Help needed understanding abns@XXXXX

Please can someone explain, or point me in the right direction to understanding Abstract Name Sockets as used in Haproxy.

I see many references in haproxy.cfg posts with entries like


But I have no idea where the string after the @ is coming from.
It may be that people are posting truncated haproxy.cfg configs, so I can’t understand it.
Or these are defined somewhere (on a Linux Server) outside of haproxy.cfg.

Reference used:

Those configurations are complete.

Like unix domain sockets, abstract name space sockets are just another type of sockets, which you can bind and connect to.

For example, in this haproxy configuration the backend verif-none accesses a frontend fe-ssl-normal of haproxy itself:

backend verif-none
 server recir abns@haproxy-normal

frontend fe-ssl-normal
 bind abns@haproxy-normal

The same could be done with a unix socket:

backend verif-none
 server recir /var/haproxy-normal

frontend fe-ssl-normal
 bind /var/haproxy-normal

Or, of course, a IP socket:

backend verif-none
 server recir

frontend fe-ssl-normal

Unix sockets, because they are actually in the filesystems, have some challenges with permessions, chrooting and chowning (when haproxy is dropping privileges). Abstract name space sockets are simpler to handle because filesystems permissions are not involved.

Think of it as a replacement for a sockets on free ports on

For example in the configuration you linked, put it into a text editor and:

  • replace abns@haproxy-normal with
  • replace abns@haproxy-clientcert with
  • replace abns@haproxy-tcp-normal with
  • replace abns@haproxy-tcp-clientcert with
  • replace abns@haproxy-error with

and the config as well as abns sockets will start making sense. It’s just a quite complex haproxy configuration so it’s not ideal to use it to learn about abns or unix sockets for the first time.

Thanks very much for your detailed explanation…
It took a number of reads before I got it!
It never occurred to me that a backend could feed a frontend. Now I understand the reason some examples refer to them as loopbacks.
Since we wrote, I’ve now seen examples of Unix and IP Socket methods
Thanks again

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