You see a message “Unable to fork: Cannot allocate memory” while logging to a VPS from the host server. The reason is the VPS is running out of resources especially RAM. To temporary solve the issue, you may restart the VPS by executing vzctl restart VEID OR increase RAM for the VPS by increasing privvmpages [...]

This parameter defines how many simultaneous request can be served. Any connection request from browsers that come in after that will be queued.

The MaxClients directive sets the limit on the number of simultaneous requests that can be supported. No more than this number of child server processes will be created. To configure more than 256 clients, you must edit the HARD_SERVER_LIMIT entry in httpd.h and recompile. In our case we want this variable to be as small [...]

Q. How do I identify Linux server ECC memory modules from a shell prompt? A. You need to count the chips on the module. If memory module has 9 chips per sides, it is ECC memory (EDAC protected memory). It may or may not be registered. If the memory module has 8 chips per side, [...]