Apache HTTPD Running Out of Semaphores With Too Many Virtual Hosts and Proxies

Solution Verified - Updated -


  • We are running Red Hat JBoss Core Services Apache HTTP Server on RHEL 7.9 as a balancer proxy. With 6 or fewer vhosts system runs as expected. With 7 or more vhosts Apache fails to start with the following error:

    [core:emerg] [pid 90804] (28)No space left on device: AH00023: Couldn't create the proxy-balancer-shm mutex
    [proxy_balancer:emerg] [pid 90804] (28)No space left on device: AH01180: mutex creation of proxy-balancer-shm : myApacheServer failed


  • Red Hat Enterprise Linux (RHEL)
  • Red Hat Software Collections (RHSCL)
  • Red Hat JBoss Core Services (JBCS)
  • Apache Web Server (httpd)

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