Here my first question :P.
I am developing some little projectes. I want to change dhcp server rules of IP/MAC without rebooting the server (In a dinamic infrastructure).
I think that the best solution is to use a dhcp server with a database backend, in order to change the SQL information (With an easy JDBC client).
But I want to know some suggestion about open Source Projects, or howto's that explain how to implement it.
Thank you very much
Usually on Unix, long running daemons listen for the HUP signal. On receiving that signal, they re-read their configuration files. This allows daemons to have no down time, but get updated configuration options.
The guys at ISC (authors of BIND and the ISC DHCP server) are working on KEA, a new DHCP server implementation that -- among other nice features -- has SQL support. The source code has had support for SQLite and MySQL for years, and PostgreSQL support was added recently.
There's no proper release yet, and very little activity on their dev/users mailing lists. Hopefully that will change as the code matures, releases are made, distros start packaging it, and it gains traction with users.
SpliFF
On Unix.
No, restart the DHCP server, no the machine :). Sorry.
Because when you change the dhcp.conf you need to restart the dhcp (dhcpd)
Related
Is it possible to migrate a single and particular TCP connection inside a running process in one machine to another machine using CRIU tools in Linux?
What I want is to dump a particular TCP Connection information in a memory and transfer this information to a peer machine. Inside this machine, I will use the dumped information to recreate the the migrated TCP connection. Does anyone have an example or tutorial in c language?
I am aware about different solutions like SockMi which provides Kernel Module + User Space APIs to migrate a certain TCP Socket. However, I want to use CRIU tools since it is part of Linux Mainline.
Right now we only have the TCP migration functionality integrated into CRIU tool. It sits in the sk-tcp.c file, the whole TCP-repair code is there, though it's bound to the rest of CRIU.
On the other hand, we've been asked for TCP-only migration for quite a while, it's possible to pull this code into smth like libcriutcp.so, but it will require patching. You're welcome to participate to the https://github.com/xemul/criu/issues/72
I am looking to develop a C implementation of a 9p file server on a Linux machine. There isn't enough documentation in the internet about 9p and I am not very experienced with implementing servers. My general design is as follows:
Use UNIX sockets to listen to incoming 9p messages.
Decode the 9p message and spawn a new thread to perform the required task.
Reply to the client with the appropriate 9p reply message.
The server would just live in the user space and it will translate the 9p messages into a UNIX call.
Do you see any problems or have any recommendations regarding the proposed design? Are there any documentations that you can refer me to that will help me? How do you think I should debug my server and make sure it is working correctly.
Consider libixp (MIT license).
I've played around with wmii and use it in everyday work. libixp was part of wmii (in the earliest releases) and now it is an independent project. Check wmii's early versions to get a good starting point or dive directly into libixp.
To debug your server just mount it with 9PFUSE(4) with parameter −D to print each FUSE and 9P message.
I am trying to create a client in C that will talk with a BACnet server. This BACnet server is stored on an industrial device (CAN2GO) and I am not sure how I could talk with this device.
I spent quite some time reading documentation for BACnet and I never found a clear example for a BACnet client. I already did some server and clients using TCP and UDP but I don't know how to start this BACnet client and I must say I am getting quite desperate.
I found a library which seems to correspond to what I want which is called BACnet protocol stack but when I tried the whois exemple no device was found (I expected to found the bacnet server but maybe I shouldn't ?).
So my question is : could you give me an exemple in C, or another language but C would be better, that would communicate with a BACnet server (nothing complicated just a question and analysing response). This example could be using the library I just wrote about or if you prefer another library I am of course open to everything.
Thank you very much for your time and answers.
I have used that stack and it is the best open source one you are going to find. If you cannot see anything using the demo\whois\bacwi example from that library, then there is something wrong with your setup. In particular, are you using IP? Are your BACnet client and BACnet server on different machines (they cannot be on the same without some serious tweaking)? Are the two machines on the same IP subnet? (They must be, once again, unless you do some serious tweaking (in this case, setting up BBMDs (BACnet Broadcast Management Devices))).
You will also want to try the "Read Property" example (demo\readprop\bacrp.exe) to actually read a value from the server.
If you are still stuck, then post your detailed problem at the link on Sourceforge, Steve, the author, is very responsive to questions.
I am currently using the stack - just started. I had a little trouble at first, not sure if my problem is the same but.. I basically am using some BAC components made from Schneider Electric (UNC-500) and an old un-supported platform (Niagara R2). On my laptop I created a host server and addressed it to a private LAN network between it and the UNC. My laptop was also using wifi, which was utilizing DHCP, so I had two separate interfaces going. This was my problem. I couldn't read or get 'I-AM' responses back from the UNC. As soon as I turned the WIFI off, I got the 'I-AM' broadcasts. Make sure that you are on the same network as your device, and that there are not other interfaces active. Maybe there is a way to assign the interface to use, IDK. I just started using it.
I am currently building a chat server (meebo style).
The architecture is something like this.
Bitlbee over libpurple is on host B. Its a trivial server on data center.
User communicates with bitlbee via web server (just like meebo) on Host A. The backend of this web server maintains chat session. It just translates the user commands to proper bitlbee comamnd and sends back to host A.
The most important part here is that host A will be deployed in embedded Linux.
I have 2 questions.
To keep the chat session persistent I am thinking of using node.js. As its much more easier to create a real time application with persistent connection. But I doubt if its supported in such platform.
If I use C instead of node.js (I am not using any web server) I can talk to the irc server at host A by libirc. But how do I implement all the web server features in C (like session, url/cookie/post data parsing etc) ?
Also if you think my approach is wrong or there is a better approach please tell me how can I improve this architecture?
Note: This is NOT a high volume chat server.
If building V8/Node.js is prohibitive on the embedded platform, the next best thing would be to take the event loop and platform layer (libuv) and HTTP parser (http-parser) of Node, both written in C and use those as a starting point. These are the same libraries used to build Node.js so they are battle tested and will give you the performance characteristics you seek.
Ryan Dahl, author of Node.js, demonstrates exactly how to use libuv and http-parser to build an asynchronous web server in C.
Put a ZNC server between Bitlbee and the web-based IRC client. Bitlbee will think that the user has never logged out and ZNC can maintain a backlog of messages until the user connects again with the web client.
I would try to go with node.js if that is your choice, also what embedded system is it? As knowing that would help more. Also, another plus for node.js is that it does have session handling built it, but if you wanted to do it in C try and see if you can get a sqlite wrapper running on the embedded device to store the session information.
But, if possible stick to something with less work on embedded devices, feels bad to reinvent a lot of stuff or have to fiddle with compile issues for your device.
In short: Is there any known protocol for remote process management?
I have a system that contains several applications, each has it's own computer in a local network. When the applications are up and running, they communicate without any problems.
What I'm interested in is a protocol to manage the remote applications startup, shutdown and monitoring. By monitoring I mean getting error codes (predefined) when something goes wrong. Ideally I would control the whole system from one managing application and get status about what's going on.
I once worked in a place that wrote an in-house protocol that did this. However, I wish to avoid writing it again if someone already figured this out.
Edit: some more details:
Platforms in use are Windows and Linux, both on x86.
On Windows, C/C++ and .NET are used. On Linux, C/C++.
Why bother with homegrown solutions instead of using tried and tested technology? Unless you only employ programmers who are MENSA members with 30+ years of experience, your solution will be less robust and costlier to maintain.
You failed to mention any details about the platform you're using, so I'll assume a Unix-ish system. I would go with (and have been going with for years)
SNMP for monitoring
either daemontools or cron + scripting (as a distant second choice) for supervision and restart
ssh/scp with RSA authentication for interactive intervention, remote command execution, and occasional transfers