Configuring the base Linux system

This suggested disk layout usage is not required. It is a starting point solely because it is simple and it isolates emulated z Systems volumes from the normal Linux files. This isolation is useful if you reinstall Linux (without disturbing your emulated volumes) and it might have minor performance benefits because it tends to reduce fragmentation in the disk space that is used for large emulated volumes.

(3 GB x (number of volumes)) + (2 x (memory in your z/OS machine))

These examples assume that you are running z Systems Development and Test Environment under the user ID of ibmsys1.

Most of the z Systems Development and Test Environment related files that are mentioned in the customization scenario are stored within the ibmsys1 home directory. The scripts are in /home/ibmsys1/z, and the virtual 3390 volumes are stored in /home/ibmsys1/z1090/disks. The directory structure home/ibmsys1/z1090/disks was used because that directory structure complies with the structure created when you start the z Systems Development and Test Environment. The hardware clock was set to use Coordinated Universal Time (UTC) because that is required by the USB hardware device. The Linux user ID that was used is ibmsys1.

Set your hardware clock to UTC time to avoid problems when Daylight Saving Time starts and stops. The USB Hardware Device is sensitive to the hardware clock time and does not operate if the time appears to move backward. If the machine is shared with another operating system that expects local time (instead of UTC time), you might experience a one-hour non-operational time when you shift from Daylight Saving Time to standard time.

You must manage whatever firewall and other security functions that you install with your Linux. Initially disabling any firewall when first working with zPDT simplifies configuration and operation. After you are familiar with zPDT operation, you can reestablish the firewall functions. If you have external TCP/IP connections (for example, local 3270 connections, OSA connections, product license server or license manager connections, or CTC connections) you must provide appropriate port holes in any firewall you use.

Paragraph 13.15, “TCP/UDP ports” in the zPDT Guide and Reference, describes the ports that are used for normal zPDT operations. Port 1947 is also used by the license manager, and must be allowed through the firewall. If your firewall is based on iptables (as is common for most current Linux releases), commands such as those shown in the following example might be used. This example is for setting a rule to allow any emulated local 3270 session traffic through the firewall, and then displaying the rules for the filter table afterward

$ su (switch to root)
# iptables -I INPUT -p tcp --dport 3270 -j ACCEPT
# iptables -L -n 
# exit (leave root)

These commands would need to be entered from a root user ID each time the server Linux system is started, and you want to pursue some form of automation for entering these commands. Depending on how you connect z/OS to the external network, you might also need to provide appropriate port holes in your firewall to allow traffic to access z/OS ports, or you might need to use Network Address Translation functions in your firewall for this traffic.

The customizations described in this Guide eliminate the need to modify your firewall for z/OS ports. For more information, see Setting up TCP/IP.