2.3. Red Hat Enterprise Linux Operating System Requirements

Directory Server is supported on two versions of Red Hat Enterprise Linux:

Red Hat Enterprise Linux 4 on x86 and x86_64 platforms
Red Hat Enterprise Linux 5 on x86 and x86_64 platforms

NOTE

Red Hat Directory Server is also supported running on a virtual guest on a Red Hat Enterprise Linux virtual server.

Both Red Hat Enterprise Linux versions on both 32-bit and 64-bit platforms have the same system requirements, as listed in Table 2.2, “Red Hat Enterprise Linux Operating System and Hardware Requirements”. The patches required are listed in Section 2.3.1, “Red Hat Enterprise Linux Patches”, and the recommended system configuration changes are described in Section 2.3.2, “Red Hat Enterprise Linux System Configuration”.

Table 2.2. Red Hat Enterprise Linux Operating System and Hardware Requirements

Criteria	Requirements
Operating System	Red Hat Enterprise Linux 4 or 5 with the latest patches and upgrades
CPU Type	Pentium 4 or higher; 2 GHz or higher
Memory/RAM	1 GB minimum, up to the system limit
Hard Disk	4 GB minimum
Other	To run the Directory Server using port numbers less than 1024, such as the default port 389, you must setup and start the Directory Server as `root`, but it is not necessary to run the Directory Server as `root`.

2.3.1. Red Hat Enterprise Linux Patches

The default kernel and glibc versions for Red Hat Enterprise Linux 4 and 5 are the only required versions for the Red Hat Directory Server host machine. If the machine has a single CPU, the kernel must be presented in the form kernel-x.x.x.x. If the machine has multiple CPUs, the kernel must be presented the form kernel-smp-x.x.x.x. To determine the components running on the machine, run rpm -qa.

Run the dsktune utility to see if you need to install any other patches. dsktune helps verify whether the appropriate patches are installed on the system and provides useful information for tuning your kernel parameters for best performance. For information on dsktune, see Section 2.2, “Using dsktune”.

Table 2.3. System Versions

Criteria

Requirements

Operating System

Red Hat Enterprise Linux 4 Server (x86 and x86_64)

Red Hat Enterprise Linux 5 Server (x86 and x86_64)

Required Filesystem

ext3

2.3.2. Red Hat Enterprise Linux System Configuration

After verifying the system's kernel and glibc configuration and installing any required modules and patches, fine-tune the Red Hat Enterprise Linux system to work with Directory Server. For the best performance, configure the host server before configuring the Directory Server instance by running the setup-ds-admin.pl script.

2.3.2.1. Perl Prerequisites

For Red Hat Enterprise Linux systems, use the Perl version that is installed with the operating system in /usr/bin/perl for both 32-bit and 64-bit versions of Red Hat Directory Server.

2.3.2.2. File Descriptors

Editing the number of file descriptors on the Linux system can help Directory Server access files more efficiently. Editing the maximum number of file descriptors the kernel can allocate can also improve file access speeds.

First, check the current limit for file descriptors:
```
cat /proc/sys/fs/file-max
```
If the setting is lower than 64000, edit the /etc/sysctl.conf file, and reset the fs.file-max parameter:
```
fs.file-max = 64000
```
Then increase the maximum number of open files on the system by editing the /etc/security/limits.conf configuration file. Add the following entry:
```
*        -        nofile        8192
```

Edit the /etc/pam.d/system-auth, and add this entry:

session required /lib/security/$ISA/pam_limits.so

Reboot the Linux machine to apply the changes.

2.3.2.3. DNS Requirements

It is very important that DNS and reverse DNS be working correctly on the host machine, especially if you are using TLS/SSL or Kerberos with Directory Server.

Configure the DNS resolver and the NIS domain name by the modifying the /etc/resolv.conf, /etc/nsswitch.conf, and /etc/netconfig files, and set the DNS resolver for name resolution.

Edit the /etc/defaultdomain file to include the NIS domain name. This ensures that the fully-qualified host and domain names used for the Directory Server resolve to a valid IP address and that that IP address resolves back to the correct hostname.

Reboot the Red Hat Enterprise Linux machine to apply these changes.