TOPIC: OPERATING SYSTEMS
Relocating the Apache web server document root directory in Fedora 12
9th April 2010
So as not to deface anything that is available online on the web, I have a tendency to set up an offline Apache server on a home PC to do any tinkering away from the eyes of the unsuspecting public. Though Ubuntu is my mainstay for home computing, I do have a PC with Fedora installed, and I have been trying to get an Apache instance to start automatically on there unsuccessfully for a few months. While I can start it by running the following command as root, I'd rather not have more manual steps than is necessary.
httpd -k start
The command used by the system when it starts is different and, even when manually run as root, it failed with messages saying that it couldn't find the directory while the web server files are stored. Here it is:
service httpd start
The default document root location on any Linux distribution that I have seen is /var/www and all is very well with this, but it isn't a safe place to leave things if ever a re-installation is needed. Having needed to wipe /var after having it on a separate disk or partition for the sake of one installation, it doesn't look so persistent to me. In contrast, you can safeguard /home by having it on another disk or in a dedicated partition, which means that it can be retained even when you change the distro that you're using. Thus, I have got into the habit of having the root of the web server document root folder in my home area, and that is where I have been seeing the problem.
Because of the access message, I tried using chmod and chgrp, but to no avail. The remedy has to do with reassigning the security contexts used by SELinux. In Fedora, Apache will not work with the context user_home_t that is usually associated with home directories, but needs httpd_sys_content_t instead. To find out what contexts are associated with particular folders, issue the following command:
ls -Z
The final solution was to create a user account whose home directory hosts the root of the web server file system, called www in my case. Then, I executed the following command as root to get things going:
chcon -R -h -t httpd_sys_content_t /home/www
It appears that even the root of the home directory has to have an appropriate security context (/home has home_root_t so that might do the needful too). Without that, nothing will work, even if all is well at the next level down. The switches for chcon command translate as follows:
-R : recursive; applies changes to all files and folders within a directory.
-h : changes apply only to symbolic links and not to where they refer in the file system.
-t : alters context type.
It took a while for all of this stuff about SELinux security contexts to percolate through to the point where I was able to solve the problem. A spot of further inspiration was needed too and even guided my search for the information that I needed. It's well worth trying Linux Home Networking if you need further details. Though there are references to an earlier release of Fedora, the content still applies to later versions of Fedora to the current release, if my experience is typical.
Getting Fedora working in VirtualBox
12th May 2009
After a hiatus induced by disk errors seen on start up, I have gone having a go with Fedora again. In the world of real PC's, its place has been taken by Debian, so virtualisation was brought into play for my most recent explorations. I could have gone with 10, the current stable version, but curiosity got the better of me and I downloaded a pre-release version of 11 instead.
On my way to getting that instated, I encountered two issues. The first of these was boot failure with the message like this:
FATAL: INT18: BOOT FAILURE
As it turned out, that was easily sorted. I was performing the installation from a DVD image mounted as if it were a real DVD, and laziness or some other similar reason had me rebooting with it still mounted. Though there is an option to load the hard disk variant, it wasn't happening, resulting in the message that's above. A complete shutdown and replacement of the virtual DVD with a real one set matters to rights.
The next trick was to get Guest Additions added, but Fedora's 2.6.29 was not what VirtualBox was expecting, and it demanded the same ransom as Debian: gcc, make and kernel header files. Unfamiliarity had me firing up Fedora's software installation software, only to find that Synaptic seems to beat it hands down in the search department. Turning to Google dredged up the following command to be executed, which got me further:
yum install binutils gcc make patch libgomp glibc-headers glibc-devel kernel-headers kernel-devel
However, the installed kernel headers didn't match the kernel, but a reboot fixed that once the kernel was updated. Then, the Guest Additions installed themselves as intended, with necessary compilations to match the installed kernel.
The procedures that I have described here would, it seems, work for Fedora 10; well, they certainly have bequeathed me a working system. I have had a little poke and a beta of Firefox 3.5 is included, and I saw sign of OpenOffice 3.1 too. So, it looks very cutting edge, easily so in comparison with Ubuntu and Debian. Apart from one or niggles, it seems to run smoothly too. Firstly, don't use the command shutdown -h now to close the thing down, or you'll cause VirtualBox to choke. Using the usual means ensures that all goes well, though. The other irritation is that it doesn't connect to the network without a poke from me. Whether SELinux is to blame for this or not, I cannot tell, but it might be something for consideration by the powers than be. That these are the sorts of things that I have noticed should be telling you that I have no major cause for complaint. While I have mulled over a move to Fedora in the past and that option remains as strong as ever, Ubuntu is not forcing me to look at an alternative and the fact that I know how to achieve what I need is resulting in inertia anyway.
On keyboards
17th April 2009
While there cannot be too many Linux users who go out and partner a Microsoft keyboard with their system, my recent cable-induced mishap has resulted in exactly that outcome. Keyboards are such standard items that it is not so possible to generate any excitement about them, apart from RSI-related concerns. While I wasn't about to go for something cheap and nasty that would do me an injury, going for something too elaborate wasn't part of the plan either, even if examples of that ilk from Microsoft and Logitech were sorely tempting.
Shopping in a bricks and mortar store, like I was, has its pluses and its minuses. The main plus points are that you see and feel what you are buying, with the main drawback being that the selection on offer isn't likely to be as extensive as you'd find on the web, even if I was in a superstore. Despite the latter, there was still a good deal available. Though there were PS/2 keyboards for anyone needing them, USB ones seemed to be the main offer, with wireless examples showcased too. Strangely, the latter were only available as kits with mice included, further adding to the cost of an already none too cheap item. The result was that I wasn't lured away from the wired option.
While I didn't emerge with what would have been my first choice because that was out of stock, that's not to say that what I have doesn't do the job for me. The key action is soft and cushioned, which is a change from that to which I am accustomed; some keyboards feel like they belong on a laptop, but not this one. There are other bells and whistles too, with a surprising number of them working. The calculator and email buttons number among these along with the play/pause, back and forward ones for a media player; I am not so convinced about the volume controls though an on-screen indicator does pop up. You'd expect a Microsoft item to be more Windows specific than others, yet mine works as well as anything else in the Ubuntu world and I have no reason to suspect that other Linux distros would spurn it either. Keyboards tend to be one of those "buy-it-and-forget-it" items, and the new arrival should be no different.
Some things that I'd miss on moving from Linux to Windows
17th January 2009
The latest buzz surrounding Windows 7 has caused one observer to suggest that it's about to blast Linux from the desktop. While my experiences might be positive, there are still things that I like about Linux that make me reluctant to consider switching back. Here are a few in no particular order:
Virtual Desktops (or Workspaces)
I find these very handy for keeping things organised when I have a few applications open at the same time. While I think that someone has come with a way of adding the same functionality to Windows, I'd need to go looking for that. Having everything cluttering up a single taskbar would feel a bit limiting.
Symbolic Links
If you have not come across these before, they are a little difficult to explain, but it's great to have the ability to make the contents of a folder appear in more than one place at a time without filling up your hard drive. While it's true to say that Windows 7 gets Libraries, I have a soft spot for the way that Linux does it so simply.
Lack of (intrusive) fidgeting
One of Windows' biggest problems is that it's such a massive target for attacks by the less desirable elements of the web community. The result is a multitude of security software vendors wanting to get their wares onto your PC; it's when they get there that all the fidgeting starts. The cause is the constant need for system monitoring that eats up resources that could be used for other things. Though I know some packages are less intrusive than others, I do like the idea of feeling as if I am in full control of my PC rather someone else taking decisions for me (unavoidable in the world of work, I know). An example of this is Norton's not allowing me to shut it down when it goes rogue, even when acting as Administrator. While I can see the reason for this in that it's trying to hamper the attentions of nefarious malware, it ends up making me feel less than empowered and I also like to feel trusted too. Another thing that I like is the idea of something awaiting my input rather than going away and trying to guess what I need and getting it wrong, an experience that seems typical of Microsoft software.
Command Line
Though this is less of a miss than it used to be, there is now a learning curve with PowerShell's inclusion with Windows 7, and it's not something that I want to foist on myself without my having the time to learn its ins and outs. Though it's not a bad skill to have listed on the proverbial CV, I now know my way around bash and its ilk while knowing where to look when I intend to take things further.
After these, there are other personal reasons for my sticking with Linux, like memories of bad experiences with Windows XP and the way that Linux just seems to get on with the job. Its being free of charge is another bonus, and the freedom to have things as you want makes you feel that you have a safer haven in this ever-changing digital world. While I am not sure if I'd acquire the final version of Windows 7, I am certain that it will not be replacing Linux as my main home computing platform, something that should come as no surprise given what I have said above.
Copying only updated and new files
20th October 2008
With Linux/UNIX, the command line remains ever useful and allows you to do all manner of things, including file copying that only adds new files to a destination. Here's a command that accomplishes this on Linux:
cp -urv [source] [destination]
The u switch does the update while r ensures recursion (by default, cp only copies files from a source directory and not anything sitting in subfolders) and v tells the command to tell the user what is happening.
Though buried and hardly promoted, Windows also has its command line and here's what accomplishes a similar result:
xcopy /d /u [source] [destination]
Anything's better than having to approve or reject every instance where source and destination files are the same or, even worse, to overwrite a file when it is not wanted.
How much space is that folder taking up on your disk?
23rd July 2008
On Windows, it's a matter of right-clicking on the folder and looking in its properties. I am sure that there is a better way of doing it in that ever pervasive operating system but, in the worlds of Linux and UNIX, the command line comes to the rescue as it is wont to do. What follows is the command that I use:
du -sh foldername
The s option makes it present the total space taken up; leaving it out gets you a breakdown of how much space the subfolders are taking up as well. The h makes the sizes output more friendly to human eyes with things like 10K, 79M and 51G littering what you get. The command itself is a much shorter way of saying "print disk usage". It's all quick and easy when you know it, and very useful in this age of ever-increasing data volumes.
A quick way to create a blank text file
27th June 2008
The primary job done by the touch command in UNIX or Linux is to update the time stamps on files. However, it also has another function: creating an empty text file where you are "touching" a file that doesn't exist. This has its uses, particularly when you want to reduce the amount of pointing and clicking that you need to do, or you want to generate a series of empty files in a shell script. Whatever you do with it is up to you.
Quickly surveying free disk space on UNIX and Linux
21st June 2008
Keeping an eye on disk space on a Solaris server is important for me at work, while keeping the same top level overview is good for my use of Linux at home too. Luckily, there's a simple command that delivers the goods:
df -h 2>/dev/null
The df -h piece is what delivers the statistics while the 2> /dev/null rids the terminal of any error messages; ones stating that access has been denied are common and can cloud the picture.
A pleasant surprise…
4th December 2007
Yesterday, when taking the screen grab for my post on Quanta Plus, I did the Alt + Print Screen shuffle as usual. However, when I did so, I was greeted with a dialogue box asking me where I wanted to store the PNG file that was to be produced and what I wanted to call it. The operation was as swish as that. On Windows, the screenshot gets stuffed into the clipboard for you to extricate it with your graphics editor of choice, so this was an interesting surprise. It's the sort of thing that can make a good impression, and it is striking that Linux seems to be ahead of Windows on this one. Who said Linux was less than user-friendly?
Why I will be keeping Windows close to hand for a while to come after a switch to Linux
2nd December 2007
Even though I have moved to Linux, and it has been fulfilling nearly all of my home computing needs, I do and plan to continue to retain access to Windows courtesy of virtualisation technology. Thought keeping current with the world of the ever pervasive Windows is one motivation, there are others. In fact, now that Windows is more of a sideline, I may even get my hands on Vista at some point to take a further in-depth look at it, hopefully without having to suffer the consequences of my curiosity.
Talking of other reasons for hanging onto Windows, listening to music secured by DRM does come to mind. DRM is seen in a negative light by many in the open-source world, so Linux remains unencumbered by the beast. That isn't necessarily a bad thing, and the whole furore about Vista and DRM earlier this year had me wondering about a Linux future. However, I have been known to buy music from iTunes and would like to continue doing so. Though WINE might be one way to achieve this, retaining Windows seems a sounder option. That way, I am saved from having to convert my protected music files into either Ogg Vorbis or FLAC; the latter involves a lossless compression unlike the former, so the files are bigger with the additional quality that an audiophile would seek. MP3 is another option, yet there are those in the Linux world who frown upon anything patented. That makes getting MP3 support an additional task for those of us wanting it.
In my wisdom, I have succumbed to the delights of expensive web development tools like Altova's XMLSpy and Adobe's Dreamweaver. While I have found a way to get Quanta Plus to edit files on the web server directly and code hacking is my main way to improve my websites, I still will be having a bimble into Dreamweaver from time to time. I have yet to see XMLSpy's grid view replicated in the open-source world, so that should remain a key tool in my arsenal. While I haven't been looking too hard at open-source XML editors recently, there remains unexplored functionality in XMLSpy that I should really explore to see if it could be harnessed.
While I have included implicit references to this already, it needs saying that keeping Windows around also allows you to continue using familiar software. For some, this might be Microsoft Office, but OpenOffice and Evolution have usurped this in my case. Photoshop Elements is a better example for me. Digital transfers from scanners and DSLR's will stay in the world of Linux, while virtualisation allows me to process the images in whatever way I want. For now, I might just stick with the familiar before jumping ship to GIMP at some point in the future. With all that is written on Photoshop, having it there for learning new things seems a very sensible idea.
While open-source software can conceivably address every possible, there are bound to be niches that remain outside its reach. I use mapping software from Anquet when planning hillwalking excursions. It seems very much to be a Windows only offering and I have already downloaded a good amount of mapping, so Windows has to stay if I need to use this and the routes that I have plotted out before now. Another piece of software that finds its way into this bracket is my copy of SAS Learning Edition; there are times when a spot of learning at home goes a long way at work.
So, in summary, my reasons for keeping Windows around are as follows:
- Learning new things about the thing, since I am unlikely to escape its influence in the world of work
- Using iTunes to download new music and to continue to listen to what I have already
- Using and learning about industry standard web development tools like Dreamweaver and XMLSpy
- Easing the transition, by continuing to use Photoshop Elements, for example
- Using niche software like Anquet mapping
Though I suppose that many will relate to the above, Linux still has plenty to take over some of the above. In time, DRM may disappear from the music scene and not before time; accountants and shareholders may need to learn to trust customers. NVu and Quanta Plus could yet usurp Dreamweaver, and there may be an open-source alternative to XMLSpy like there is for so many other areas. The Photoshop versus GIMP choice will continue to prevent itself and all that is written about the former makes it seem silly to throw it away, however good the latter is. Even with changing over Linux equivalents of applications fulfilling standard needs, it still leaves niche applications like hillwalking mapping and that, together with the need to know what Windows might offer in the enterprise space, could be the enduring reasons for keeping it near to hand. That said, I can now go through whole days without firing up a Windows VM, a big change from how it was a few months ago. Still, I suppose that it's all too easy to stick with using one operating system at a time, which is Linux for me these days.