October 21, 2021
Unix/Linux command line

How To Use cpio Command Line on Unix/Linux

One of the Unix/Linux commands line related to backup tools is cpio, we have discussed the tar command line in other articles. The cpio command is a tools for creating and extracting archives, or copying files from one place to another. Shortly, cpio command usage is to copy files to and from archives. At this article we will discuss how to use cpio command line on Unix/Linux with examples. We will use CentOS 7 as our operation system on this tutorial.

cpio Command Line Modes

There are three mode types of cpio command, namely : copy-out mode, copy-in mode and copy-pass mode.

Copy-out mode

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-in mode

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-pass 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.

cpio Command Options

cpio has many feature and usage, in practice this command has many options. Here’s several options are accompanying the cpio option, namely :

-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.

The complate references for cpio command options could be found an Unix/Linux manual pages.

cpio Command Examples

Our example scenario in using cpio command line is creating new archive file and extraxting its archive file to a new directory. The environment we have, is a directory with several files on /home/ramans/etc/cups directory, as follow :

[ramans@localhost cups]$ pwd
 [ramans@localhost cups]$ ls -ltr
 total 68
 -rw-r--r--. 1 ramans ramans   319 Jun 22  2015 paps.convs
 drwx------. 2 ramans ramans     6 Aug  9 06:07 ssl
 drwxr-xr-x. 2 ramans ramans     6 Aug  9 06:07 ppd
 drwxr-xr-x. 2 ramans ramans     6 Aug  9 06:07 interfaces
 -rw-r--r--. 1 ramans ramans   186 Aug  9 06:07 snmp.conf
 -rw-r-----. 1 ramans ramans  4504 Aug  9 06:07 cupsd.conf.default
 -rw-r-----. 1 ramans ramans  4504 Aug  9 06:07 cupsd.conf
 -rw-------. 1 ramans ramans     0 Aug  9 06:07 printers.conf
 -rw-r--r--. 1 ramans ramans     0 Aug  9 06:07 lpoptions
 -rw-r--r--. 1 ramans ramans     0 Aug  9 06:07 client.conf
 -rw-------. 1 ramans ramans     0 Aug  9 06:07 classes.conf
 -rw-r--r--. 1 ramans ramans 16072 Aug  9 06:09 cups-browsed.conf.rpmnew
 -rw-r--r--. 1 ramans ramans  1029 Dec 10 23:10 cups-browsed.conf
 -rw-r-----. 1 ramans ramans  3091 Dec 12 19:15 cups-files.conf
 -rw-r-----. 1 ramans ramans   111 Dec 18 17:24 subscriptions.conf.O
 -rw-r-----. 1 ramans ramans   412 Dec 18 17:25 subscriptions.conf
cpio command line to cereate archived file

Create archive file

ls | cpio -ov > archived_file.cpio

The -o option creates the archive, and the-v’ option prints the names of the files archived as they are added.

By using cpio command line, we will create archive file called testcpio.cpio where the file’s content will be having files with .conf extension. Usually, the ls or find command line will be use together with the cpio. We will use cpio command file to create archive file by submitting command :

[ramans@localhost cups]$ ls *.conf| cpio -ov > testcpio.cpio
 19 blocks

Extract Files

cpio -idv < archived_files.cpip

The -i option extracts the archive and the -v shows the file names as they are extracted.

By using cpio command, we extracted the archived files from the directory to the current directory.

[ramans@localhost ~]$ cpio -idv  < /home/ramans/etc/cups/testcpio.cpio 
 19 blocks
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