Host Machine Requirements

Host machines must meet a set of requirements for Pivotal GemFire.

Each machine that will run Pivotal GemFire must meet the following requirements:

A supported Java SE installation.
An adequate per-user limit on the number of file descriptors; for Unix/Linux, the recommended soft limit is 8192, and the hard limit is 81920.
An adequate per-user limit on the number of processes (nproc); for Unix/Linux, the recommended soft limit is 501408, with an unlimited hard limit.
TCP/IP.
A system clock set to the correct time and a time synchronization service such as Network Time Protocol (NTP). Correct time stamps permit the following activities:
- Logs that are useful for troubleshooting. Synchronized time stamps ensure that log messages from different hosts can be merged to reproduce an accurate chronological history of a distributed run.
- Aggregate product-level and application-level time statistics.
- Accurate monitoring of the GemFire system with scripts and other tools that read the system statistics and log files.
The host name and host files are properly configured for the machine. The host name and host file configuration can affect gfsh and Pulse functionality. For Unix/Linux hosts, see the system man pages for more information on setting the host name and hosts.
Many default Linux installations use SYN cookies to protect the system against malicious attacks that flood TCP SYN packets. The use of SYN cookies dramatically reduces network bandwidth, and can be triggered by a running GemFire distributed system.
To disable SYN cookies permanently:
1. Edit the /etc/sysctl.conf file to include the following line:
```
net.ipv4.tcp_syncookies = 0
```
  Setting this value to zero disables SYN cookies.
2. Reload sysctl.conf:
```
sysctl -p
```