Options to configure a Linux box from Java

Question

I'm trying to make an java application to manage Linux servers from a web interface. It is a bad idea to perform each task by calling bash shell ? Are there any other options other than those to use C, Perl or another language?

Answer 1

You could certainly do it that way. Ideally you'd open up a port and accept specially crafted, specific actions which perform only the intended actions (an interface server) through a socket library.

Answer 2

It's not necessarily a bad idea to use bash to do the actual work. It would help if you gave us more of an idea what exactly the web interface was changing.

Java in particular does not provide much system-specific controls, because it was designed as a cross-platform language, so putting specific platform tools in would go against it's purpose.

Answer 3

I should think that the disadvantage(s) of calling Bash scripts for your commands is all related to error handling and return values. Each of your Bash scripts will need to return sensible, useful information to the Java app in the case of failures (or even successes). And you'll probably want a common interface for that such that each Bash script, no matter its function, returns the same types so that the Java can interpret it easily.

So, in that sense, making the changes from your Java program reduces the complexity of handing the information back and forth. On the other hand, if Bash is easier for you, you may find it more fast and flexible.

Answer 4

Opening up a single bash shell and sending commands (and properly parsing results) shouldn't be bad. It does tie your program to a single OS and even a single shell, but that's the nature of what you are trying to do.

What I wouldn't do is open a shell for each command and close it after each result. It seems to me that would cause unnecessary thrashing when many commands were executed in a row.

Answer 5

Security concerns jump at me. If you have a form like "type command" then someone clever could exploit some things. For example "configure network" is fine but "configure network; install rootkit" can be typed because a semi-colon allows commands to be chained.

All in all, this is not tight integration. If this is a personal project, go for it. It's a good learning project to turn a procedural script into a java program. If this is a serious effort to recreate the many various webapp admin tools there are, I'd seriously suggest skipping this. The VPanel/CPanel things I've seen I hate. There used to be a php based linux admin thing that looked ok but I just find them easily to learn, easy to outgrow because the net and community is full of command line knowledge.

If you are trying to automate a large deployment, look at the ruby-based puppet. It looks really neat.

Answer 6

I have a socket server were I perform different operations (using ifconfig by calling shell for example) and I plan to integrate an client in a JSF application.Because I'm not experienced ant I intend to make it my graduation project, but I'm not so sure if calling bash from java to configure a linux box is a good solution.

Answer 7

A lot of the response would depend on why you're doing this and why other more obvious solutions aren't possible. Knowing why you would choose to roll your own as opposed to installing Webmin would be good, or why you're choosing to use Web UI at all as opposed to VNC to control the box. There are some obvious responses to the later (firewall issues for instance), but there's no immediately obvious reason for the former. Without knowing more about the requirements, answering questions about implementation details like bash scripts versus perl or C is meaningless.

Answer 8

1. Java does have some Linux-configuring classes (well, at least, OpenJDK does). Check OperatingSystemMXBean or something like that.

2. You're beter to write your own server configuration utility in the language you prefer, sanitize it, make it secure and then call it via bash from your java app.

Answer 9

There are two questions here:

1. Should you try to do the configuration work in Java, or should you externalize it?
2. Assuming that you have externalized it, should you use bash scripts.

In this case, the answer to question 1) depends. This kind of thing can be difficult to implement in pure Java. This leaves two choices; externalize the task using a Process, or try to do it in a native code library via JNI or JPA. The latter approach is complicated and gives you JVM crashes if you make a mistake, so I would rule that out.

On the other hand, if you can find a good standard or 3rd party Java API that does what you need (without infesting your JVM with flakey JNI, etc), you should use that.

The answer to 2) is that bash scripts will work as well as any other scripting language. I think that using scripts gives you a bit more flexibility. For example, if you need to do things to compensate for differences in the different flavours of Linux, UNIX or maybe even Windows (!) you can put this into the externalized scripts. (A corollary is that the scripts need to be configurable, so don't embed them in your source code!)

Another alternative might be to run the commands (e.g. ifconfig) directly, using a fully qualified command name and supplying the arguments as an array of strings, etc. But unless your app is going to run the external command 100s of times a minute, it is probably not worth the (Java) coding effort and the loss of flexibility / configurability.