In an earlier article, I suggested using the following command for duplicating files and directory trees:
$ find . -depth | cpio -pdmv dest_dir
Since the focus of that tutorial was the find utility, I didn't discuss cpio in depth.
cpio can create and extract archives on diskette, tape or in files using eight different archive formats, including tar. It can also create an almost perfect duplicate of a directory tree, preserving file ownership, modes, and access times. Since cpio is designed to accept a list of files such as the output of ls or find, it is more suited for comprehensive backup systems than tools like conventional tar; the set of files processed can be easily controlled programmatically.
cpio also has some less obvious advantages. The default cpio format uses the space on tape much more efficiently than the conventional tar format, and it can also skip damaged sections of archives and continue during restore operations, instead of quitting completely.
GNU tar, which will be covered in an upcoming tutorial, addresses many of these issues. However, when creating archives for other platforms that do not have the GNU utilities available, cpio is an excellent alternative.
Two of the reasons why cpio is not used are readily apparent. The list of possible command line switches fills nearly half a typewritten page, and since it does not accept file names or wildcards as arguments, novices can find it pretty intimidating. But cpio can be worth the extra effort.
cpio has three modes of operation. Pass-through mode, which is what I used in the example above for duplication, create mode, which is used for creating archives, and extract mode, which is used for extracting files from archives.
As its name implies, in pass-through mode cpio acts as a conduit for copying lists of files from one destination to another. The ability to do this while creating subdirectories as needed and handling special files makes it a crucial tool for any system administrator to be familiar with.
For example, one common situation on a multi-user system is the need for more drive space for user directories. The administrator will need to perform the following steps: add an additional drive to the system, create one or more file systems, copy the user directories from the old file system to the new one, and then, depending upon the circumstances, change the file system mount points in order to make the transition unobtrusive.
There are three methods available for copying the users' files over to the new disk. One is to use tar to archive the files and extract them to the new area. This requires the time necessary to archive and extract the files.
Another is to use cp's recursive mode to copy them directly. This mode copies only regular files and links. It also follows symbolic links, which can duplicate a lot of files when used carelessly.
Of course, few system administrators know exactly what is in their users' directories. A developer may have special files such as sockets or pipes. Any user may have files with special permissions in order to prevent unwanted access. Administrators do not have time to inspect home directories that carefully, and many users do not want them to anyway.
$ find . -depth | cpio --pass-through \ --preserve-modification-times \ --make-directories --verbose /mnt/export
This command causes find to output the name of every file under the present directory. (The -depth option insures that directory names are output before the names of the files in them.) cpio reads these file names in and copies them to /mnt/export.
The switches passed to cpio are:
--pass-throughOperate in pass-through mode.
--preserve-modification-timesSet the modification times of the new files to that of the old ones.
--make-directoriesCreate directories when necessary. (This option works when restoring archives, also.)
--verboseVerbose mode. This mode will produce output for all files. An alternative is the -dot option which only produces a . for each file processed. (These options work in all modes.)
The command above creates an exact duplicate of the original directory, regardless of the types of files or any special file modes that were set.
If the files are being copied to the same file system, the --link option can be used to hard link files when necessary.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.View Now!
|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- Managing Linux Using Puppet
- SUSE LLC's SUSE Manager
- My +1 Sword of Productivity
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Non-Linux FOSS: Caffeine!
- Doing for User Space What We Did for Kernel Space
- Google's SwiftShader Released
- Parsing an RSS News Feed with a Bash Script
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide