I'd like to trigger file system events on a Linux virtual machine (VirtualBox). I'm not sure how to approach this, but I can imagine there could be 2 ways of doing it:
with a built-in command in the guest system
or from the host system controlling the guest through VirtualBox commands
I did some research and found tools like guard/listen, but I could not manage to make them work. (Guard asking for plugins and the documentation is not clear to me...)
My goal is not a new thing, I'd like to forward file system events from the host to the guest. On the host side I'm using fswatch to hook up to file system events. Fswatch would run a script on the guest system via SSH - that script/command could trigger an fs event in the guest system based on the parameter from fswatch which was a path... It's not an efficient approach I guess but for development purposes when I modify some files in the IDE should be good enough.
This one solved my problem: vagrant-notify-forwarder
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I am wondering if it is possible to write a program on Windows that communicates with a program within a Linux Virtualbox on the same machine. If this is possible, what is the best approach to doing this? Is there a way to do this without using the internet to communicate?
I found instructions showing how you could potentially use SSH, but I have never tried doing this before, so I do not know if using SSH to communicate would be the best option.
I was going to put this as a comment to a very vague question, but then it got too long.
It depends what you mean by "communicate"....
If the Windows machine should start a program on the Linux VM, you probably want plink.exe - see here.
If you want to transfer whole files, you probably want scp or FTP or FileZilla - see here.
If you want to send small messages occasionally, maybe netcat, also known as nc - see Netcat Cheatsheet here.
If you want full-on, high speed, continuous messages, maybe sockets or some messaging protocol like mqtt.
If you want to share data structures, like lists, queues or sets, you could allow both Windows and the Linux machine to access a shared Redis database - see here.
Or maybe it is enough to share a filesystem between the two machines - in which case you can make a Shared Folder in VirtualBox on your host and the VM can just mount that and read/write it. See diagram:
I am trying to run my application directly from the linux kernel(without usage of cron or something like that). If I change ./init/init.c, it runs too early:
$ dmesg
...
[ 0.605657] TEST!!!
...
My idea is to launch an application after successful user login, but I can't find an appropriate function to use.
You're jumping to conclusions. Why do you want the kernel to do anything if you have the whole userspace running already? (you want it on user login)
Have a look at one of the standard mechanisms for this (depending on what's available in your system):
systemd user sessions
.profile / .xinit files for users
For advanced scenarios, maybe even socket activation for services.
I was wondering if i can run a exe with daemons in mac and linux or do you have any other solutions to do something similar to a windows service that is a scheduler ? I know i can use crontab but i was wondering if there was other way to do it.
Thx
On OS X, the preferred way of doing things like this is with launchd daemons. You create a .plist file with information about what program to run, parameters to pass it, and what conditions to start it under (i.e. at certain times, when a network connection is received on a certain port, or just run always), and various other options. Lingon provides a handy GUI for creating the .plist, or just read the Apple LAUNCHD docs and create it yourself. Put the .plist in /Library/LaunchDaemons, and either reboot or activate it with sudo launchctl load /Library/LaunchDaemons/whatever.plist.
A warning about using launchd: most daemon-type programs for unix will "daemonize" themselves -- they drop into the background, and generally detach themselves from the program that started them. Launchd doesn't like this. It wants to keep watch over its children, so that it can monitor their status, relaunch them if necessary, etc. So you may either need to tell the program not to daemonize, or add an option to the .plist to tell launchd not to freak out if the program appears to quit.
Linux alternative to windows NT services are daemons. You can read a little more about it
here.
You also start executables by scripts located in "/etc/init.d" Just look at one of those scripts for reference. If you want to make a task or executable start at a given time use a crontab. It is made for this purpose and I don't see why use something else.
If you have a mono executable probably the easiest way is just to make a script in "init.d" if you want to start when system starts or make a crontab entry. It is realy easy. Here you can find a simple reference.
I have written a daemon in linux for doing dhcp for an embedded system. This platform only has a linux kernel running on it and have no CLI support. What is the best way for me to test my daemon? How do I write a program that will call the main function in this daemon and verify if its working fine?
Appreciate the answers.
When I've been in a situation like this, I've written a second daemon (or had a second listener in the existing daemon) to take the place of a CLI, listening at a particular port and responding to a very limited command set of your own choosing.
In this case, all you really care about is triggering the function on demand, so you could even have it trigger when you connect to this second port, and then report results back to the socket.
I strongly recommend, by the way, making sure your embedded system has some more generic mechanism for logging information to persistent storage and retrieving that log. It doesn't have to be syslog or anything so complicated. But you will want that ability in the future to enable forensic analysis of problems in the field.
You will want to write and debug your daemon in a full featured environment first, then install it on the embedded system at the end when you are sure it works properly.
If you can build a dhcp server for the embedded system you can surely build a simple shell for it also. Try building BusyBox or ash or dash.
You could also try using GDB remote debugging. I found an article about it.
How can I set Linux environment variables remotely from a Windows application?
You can't directly. Environment variables are just a table of values associated with the process, and inhereted when you fork(2) a process.
If you want to set them, you need some kind of code at the Linux side doing it. The simplest is probably to run your remote programs through a shell, and set them on the command line.
Otherwise, you need a way to get your Linux-side client to put them into the environment with setenv(3).
Taking your rather terse question at face-value, you could have your Windows application ftp to the linux system as the user who is going to run the linux app and modify their .cshrc or .bashrc, adding the desired environment variables to the shell script. This won't modify already-running shells, though.
At an abstract level, you're talking about inter-process communication. You have information in the Windows application you want to communicate to communicate to some Linux application. I'm not sure environment variables are the best way to communicate this data. Perhaps opening a socket between your Windows app and Linux app would be best.
Two ways I can think of - in probable order of simplicity:
Write a Linux program that listens on a network socket for commands. Your Windows app sends the appropriate command. The Linux program runs the command to set the environment variable - something like system(export MY_ENV_VAR=abc). This won't be secure over the network unless you make it so.
Use SSH to login to the Linux system, then run a script to set the variable. I don't know if there are SSH libraries around for Windows but I'd be surprised if there aren't. PuTTY is an excellent open-source Windows SSH client so you may be able to use code from there but you should check the license first - depending on how you plan to use your application. This option has the benefit that you can use PKI to secure the network connection, if necessary.