I am using Apache 2.4.6 with CentOS 7, we have number of VirtualHost (around 500+) running on this server including SSL/Non-SSL. Most of virtualhost has load balanced nodes using mod_proxy_balancer.

So Now I am started facing the problem when configure new website/VirtualHost. When I add new VirtualHost and restart apache I getting below error in log.

[auth_digest:notice] [pid 64800] AH01757: generating secret for digest authentication ...
[lbmethod_heartbeat:notice] [pid 64800] AH02282: No slotmem from mod_heartmonitor
[core:emerg] [pid 64800] (28)No space left on device: AH00023: Couldn't create the proxy-balancer-shm mutex
[proxy_balancer:emerg] [pid 64800] (28)No space left on device: AH01180: mutex creation of proxy-balancer-shm : pcf1e59f3_x_xxxxxxx failed
[:emerg] [pid 64800] AH00020: Configuration Failed, exiting

I've searched on web for this issue before posting here, I got few solutions like killing semaphores, increasing max open files/max processes limit but none of those worked in my case.

Also I think my server configuration is strong enough to handle huge number of VirtualHost, it is as below. Centos 7 64 bit dedicated box, with 512G RAM and 24 core/48 threads Processor.

Please respond me if anyone has resolved this issue, Thanks

  • Please list how much free disk space you have there. – JayMcTee Aug 1 '17 at 9:25

I assume you've already made sure you have enough space on the disk Apache is running on.

Other than killing stuck semaphores, have you tried increasing the actual number of available semaphores kernel-side under kernel.sem and kernel.msgmni? I found this article which goes more in depth about it.

  • Thanks @MarkkulT, I managed it by modifying the kernel.sem limits, but I wondering if it is safe for production server and what would be the recommended parameters as per hardware resources. – Vaibhav Panmand Aug 1 '17 at 8:40

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