I created a server using c++ and want to run this server as daemon on linux..
How do I do this?
Thanks in advance...
There are many ways to daemonize a process. It is quite common that server implementations provides a switch to daemonize it at startup.
If you do not wish to implement such a feature, command-line tools exists such as this one : http://software.clapper.org/daemonize/.
I don't mean to sound condescending but did you try a google search, there is a heap of info on this out there, the first link I found: (http://www.enderunix.org/docs/eng/daemon.php)
You can use dup2() on Linux to make the FD's a bit easier to handle.
You may also want to look into using something like inetd to manage your server
Related
If it's possible, I'm interested in being able to embed a PostgreSQL database, similar to sqllite. I've read that it's not possible. I'm no database expert though, so I want to hear from you.
Essentially I want PostgreSQL without all the configuration and installation. If it's possible, tell me how.
Run postgresql in a background process.
Start a separate thread in your application that would start a postgresql server in local mode either by binding it to localhost with some random free port or by using sockets (does windows support sockets?). That should be fairly easy, something like:
system("C:\Program Files\MyApplication\pgsql\postgres.exe -D C:\Documents and Settings\User\Local Settings\MyApplication\database -h 127.0.0.1 -p 12345");
and then just connect to 127.0.0.1:12345.
When your application quits, you can always send a SIGTERM to your thread and then wait a few seconds for postgresql to quit (ie join the thread).
PS: You can also use pg_ctl to control your "embedded" database, even without threads, just do a "pg_ctl start" (with appropriate options) when starting the application and "pg_ctl stop" when quitting it.
You cannot embed it, nor should you try.
For embedding you should use sqlite as you mentioned or firebird rdbms.
Unless you do a major rewrite of code, it is not possible to run Postgres "embedded". Either run it as a separate process or use something else. SQLite is an excellent choice. But there are others. MySQL has an embedded version. See it at http://mysql.com/oem/. Also several java choices, and Mac has Core Data you can write too. Hell, you can even use FoxPro. What OS you on and what services you need from the database?
You can't embed it as a in process type thing like sqlite etc, but you can easily embed it into your application setup using Inno setup at http://www.innosetup.org. Search their mailing list archive and you will find someone did most of the work for you and all you have to to is grab the zipped distro and you can easily have postgresql installed when the user installs your app. You can then use the pg_hba.conf file to restrict the server to local host only. Not a true embedded DB, but it would work.
PostgreSQL is intended to run as a stand-alone server; it's probably possible to embed it if you hack at it hard and long enough, but it would be much easier to just run it as intended in a separate process.
HSQLDB (http://hsqldb.org/) is another db which is easily embedded. Requires Java, but is an excellent and often-used choice for Java applications.
Anyone tried on Mac OS X:
http://pagesperso-orange.fr/bruno.gaufier/xhtml/prod_postgresql.xhtml
http://www.macosxguru.net/article.php?story=20041119135924825
(Of course sqlite would be my embedded db of choice as well)
Well, I know this is a very very very old post, but if anyone has nowadays this question, I would refer to:
You can use containers running Postgres. Here's a post that could be helpful, doing something along this line using R:
https://rsangole.netlify.app/post/2021/08/07/docker-based-rstudio-postgres/?utm_source=pocket_mylist
Take a look at duckdb https://duckdb.org/docs/installation/ It is relatively new and still needs to mature. But it works pretty much like an embedded database ("In-process, serverless"), with bindings for several languages (Python, R, Java, ...)
I put this question on stackoverflow, because I found lots of quesions on the topic here already.
Short introduction
Simply put, nohup can be used to run apps in the background and keeps them running after the user logs off or the terminal or ssh session is closed e.g.
There are many example quesitons here on stackoverflow, like this or that.
My question is simple.
Why opt for nohup, when there are options like upstart, systemd, ... which manage the app as service in a much more convenient way (runlevels, ...)?
Reading the many questions on similar topics, the only option seems to be nohup. Almost never the answer is something like: "... use an upstart script, so it is all handled for you..."
I would mainly go with e.g. upstart, except maybe for a quick and dirty test scenario.
Am I missing something important?
nohup is quick, easy, doesn't require root access and doesn't make permanent changes in the system. That's why many people use it (or try to use it) instead of configuring services.
Running things in the background without any supervision is usually a bad idea, although there are many legitimate use cases which don't fit traditional service model. For example:
Background process might be needed only sometimes, after certain user actions.
More than one instance might be needed. For example: one per user or one per session.
Process might not need to to be running all the time. It just quits after doing its job.
Some real world examples (which use something like nohup and would be hard to implement as system services):
git will sometimes run git gc in background to optimize repository without blocking user work
adb will start its service in background and keep it running until user asks to terminate it
Some compilers have option to keep running in the background to reduce startup times of subsequent invocations
Your understanding is correct, the way those questions were asked the natural answer is nohup - upstart would be the answer to a different question such as How to make sure an application keeps running on Linux
I am writing some webservices in Go on a linux machine, so the Go executable needs to keep running
which is the best way to do it?
should I setup the Go executable as a service on the linux machine?
many thanks
The short answer: use the system service manager if you want to keep things super-simple. CentOS currently uses Upstart, and it's well documented and can handle most Go applications without too many problems. There are some good examples of Upstart + Go here and here
The long answer: personal preference. Supervisord, Monit and Circus are good options as well, but bring differing levels of complexity. I personally like supervisord, since it has a fairly clear syntax and a good heap of options.
There's also a good run-down here: http://tech.cueup.com/blog/2013/03/08/running-daemons/
I want to write a shell script for getting NTP(Network Time Protocol) info for debian server.
How can I write, I don't know ?
Why are you writing your own? There are lots of existing tools to do this. openntp is one example. Look in aptitude.
Is there a reason you can't use the existing tools?
You probably want to take a look at ntpdate manpage for details on how to use this command.
I'm using OpenOffice as a daemon. Sometimes, when the daemon is running a long time, CPU use spikes very high and then openoffice crash. At this point, the open office applicattion don't work and the documents don't be generated.
How can I restart automatically the openoffice daemon when this problem happens? Is there any way to monitor the service or to program a watchdog to handle it?
Thanks in advance, regards.
You may wish to use your distribution's services mechanism; Ubuntu and Fedora, for example, use upstart. Writing an upstart configuration file for your service probably wouldn't be too difficult.
If your distribution doesn't use upstart, you could either run it directly out of your /etc/inittab or use daemontools to monitor your service. (The linux-ha project also has some service monitoring tools, but may have more setup-requirements than you're interested in.)