Adventures & experiences in contemporary technology
In the world of UNIX and Linux, symbolic links are shortcuts but they do not work like normal Windows shortcuts because you do not jump from one location to another with the file manager’s address bar changing what it shows. Instead, it is as if you see the contents of the directory at another quicker to access location in the file system and the same sort of thinking applies to files too. In some ways, it is like giving files and directories alternative aliases. There are soft links that point to the name of a given directory or file and hard links that point to actual files or directories.
For a long time, I was under the mistaken impression that such things did not exist in Windows until I came across the mklink command, which came with the launch of Windows Vista at the start of 2007. While the then new feature may not be an obvious to most of us, it does does that Windows did incorporate a feature from UNIX and Linux well before the advent of virtual desktops on Windows 10.
By default, the aforementioned command sets up symbolic links to files and the /D switch allows the same to be done for directories too. The /H switch makes a hard link instead of a soft link so we get much of the functionality of the ln command in UNIX and Linux. Here is an example that creates a soft symbolic link for a directory:
mklink /D shortcut target_directory
Above, shortcut is the name of the symbolic link file and target_directory is the destination to which it links. In my experience, it works best for destinations beyond your home folder and, from what I have read, hard links may not be possible across different disks either.
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 starting automatically on there without success 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 and 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 seems 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 more information. There are references to an earlier release of Fedora but the content still applies to later versions of Fedora right up to the current release if my experience is typical.
The latest buzz surrounding Windows 7 has caused one observer to suggest that it’s about to blast Linux from the desktop. My experiences might be positive but 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 but 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 come across these before, they are a little hard to explain but it’s great to have 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. It’s true to say that Windows 7 gets Libraries but 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 and it’s when they get there that all of the fidgeting starts. The cause is the constant need for system monitoring and it eats up resources that could be used for other things. I know some packages are less intrusive than others but 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. I can see the reason for this in that it’s trying to hamper the attentions of nefarious malware but 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 going away and trying to guess what I need and getting it wrong, an experience that seems typical of Microsoft software.
Command Line
This is less of a miss than it used to be but 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 learning its ins and outs. It’s not a bad skill to have listed on the proverbial CV but I now know my way around bash and its ilk while knowing where to look when I want 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. I am not sure if I’d go acquiring the final version of Windows 7 but I am certain that it will not be replacing Linux as my main home computing platform, something that come as no surprise given what I have said above.
UNIX (and Linux) does a wonderful trick with its file and folder shortcuts; it effectively treats them as file and folder transporters that transfer associate a file or folder that exists in one folder hierarchy with another and it is treated as if it exists in that hierarchy too. For example, the images folder under /www/htdocs/blog can have a link under /www/htdocs/ that makes it appear that its contents exist in both places without any file duplication. For instance, the pwd command cannot tell a folder from a folder shortcut. To achieve this, I use what are called symbolic links and the following command achieves the outcome in the example:
ln -s /www/htdocs/blog/images /www/htdocs/images
The first file path is the destination for the link while the second one is that for the link itself. I had a problem with Google Reader not showing up images in its feed displays so symbolic links rode to the rescue as they did for resolve a similar conundrum that I was encountering when editing posts in my hillwalking blog.