zipl environment - Variables for the kernel command line

6.10 LPAR mode z/VM guest KVM guest

zipl prepares an IPL device by installing boot data and a boot record that points to this data. The boot data includes kernel parameter lines.

The straightforward way to change any installed parameter line is to rerun zipl. However, you can avoid rerunning zipl. For this, define variable parts of your parameter line (such as numerical values of timeouts) with zipl environment variables and define those variables in a special boot data component, called a zipl environment block.

Once the zipl environment block is installed along with other zipl components, you don't need to rerun zipl to change the variable parts: All you have to do is redefine the variables and update only the installed environment block.

Hence, a zipl environment block contains specifications for resolving variables in the kernel command line. These specifications apply to all menu entries that you create and install with zipl.

The installed zipl environment block is interpreted at boot time. zipl creates the zipl environment block from a zipl environment file on the administrative Linux instance, from which you run zipl. See Creating variables for the kernel command line.

Using the zipl environment feature, you can:
Figure 1 shows the relationship between the zipl environment file and zipl environment block.
Figure 1. zipl environment block and file
This figure is described in the text that precedes it

Use the zipl-editenv command to modify the zipl environment block directly.