Tag Archive for file system

Relocating the Apache web server document root directory in Fedora 12

April 9, 2010 No comments

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.

Linux, Security, Software, Web Development

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Seeing how things develop

October 7, 2009 No comments

One of the things that I do out of curiosity and self-interest is to keep tabs on what is happening with development versions of software that I use. It is for this reason that I always have a development version of WordPress on the go so as to ensure that the next stable version doesn’t bring my blog to its knees. There have been contributions from my own self to the development effort, mainly in the form of bug reports with the occasional bug fix too.

In the same vein, I have had a development version of Ubuntu installed in a VirtualBox virtual machine. There have been breakages and reinstallations along the way when an update results in disruption but it is intriguing too to see how a Linux distribution comes to fruition. In the early days of Karmic Koala (9.10), everything was thrown together more loosely and advances looked less obvious. It is true to say the ext4 file systems support was already in place but the interface looked like a tweaked version of the standard GNOME desktop. Over time, the desktop has been customised and boot messages hidden out of sight. Eye candy like new icons and backgrounds have begun to entice while other features such as an encrypted home folder, Software Store and Ubuntu One came into place. Installation screens became slicker and boot times reduced. All of this may seem incremental but revolutions can break things and you only have to look at the stuttering progress of Windows to see that. Even with all of these previews, I still plan to do a test run of the final revision of 9.10 before committing to putting it in place on my main home PC. Bearing the scars of misadventures over the years has taught me well.

Windows development is a less open process but I have been partial fo development versions there too. In fact, beta and release candidate installations of Windows 7 have convinced me to upgrade from Windows XP for those times when a Windows VM needs to fired up in anger. A special offer has had me ordering in advance and sitting back and waiting. With my Windows needs being secondary to my Linux activities, I am not so fussed about taking my time and I have no intention of binning Windows XP just yet anyway.

The trouble with all of this previewing is that you get buffeted by the ongoing development. That is very true of Ubuntu 9.10 and has been very much part and parcel of the heave that brought WordPress 2.7 into being last year. Things get added and then removed as development tries to fins that sweet spot or a crash results and you need to rebuild things. It is small wonder that you are told not to put unfinished software on a production system. Another consequence might be that you really question why you are watching all of this and come to decide that what you already have is a place of safety in comparison to what’s coming. So far, that has never turned out to be true but there’s no harm in looking before you leap either.

Blogging, Linux, Software, Virtualisation, Web, Web Development

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/sbin/mount.vboxsf: mounting failed with the error: Protocol error

April 19, 2009 10 comments

These times, my virtualisation needs are being well served by VirtualBox 2.2. It may be the closed source variant but I have no complaints about it. Along with a number Windows VM’s, I also have one running Ubuntu 9.04 and, for the first time, I seem to have VirtualBox’s Guest Additions playing with a Linux guest as they should. Even the Shared Folders functionality is working.

However, I did get one problem when I tried out the last feature for the first time. The procedure is to issue a command like the following in a terminal session after creating the requisite directory in the file system and adding a host directory as a shared folder:

sudo mount -t vboxsf Music /mnt/host_music/

Above, Music is the name of the folder in the VirtualBox manager and /mnt/host_music in the directory in the guest file system. However, this returned the message at the head of this post at that first attempt:

/sbin/mount.vboxsf: mounting failed with the error: Protocol error

The solution thankfully turns out to be an easy one: reinstalling the Guest Additions and that certainly did the trick for me. The cause would appear to have been an update to Ubuntu and 9.04 is understandably in a state of flux at the moment (I suspect kernel upgrades because of my previous experiences). Regardless of this, it is good to know that it’s a problem with a simple fix and I am seeing the niceties of a larger virtual screen system together automatic grabbing and releasing of the mouse cursor too. There may be a chance to explore the availability of these sorts of features to other Linux guests but I have other things that I should be doing and there’s sunshine outside to be enjoyed.

Linux, Virtualisation

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Work locally, update remotely

December 4, 2008 No comments

Here’s a trick that might have its uses: using a local WordPress instance to update your online blog (yes, there are plenty of applications that promise to edit your online blog but these need file permissions to the likes of xmlrpc.php to be opened up). Along with the right database access credentials and the ability to log in remotely, adding the following two lines to wp-config.php does the trick:

define(‘WP_SITEURL’, ‘http://localhost/blog’);

define(‘WP_HOME’, ‘http://localhost/blog’);

These two constants override what is in the database and allow to update the online database from your own PC using WordPress running on a local web server (Apache or otherwise). One thing to remember here is that both online and offline directory structures are similar. For example, if your online WordPress files are in blog in the root of the online web server file system (typically htdocs for Linux), then they need to be contained in the same directory in the root of the offline server too. Otherwise, things could get confusing and perhaps messy. Another thing to consider is that you are modifying your online blog so the usual rules about care and attention apply, particularly with respect to using the same version of WordPress both locally and remotely. This is especially a concern if you, like me, run development versions of WordPress to see if there are any upheavals ahead of us like the overhaul that is coming in with WordPress 2.7.

An alternative use of this same trick is to keep a local copy of your online database in case of any problems while using a local WordPress instance to work with it. I used to have to edit the database backup directly (on my main Ubuntu system), first with GEdit but then using a sed command like the following:

sed -e s/www\.onlinewebsite\.com/localhost/g backup.sql > backup_l.sql

The -e switch uses regular expression substitution that follows it to edit the input with the output being directed to a new file. It’s slicker than the interactive GEdit route but has been made redundant by defining constants for a local WordPress installation as described above.

Blogging, Web Development

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Removing files for which you have no write access from the GNOME Wastebasket in Ubuntu 8.04

September 2, 2008 No comments

It might be that GNOME contains a small trap awaiting the unwary: moving files for which you have no write permissions to the Wastebasket using Nautilus. This happened to me in Ubuntu 8.04 and I couldn’t clear the Wastebasket using the normal means. To resolve the situation, I thought of finding where the Wastebasket in the normal file system and that isn’t as easy as it might be. One place to look is ~/.Trash but I didn’t have that at all because the location in Hardy Heron is ~/.local/share/Trash/Files. Armed with this knowledge, I turned to the command line and performed the required erasure using sudo. It was all over very quickly once I knew where to look.

Linux, Software

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Watch where you store your virtual machines when using VMware on Linux

July 12, 2008 No comments

My experience is with Ubuntu on this one but I have found that you need to be careful as regards the file system used by the drive where you keep your virtual machines. If it is NTFS, VMware can fail to start a VM because it cannot create a virtual memory file while it presents as physical memory to a guest operating system. Use ext2 or ext3 and there should be no problem, even if that means formatting a drive to fulfill the need. That’s what I did and all was well thereafter.

Linux, Virtualisation, Windows

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