Debian Package Management, Part 1: A User's Guide
I have not yet found another distribution that makes upgrading to a new version as easy as Debian does. As mentioned previously, when you want to upgrade your version, simply change the distribution part of the URI in /etc/apt/sources.list, then do an apt-get dist-upgrade. Often, it helps to run apt-get dist-upgrade a few times to get everything happily installed and configured. You can only use this to go to a newer version, from stable to frozen, stable to unstable or frozen to unstable. You cannot downgrade.
apt-cache is great for finding information about packages, even packages you don't have installed! The command apt-cache show <package> will print various information about the package, including dependencies, full name, what it provides, the short and long descriptions, and, most importantly, the size when unpacked. apt-cache depends <package> provides a list of what other packages the selected <package> needs installed to work properly. To print a complete list of every package available, use apt-cache pkgnames.
The most useful feature of apt-cache that I've found has to be apt-cache search <string>. This option will search through all package names and descriptions looking for occurrences of your <string> selection. Obviously, this can be a great time-saving device.
To further assist your managing capabilities, there are some options that apt-cache can utilize. For example, -i lists only the important dependencies, -f prints full records (just like “show”) after a search and -names-only limits searches to package names.
While I can usually get by with dpkg for package management, apt-cache for searching and apt-get for installation, sometimes I want to get a better idea of what's available to me. This is where dselect, console-apt and gnome-apt come in.
dselect is the granddaddy of the Debian frontends. As the first part of the installation process, it is the first thing new Debian users are greeted with, and it scares them. And it's true that dselect can be incredibly scary as well as incredibly dense. This section will be the short and sweet introduction to dselect. First, my best advice when using dselect is to read all of the on-screen help. Although not very user-friendly, everything you need to know is contained there.
When you first start dselect, you'll want to go to “[A]ccess” to select the correct access method for installation. Meaning, select “nfs” if you have a local nfs mirror of Debian, and “apt” if you want to install over the Internet (http/ftp) or if you've configured your sources.list for local addresses. Other methods available are CD, Multi-CD (if your distribution has multiple CD-ROMs as opposed to one), Floppy and Mounted.
Once you've selected your access method, dselect needs to find out what packages it has access to; to accomplish this, select “[U]pdate” and wait a minute.
“[S]elect” is where the actual package management happens. First, you'll be presented with a help screen. READ IT! When you finish READING IT, press space to get out of help or “.” to read the keybindings. You can move around the package listings by searching or by using up/down, page-up/page-down, home/end and left/right. The following are some basic, useful keystrokes in dselect:
/ search\ repeats the last search? brings up helpd scrolls down the package informationu scrolls up it
When you've highlighted a package you want to do something with, use:
+ install or upgrade- remove= leave in present state
When you're ready to leave the selection screen, select:
<enter> to confirm, quit and check dependenciesQ to quit, confirm and override dependenciesX or Esc to abandon all changes
After you press return, you may be presented with a list of packages; these may be either dependencies of or conflicts with the packages you selected. Look at the packages; the bottom half of the screen will tell you what the problem is. Once you've resolved these problems, press enter.
After you've made your changes in “[S]elect”, either “[I]nstall” or “[R]emove” which will bring your system up to date with the changes. “[C]onfig” is only necessary if any package configuration failed.
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