I need to detect whether NFS is installed or not on the running server in my Ruby code.
If there is any way I can do this in cross-platform way(or at least in unix/linux)?
I can't think of a cross platform way to do it as there's no standards for getting kernel info. I think it would have to be specific to the guest OS type. Linux you could do "modinfo nfs". Solaris boxes you could also use modinfo and search for nfs in the output or look in /etc/dfs/fstypes. Using "uname -s" will tell you which method to use.
Related
I want to study the kernel of Linux without any distribution.
I found the LoadLin boatloader of Ms-dos, but i think it works only in older version of windows (windows 95,98, ME).
So i need to install the kernel only in my PC if Possible.
How I can install it?
The kernel only is not that much useful to you; you'll probably need some shell and a working compiler if you want to test things first-hand, and these are not part of the kernel.
There's a distribution called Linux From Scratch which basically allows you to install the kernel and then whatever other stuff you want, literally from scratch (as in, by compiling stuff yourself and only adding what YOU want)
I am wondering though, what is it exactly you want to study and how does having a distribution affect your studying of the kernel? (Yes, some distributions ship custom kernels but the major features are almost always the same)
Minimal Linux Live is a small script that:
downloads the source for the kernel and busybox
compiles them
generates a bootable 8Mb ISO with them
The ISO then leaves you in a minimal shell with busybox.
With QEMU you can then easily boot into the system, which might be a more convenient way to study the kernel.
Or you can just use the Live ISO as a regular distribution and install it on metal.
Usage:
git clone https://github.com/ivandavidov/minimal
cd minimal/src
./build_minimal_linux_live.sh
# Wait.
# Install QEMU.
# minimal_linux_live.iso was generated
./qemu64.sh
and you will be left inside a QEMU Window with you new minimal system. Awesome.
See also:
https://unix.stackexchange.com/questions/17122/is-it-possible-to-install-the-linux-kernel-alone
https://superuser.com/questions/307087/linux-distro-with-just-busybox-and-bash
Why not use a distribution? Just get some free VM (eg. virtualbox) and install an arbitrary Linux distribution. You have all the build tools there you need to compile the kernel, without actually touching your system.
Forgive my ignorance: I need to use a library that requires a UNIX system (LIBSHORTTEXT). Do I need to install a virtual machine with Unix or is Cygwin enough? (I've read quite a few articles about the difference between them but I don't really understand the practical difference for this specific use). Thanks!
Edit: The documentation that said that the library needs UNIX is here
That really depends on what makes the library "require UNIX". Looking at it briefly, it appears to be ANSI C and Python, both of which should either compile or be fairly easy to port on a Windows development system. In your case I'd go with Cygwin if you don't already have a development suite running, as it is likely to allow you to just get things running.
A Virtual Machine is a bit more compartmentalized, so much less connection between Windows and the running software. Unless you are planning to use the operating system in the Virtual Machine as a target for your program, it is a bit of overkill in this case, IMHO.
Hope this helps.
Normally I would say Cygwin will do, but it depens on how you use the library. And when you say that the library requires a UNIX system what do you mean? Are you building a python or c++ program?
The main difference between working in cygwin and a VM is that cygwin is still working in a windows environment with windows directories and hardware drivers, whereas a VM have all this emulated as if it actually was a UNIX machine.
Windows has a application-virtualisation tool called App-V.
Linux appears to have a similar tool called Docker.
My question is - is there a Docker equivalent for MacOS X? (ie without having to spin up a Linux virtual machine on VirtualBox?)
There is no strict analog for OS X. If you are against spinning up a virtual Linux machine, your options are:
A simple chroot jail. The jailkit utility can help you out with this.
For your own OS X applications, using App Sandbox to limit the resources your app has access to.
Again, neither of these is just like Docker 0.x, which uses LXC under the covers.
The chroot solution is closer, since it is one of the components that LXC is built on. However, it doesn't provide kernel namespaces or anything like cgroups — both of which are two very important parts of LXC.
I have a device driver that is freezing the OS. The mouse wont even move. I am trying to debug this issue and I believe one good approach is to use gdb with qemu, two things I have never used before. Is there a better approach?
So first I need to compile the kernel with debug symbols which I have done already.
Now, there is a new file that is generated called vmlinux that is located in that same folder as the source. It seems that I also need a bzImage file according to this so I can run the newly compiled kernel using:
qemu-system-i386 -kernel bzImage
or in debug mode
qemu-system-i386 -s -S -kernel bzImage
I cannot locate the bzImage file. Where do I find it or what is missing here? Is the bzImage referring to the OS Image I created using qemu-img create?
Also, what I do not understand is that now the kernel is compiled (vmlinux) how does I run it with qemu? So my question is when I run it with qemu or the debugger is the kernel running as an app in my main OS?
also how can I install my device driver? My understanding the kernel is not Ubuntu so there is no UI?
Also, I installed qemu and when I type qemu I get command not found. I am guessing I have to pick a specific processor emulator as in qemu-system-i386, qemu-system-x86_64, or qemu-x86_64?
How is qemu different or similar to the kvm command?
Thanks.
So, if I understand the problem correctly, you have a kernel module that needs no specific hardware. When you are working with the module, the system freezes but the kernel log contains nothing special.
The following may be helpful.
Getting the log
The symptoms you described may still be a result of a kernel oops or panic. The logging facilities sometimes die before they can output the information about the error to the log file. You may try to output the log via a serial port, this should be more reliable.
As your kernel module does not need any specific hardware, the easiest way is probably to install the same Linux distro as you use to a virtual machine and connect the virtual serial port (COM) of that machine to a pipe on your host system.
This is usually quite easy to do. For example, this blog post contains the detailed instructions in case the host OS and the guest OS are Ubuntu 11.10.
VirtualBox is used there to manage the virtual machines. If you prefer QEMU, this should be possible as well. I suppose it is a bit easier to go with VirtualBox though but it is a matter of personal preference.
Basically, you need to perform the following steps.
Create a virtual machine and install the Linux distro you need as a guest OS there.
Enable a serial port (COM1, ...) in the configuration of the virtual machine and configure it to connect to a special file on the host ("host pipe"), say /tmp/vbox_serial.
Start the guest OS and adjust its boot options: at least, add console=ttyS0,115200 or something like that to the kernel options in the boot loader menu.
On the host, start minicom, socat or whatever else to read from /tmp/vbox_serial.
That is it. Now you should get the kernel log of the guest OS pouring to your host system via /tmp/vbox_serial. If the guest system crashes then, you will get the log even if it is not saved into a file on the guest itself.
To make things easier, you may use socat on your host system rather than minicom that the author of that blog post suggests. The power of minicom is probably not needed here.
This way, you can use socat and tee to save the log to guest.log file while still outputting it to the console:
socat /tmp/vbox_serial - | tee guest.log
If there was a kernel oops or panic, the backtrace in the log usually helps to find out what
has gone wrong.
Detecting Deadlocks
If you have obtained the full log via a serial connection or some other means and still there is nothing suspicious there and you suspect there has been a deadlock in the kernel,
lockdep tool may help. It is included into the kernel (but you may need to rebuild the kernel with CONFIG_LOCKDEP_SUPPORT=y).
Lockdep detects the potential deadlocks and outputs the results to the kernel log. This presentation may help you analyse its output.
Tracing Facilities
If you need tracing of some events in the kernel to debug your system, there are some tools that could be handy.
Kprobes - a kind of breakpoints you can set in almost arbitrary place in the kernel. Can be used to trace function calls among other things, with a moderate performance impact.
SystemTap - a powerful system to analyze what is going on in the kernel. Part of it is based on Kprobes.
Ftrace - a tracing system included into the kernel, incurs less overhead than Kprobes if that matters.
I am studying Linux driver programming and in it, it is recommended that I work on self-compiled Linux kernels and not any distributions. I have tried compiling Linux 2.6.9 in ubuntu but the process returns errors in 'make menuconfig' stage.
I would prefer to work with Linux in a virtual environment so that I can fearlessly experiment with the kernel. So, is there any way I can compile and run Linux in a virtual machine (say VMware installed on Windows)? I can use live CDs for the purpose of compiling the kernel.
So in short, please suggest, how can I compile, install and run Linux kernel in a virtual machine in an error-free way?
I searched and read this. But after following these steps when I restarted my computer there was no separate Linux 3.2.17 OS. But my ubuntu 12.04 was now showing 3.2.17 kernel. Although this is the first time I could compile a whole kernel on ubuntu without any error, I want to load that kernel on other partition and use it as an independent OS. So, if anyone can tell, what to do in addition to the steps in the tutorial so that I can achieve this?
The simplest thing to do is probably to install some Linux distribution on a VM, such as VMWare or VirtualBox, and continue from there. You could try using a live-cd, but I'm guessing that the lack of persistent storage might get irritating. There are, of course, ways around that, but installing some distribution is probably simpler, and you don't really need that much disk space for it if all you want to do is compile a kernel.
If all you want to do is compile a kernel module, and if you already have some pre-installed Linux environment, you should also note that modern Linux installations allow you to compile modules without the need to re-compile the entire kernel. You will need the kernel source and headers, though. See, for example, this document.
And BTW, speaking of modern kernels, why did you choose to use 2.6.9? It's almost 8 years old by now. Newer kernels might actually be easier to develop for. Also, there's no guarantee that
modules developed with such an old kernel would still work with current ones.
I suggest you to read this page. This document shows you how to boot your personal kernel on qemu and how to use the debugger on it.
Kernelnewbies is the right place to start kernel hacking. This website contains a set of rich tutorials about kernel hacking and tweaking just for newbie Linux developers. Also, you can join the community and start contributing to some tiny Linux projects.
For a quick start, follow the instruction from the "kernel first patch" tutorial. Since you're cloning the "origin" remote repository in this tutorial, you'll work on the latest branches of Linux kernel. So, there's no need to worry about working on an old version of Linux. Meanwhile, if you're not comfortable working with git trees, you can always download the latest version of Linux from front page of "kernel.org".