Remember when creating CDs, the root of the CD is relative to the created directory; in this case, cdimage. Once you have your files in this directory, you are ready to create the iso9660 image using the mkisofs command. To create the basic image, use the following command:
mkisofs -r -o cdimage.iso cdimage
The -r option ensures the image contains additional file description data by way of the Rock Ridge protocol, preserving the original file name and setting permissions optimally for CD-ROMs such that read/execute permissions become global, write permissions are cleared, and special mode bits are also cleared since they do not apply on CD-ROMs. The -o option designates the output file (cdimage.iso). The last value is the directory in which the files are located.
Many commercially manufactured Linux CDs, such as Red Hat, are bootable. This isn't difficult to do using the “El Torito” standard. Most newer BIOSes today support the bootable CD feature, and most bootable CDs for the PC are based on El Torito. El Torito makes your CD appear as a floppy, and thus your BIOS can boot it.
If you want a bootable CD, you'll need a 1.44MB boot image intended for a boot floppy. In our distribution example, we could use the boot image used for installation. For distribution_b, the name of the boot image is boot.img. The process by which we make a CD bootable takes place in the creation of the iso9660 image (International Organization for Standardization specification for compact disk read-only memory). Thus, before we create our image, we need to create a directory inside of cdimage to hold the boot image; a directory called boot would work fine. So, we place the image boot.img into cdimage/boot and create the iso9660 image by executing the following command:
mkisofs -r -b boot/boot.img -c boot/boot.cat -o\ cdimage.iso cdimage
Here we have two new options, both of which are used to make the CD bootable. The -b option is followed by the name of the boot image to be booted. Note that the file is relative to the root of the CD. The -c option is followed by the name of the boot catalog required by El Torito; this file is automatically created by mkisofs. Only the more recent versions of mkisofs allow for the automatic creation of the boot catalog; older versions require you to create it yourself.
Before actually burning the CD, take a look at your image layout by mounting it. This is done using a loopback device, so this must be supported in the kernel. The following command will mount your image:
mount -r -t iso9660 -o loop cdimage.iso /mnt
Once you've created your image, bootable or not, you are ready for the final process of burning it onto the CD using either cdrecord or cdwrite. Take the following into consideration before you start:
Make sure the computer isn't experiencing any excessive vibrations.
Make sure the image is on a local hard drive.
Make sure the load on your system isn't too high.
Keeping these three things in mind will help prevent errors during the write process. The CD writer can be put through a test process that won't actually write, but will simulate the entire process. This is done by adding the -dummy option for cdrecord and the -y option for cdwrite. Now all that is left is inserting a blank CD and executing the command that matches your choice of writer.
cdrecord -eject -v -isosize speed=2 dev=0,0\ cdimage.iso cdwrite -ev --device /dev/??? -s 2 cdimage.isoThe first two options for both utilities are eject and verbose. Thus, the CD will eject after the burning process is finished, and the program will run in verbose mode. The option -isosize for cdrecord limits the size of the CD to the size of the iso9660 image. The options speed=2 and -s 2 indicate the speed at which to write to the CD; in this case, the 2 means at 2x. Finally, the options --device, dev=0,0 and /dev/??? set the target device, where /dev/??? should be your CD-R (i.e., /dev/scd0) and 0,0 stands for the SCSI ID and bus in that order.
If all worked out well, congratulations. You now have a full-fledged, iso9660 CD. You can make a CD with other formats just as well. The utility mkhybrid, included with mkisofs, can make images of Joliet and HFS format. It is also possible to make a CD with the EXT2 file system format. Have fun burning!
Alex Withers has been using Linux since 1.1.59. He is currently studying computer science at Gonzaga University and can be reached at email@example.com.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
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.
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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