Boot with GRUB
Using the GRUB command line is cool, but after a few thousand system starts, you will probably get a little tired of entering the same commands at the GRUB prompt and long for something a little more automated. Good news from the GRUB gang: you get a fully configurable menu interface at no extra charge! The GRUB boot menu gives you point-and-shoot boot selection, unattended default boot after a configurable timeout, any number of fallback boots if previous boots fail, toggle between command-line and menu modes, and interactive editing of menu selections and password protection. These features give GRUB an ease of use to match its tremendous functionality.
When GRUB boots, it automatically looks for the /boot/grub/menu.lst file on its boot device (the last three letters are “ELL ess tee” and not “one ess tee”). If the file is found, GRUB automatically enters its menu mode and presents the user with a stunning interface, as shown in Figure 2.
Listing 1 [found at LJ's web site] shows the configuration file responsible for this demonstration menu. As you can see, it is a simple text file typical of many UNIX configuration files, where lines starting with hashes (#) and blank lines are ignored.
The first set of commands sets general configuration variables. The timeout command sets the time in seconds to wait for the user to make a selection before proceeding automatically to the default boot. The default command sets which of the following boot stanzas GRUB should attempt to boot automatically. Boot stanzas are numbered implicitly, starting from zero, according to their order of appearance in the configuration file. This order is also how they will be listed in the menu.
The fallback command specifies which of the boot stanzas to load if the default should fail. It is possible to set more than one fallback, as is shown in the example.
The color command lets you breathe a bit of life into the text-mode menu screen. The syntax for the color command is
color foreground/background [ hilite-fg/hilite-bg ]
where each of the foreground/background colors is specified with a name from the set of black, blue, green, cyan, red, magenta, brown and light-gray; dark-gray, light-blue, light-green, light-cyan, light-cyan, light-red, light-magenta, yellow and white. Among these colors, only the first eight are used for the background. The optional highlight color pair, if specified, will be used to show the current menu selection. When not specified, GRUB will use the inverse of the normal colors.
The rest of the configuration file consists of the boot stanzas for our demonstration system. The title command marks the beginning of a new boot stanza, and its argument is the label that will be displayed for its entry in the menu, from the first non-white-space character to the end of the line. The remaining commands in each stanza are identical to those used when working from the GRUB command line. The exception here is that we no longer need to give a boot command; GRUB does this job without asking.
This example configuration gives only a sample of the many flexible uses of the GRUB boot loader. Besides multiple OSes, you can use GRUB to set up menu selections for test kernels, rescue kernels, different kernel options and so on.
All in all, the GRUB configuration file will be very similar to your /etc/lilo.conf. And after working with the GRUB command line and these examples, it should be a simple matter of firing up your favorite text editor and creating a menu configuration file suitable for your own system and preferences. Don't worry if it's not perfect the first time; you will see that you can make changes interactively, and the GRUB command line is always available as a fallback.
Once you've got your configuration file, mount your GRUB floppy again, and copy the file (say it has been saved as mygrub.conf) into the magic location:
cp mygrub.conf /floppy/boot/grub/menu.lst
Now when you boot with your GRUB floppy—presto!—you will be greeted with a lovely boot menu like the one in Figure 2. If you like, just stare at it for the few seconds it needs to count down from the timeout setting, and then it will automatically boot into your default OS. Or, use the arrow keys to highlight the OS you want to load and press return. Or, type c to go to the now-familiar GRUB command prompt. From the command prompt, press ESC to go back to the boot menu again.
It is also possible to edit the entries displayed in the menu. Typing e will open a simple vi-like editor interface for the highlighted entry. This allows you to adjust or add any settings to the configuration before booting. Any changes made here will then remain in effect for the duration of the GRUB session. To make permanent changes, you will later need to edit the configuration file on the boot disk, saving the changes with your text editor.
Play with your GRUB floppy configuration until you have it set up the way you like. After just a few system boots, you'll be slinging through GRUB like hashbrowns in a diner.
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.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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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