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Designing Good Linux Applications
An Anonymous Coward writes: "A guy from IBM's Linux Impact Team in Brazil has written a guest column on Linux and Main describing how applications should integrate with Linux. It's Red Hat-centric, but there is a lot of material about the FHS and LSB that most users probably don't know."
From the article:
I understand that this is directly from the FHS, and not some evil concoction from the mind of the author, but dammit, I think it's wrong. Perhaps /usr/local is obsolete with respect to package managers, and that makes some sense (because the package manager should handle proper management of placed files, though in practice that's not always the case), but as long as open source is around, there will always be software that is compiled rather than installed through a package manager. There will also always be applications that are not distributed in your package format of choice (as long as there is more than one package management system, this will always hold true). In these cases, it's still a good idea to keep around /usr/local and /opt. Personally, I'll have /usr/local on my systems for a long time to come, because I prefer to use the Encap management system.
Designing Good Linux Applications
The 'Linux' word is completely unnecessary - "Designing Good Applications" should suffice.
Application design couldn't care less of the OS that the application is planned to run on.
Documentation in
There will be things you don't like about the LSB and FHS. Personally, I reckon initscripts aren't config files and should live in
IMHO, to attract OSS developers, a piece of software has to be:
By any way, I don't pretend that these are anything more than a few rules of thumb, but in the end I'm sure that, for OSS software having the characteristics above, developers willing to do maintenance will show up by themselves without needing to preach them.
Ditch the concept of spreading pieces of your app all around the FHS. This is organizationally similar to Microsoft's registry. It becomes a maintenance nightmare. Yes, RPM keeps track of some pesky details that let us get away with a messier install. Yes, the FHS does impose a common structure on what is an otherwise unstructured mess. But programmers are human beings, subject to the whims of ego, ignorance, and yes, even creativity and sheer brilliance. We're going to deviate from the suggested standards if given the opportunity, for one reason or another.
Give me one main point of access to everything the application does. If you need to use config files, give me the option of manipulating them through the application itself, preferably in the context of my current task. Give me one place to go looking for all the bits and pieces of the app. No, the FHS isn't simple enough. Give me context-sensitive documentation so I don't have to wander outside the app to get my job done. Don't make me wade through a spaghetti-code config file, with the documentation propped open on a separate screen to keep from getting lost.
Programmers are lazy. I should know, I am one. The last thing I want to do when I'm getting ready to release a program to non-techie users is tie up all the loose ends that seem ok to me, but not to the non-techie user. I'd rather document how to get a tricky task done than write the code that automates the tricky parts. I'd rather tell the user how to go tweak the flaky data in the database by hand than add another error-correcting routine. And it's more work to give the user one simple, full-featured point of entry to each piece of a complex application. But that additional work will make the application more usable, for the expert and the novice alike.
/opt is in FHS 2.2 at secton 3.12. It begins:
Doesn't look very depricated to me. I think the problem is your FHS link isn't really the FHS; it is the SAG (Systems Administrator Guide), which in section 4.1 clearly says it is loosely based on the FHS.
As for /usr/local, I do agree it should be off-limits to the distribution (besides setting it up if not already present). And packages in the package format of the distribution (e.g. RPM for Redhat, Mandrake, SuSE, etc ... DEB for Debian and any like it ... TGZ for Slackware ... and so on) really should stay out of /usr/local. What /usr/local should be is whatever is local policy (FHS doesn't say it this way). Packages that the administrator really wants to be separate from the package management system, stuff compiled from source, stuff locally developed, all is eligible to be in /usr/local. My guess is the author of the article has no experience doing system administration combined with a decision making role where he might have to choose to do something slightly different than what everone else does.
now we need to go OSS in diesel cars
That's not the solution to the problem. Any management system ceases to become effective as soon it ceases to be ubiquitous. If your Apache is locally built, and you made the mistake of not packaging it, then you've nullified the effectiveness of the package manager for anything which touches apache.
You say the system administrator should know how to package applications? Why the system administrator? I'd have thought you'd have expected the programmer to do that.
Good point - ideally the programmer should, but its a simple enough case for SysAdmins to learn if they do encounter an unpackaged app.
Have you tried making RPMs? I'm not a programmer by any means but its amazingly simple. Check www.freshrpms.net for a few good tutorials.
Also, some "dependencies" are option, and don't need to exist unless a feature is to be used that needs it. For example, if I'm not using LDAP for web site user logins, why would I need to make sure LDAP is installed if some module that would otherwise use it is smart enough to work right when I'm not using LDAP.
Another good point. This should be handled by a system similar to debs excellent required / suggested / recommended dependency system, which could fairly easily be ported to RPM from what I understand of it.
Finding out a dependency exists when something breaks is no way to manage a system. Knowing what software has been installed on a machine is vital tomaintaining the security of your machines, and having proper uninstalls stops your hard disk from filling with crap. And there's a stack of other benefits.
I find most people who dislike RPM haven't used the system. its very much similar to building an app. Inside the RPM itself is the original tarball of the app (plus maybe a couple of patches) and the spec file which is comprised of:
Its pretty muc hthe same as if you'd compiled the app without a package manager. RPM just standardizes your build process. You can easily rebuild source RPM for your local architectecture, and RPM will take compiler flags for your own custom configuration options. I like compiling a lot of apps from source too: I just take a few extra moments do it in a standardized fashion. This pays off repeatedly when I'm administering the machine infuture (or if I need to repeat thsi work on another machine).
It's the creation of the spec file that's a chore. I have to know what dependencies the package has to make it. If I know already, such as by RTFM's the original source package docs, then I know all I need to know to manage it without RPM. I still see making an RPM here as a redundant step.
I do some programming, but I still don't RPM-ify those programs ... yet. But when someone comes up with an "autospec" "autorpm" program which figures out everything to make the RPM file so it becomes as trivial to make it as to install it, I might be more interested. Right now I'll still with "./configure" and "make install" which work just fine for me.
now we need to go OSS in diesel cars