The cpio command is a Linux utility that is used for creating and restoring backup files. It is used to copy files and directories from one location to another, while preserving the file attributes such as ownership, permissions, and timestamps. Cpio can be used to create archives of files and directories, and also to extract files from existing archives.
Overview
The cpio command has two modes of operation: copy-out and copy-in. The copy-out mode is used to create an archive of files and directories, while the copy-in mode is used to extract files from an existing archive.
Creating an archive
To create an archive using cpio, you need to specify the files and directories to be included in the archive. You can do this by using the find command to generate a list of files and directories, and then piping the output to cpio. Here is an example:
find /path/to/files -print0 | cpio -o --null -H tar > archive.tar
In this example, the find command generates a list of files and directories in the /path/to/files directory, and the -print0 option is used to separate the file names with null characters. The output is then piped to cpio, which creates an archive in tar format. The -H option is used to specify the archive format, and the > operator is used to redirect the output to a file called archive.tar.
Extracting files from an archive
To extract files from an archive using cpio, you need to specify the archive file and the destination directory. Here is an example:
cpio -i --no-absolute-filenames < archive.tar -d /path/to/destination
In this example, the cpio command is used to extract files from the archive.tar file. The -i option is used to specify the copy-in mode, and the –no-absolute-filenames option is used to extract files with their original path relative to the current directory. The < operator is used to read the input from the archive file, and the -d option is used to specify the destination directory.
Options
Here are the available options for the cpio command:
| Option | Description |
|---|---|
| -i | Copy-in mode (extract files from an archive) |
| -o | Copy-out mode (create an archive) |
| -H | Specify the archive format (e.g. tar, cpio) |
| -p | Preserve file permissions and ownership |
| -v | Verbose output |
| -d | Create directories as needed |
| –no-absolute-filenames | Extract files with their original path relative to the current directory |
| –null | Use null characters to separate file names |
Troubleshooting tips
Here are some common issues that you may encounter when using the cpio command:
- If you are creating an archive and the output file is empty, make sure that you have specified the files and directories correctly.
- If you are extracting files from an archive and the files are not being extracted to the correct location, check the destination directory specified in the command.
- If you are using the cpio command to extract files from an archive created on a different system, make sure that the archive format is compatible with cpio.
Notes
- The cpio command is often used in conjunction with other commands such as find and tar to create and extract archives.
- Cpio can be used to copy files and directories to a remote system using the ssh command.