(S) and exec(S) by a parent process. The file descriptors must be opened prior to, and remain open on the invocation of cpio by the exec call.

-q

Extract files quickly. cpio extracts only the specified files from the archive and then stops. Shell regular expressions (wildcards) cannot be used in the filenames to be extracted.

-r

Rename files interactively. If the user types a null line, the file is skipped. If the user types a ``.'', the original pathname will be copied.

-s

Swap bytes within each half word. Use only with the -i option.

-S

Swap halfwords within each word. Use only with the -i option.

-T

Truncate long filenames to 14 characters. Use only with the -i option.

-t

Print a table of contents of the input. No files are created.

-u

Copy unconditionally (normally, an older file will not replace a newer file with the same name).

-v

(verbose) Print a list of filenames. When used with the -t option, the table of contents looks like the output of an ls -l command (see ls(C)).

-V

(special verbose) Print a dot for each file seen. This shows cpio is working without printing filenames.

Absolute and relative pathnames

The first command archives the file /u/bulls/eye, including its absolute pathname, as arcfile1. The second command archives eye as arcfile2, without storing any information about the path.

If you restore from arcfile1, eye will be written back to the directory /u/bulls no matter what your working directory. Restoring from arcfile2 will write eye to your current directory. In either case, you are not allowed to restore the file to a directory if you do not have write permission on that directory.

When making a cpio archive, consider whether you will always want to restore the files with absolute pathnames. You can extract files archived with absolute pathnames into their original directory, whatever your current working directory. If necessary, you can specify the -A option to suppress the absolute pathname, and extract files into a different path.

If you opt to archive files using relative pathnames, you will have to change directory to the one where the archive was created in order to extract the files with their original pathnames.

Handling multiple-volume archives

   If you want to go on, type device/filename when ready.

The -I and -O options allow you to read and write archives using multiple devices. This may be useful if you wish to perform an unattended backup or restore and have several archive devices available. If cpio runs out of devices it will prompt you to replace the medium in the last device in the list. It will repeat this action until the end of the archive.

Transferring files between different systems

You should also use one of the options -c, -H crc, -H newc or -H odc when transferring files between different systems. These options write the header information in a portable ASCII character form.

The -H newc and -H crc options are suitable for systems that understand the SVR4 extended-ASCII cpio archive format.

cpio is capable of recognizing the cpio format that was used to create an archive.

You can also use the file(C) command to discover the format type used by a cpio archive.

Using patterns

In patterns, metacharacters ?, , and [ ... ] also match the slash (/) character, and backslash (\) is an escape character. A ``!'' metacharacter means not. (For example, !abc* would exclude all files that begin with abc.)

Multiple patterns may be specified. However, if no pattern is given, the default pattern is ``'' (that is, select all files).

See regexp(M) for more information about shell regular expressions.

Each pattern must be enclosed in double quotes to prevent the shell from expanding it before it is passed to cpio.

Exit values

0

successful completion

>0

an error occurred

Examples

Creating archives

The -v option is used to output a list of filenames as they are extracted.

You can also direct the output to a device instead of a file (here specifying a blocking factor using the -B option):

ls | cpio -ocvB -O /dev/rfd096ds15

These files are stored with pathnames relative to the current directory. In this way, they can be extracted into any desired destination directory.

If you use find with cpio, you can place conditions on which files are to be archived. For example, you can choose to archive:

• Files of a given size (using the -size option of find).

• Files which have had their contents accessed (-atime), or modified (-mtime) in a given time period.

• Files which have had details such as their ownership, type, number of links, or file size changed in a given time period (-ctime).

• Files with certain permissions, such as executable files (-perm).

• Files owned by certain users (-user) or groups (-group).

You should also use the -follow option of find if you follow symbolic links using the -L option of cpio.

You can create a multivolume archive of the entire filesystem on floppies using the -O option of cpio:

find / -depth -print | cpio -ovcBK 1200 -O /dev/rfd096ds15

This archive stores the files with absolute pathnames. When extracted, they will be put in exactly the same places in the directory structure. (If necessary, you can suppress the leading / of absolute pathnames, using the -A option, to change them to relative ones.)

To archive using relative pathnames, change directory to the one to be archived (for example /u), and specify a relative path (.), instead of an absolute one (/u), to find:

cd /u
find . -depth -print | cpio -ocvB -O /dev/rct0

To archive onto block devices (divisions. partitions, or whole disks) larger than 2GB, pipe cpio output through the dd(C) command using the conv=bmode option:

find . -depth -print | cpio -ovcC8192 | dd of=/dev/my_spare_division conv=bmode bs=8k

The -mount option of find limits the archive to the mounted filesystem where the search starts. For example, you might want to archive just those files on the filesystem (/), omitting any in filesystems mounted below / (depending on the way your system was installed, this may include /usr or /u):

find . -depth -mount -print | cpio -ocvB -O /dev/rct0

To limit the archive to just those files modified within the last seven days, use the -mtime option of find:

find . -depth -mount -mtime -7 -print | cpio -ocvB -O /dev/rct0

Extracting files from an archive

cat newfile | cpio -icvd "memo/a1" "info/b"

Files that match the patterns memo/a1 and info/b are extracted from the archive file, newfile. (If no patterns were given, all files from newfile would be extracted.) The -d option creates the directories, memo and info, below the current directory if they are not already present, and places the extracted files in the appropriate directories. If an archive has been created using absolute pathnames, the files to be read have to be specified with their original pathnames. The files would then be extracted into the same directories.

If the archive had been written to a tape drive, you might use:

cpio -icdv -I /dev/rct0 "memo/a1" "memo/b"

The -d option will cause cpio to create directories as needed.

To read an archive from a block device larger than 2GB, use the conv=bmode option of the dd(C) command to read the data and pipe its output to cpio:

dd if=/dev/my_spare_division conv=bmode bs=8k | cpio -ivcC8192

Verifying an archive

If you want to verify the checksums of files in an archive, use the -n option to display these:

cpio -invt -I /dev/rct0

Copying a directory structure

Reading from and writing to several devices

This example restores files from a two-volume archive using two SCSI tape drives:

cpio -iv -I /dev/rStp0,/dev/rStp1

Directories with versioning enabled

Limitations

• Archives written with a character header using the -H crc or -H newc options are not readable on systems that do not recognize the SVR4 extended-ASCII cpio archive format. The -c or -H odc options should be used to write archives that are to be read by these systems.

• The -c, -H bin and -H odc format only allows 16-bit inode numbers. To backup files with 32-bit inode numbers, cpio will generate its own inode/device numbers. There is a possibility that cpio will run out of inode/device numbers when archiving files using this format. If this should happen, the -H newc or -H crc formats should be used; these extended headers store all 32 bits of a file's inode.

• You may run out of inodes if you are trying to restore an archived 32-bit inode number filesystem on a 16-bit inode number filesystem.

• When using the expanded ASCII format (-H newc or -H crc options), the SVR4 version of cpio defers archiving an inode's data until it sees the last hard link to it or EOF. cpio then writes the headers of the links seen previously with their filesizes set to zero. It follows these with the inode data for the last link. When restoring from an archive, the SVR4 cpio may create a read-only directory before attempting to write file data in that directory. This will be unsuccessful unless you are root; using the -depth option to find does not help in these circumstances.

  The SCO version of cpio overcomes this problem by writing the same file data for each hard link. When restoring from an archive, it recreates the hard links so they reference a single inode. If you use the SVR4 cpio to restore from an SCO cpio archive, each link points to a separate copy of the original inode.

• When cpio(C) is used on the root filesystem in conjunction with the -mount option to the find(C) command, mount points are not backed up. This is because -mount skips mounted filesystems. Unless these filesystems are unmounted, the mount points are skipped as well. When restoring the root filesystem, you may need to recreate the mount points manually before restoring the filesystems associated with them. For example, after you restore the root filesystem, you may need to create the /stand directory before restoring your backup of the boot filesystem.

• Pathnames are restricted to 1024 characters.

• cpio interprets the list of filenames read from its standard input literally; if a filename has prefixed or postfixed whitespace, cpio assumes that this is part of the filename.

• Only root 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.

• Irwin tape drives should not be used for multivolume cpio backups because of the variation in the effective size of each tape.

Open UNIX 8 compatibility notes

See also

Standards conformance

AT&T SVID Issue 2;
X/Open CAE Specification, Commands and Utilities, Issue 4, 1992: note that this command is marked as to be withdrawn.