Rebooting from an alternative source
When you reboot Linux, the system conventionally boots from the last used location. However, you can configure an alternative device to be used for re-IPL instead of the last used IPL device.
When the system is re-IPLed, the alternative device is used to boot the kernel.
To configure the re-IPL device, use the chreipl tool.
Alternatively, you can use a sysfs interface. The virtual configuration files are located under /sys/firmware/reipl. To configure, write strings into the configuration files. The following re-IPL types can be set with the /sys/firmware/reipl/reipl_type attribute:
- ccw
- For ccw devices such as DASDs that are attached through ESCON or FICON®, and for virtio block devices on KVM guests.
- fcp
- For FCP SCSI devices. For information about boot devices, see Table 1.
- nvme
- For PCIe-attached NVMe devices.
- nss
- For Named Saved Systems (z/VM® only)
For each supported re-IPL type a sysfs directory is created under /sys/firmware/reipl that contains the configuration attributes for the device. The directory name is the same as the name of the re-IPL type.
When Linux is booted, the re-IPL attributes are set by default to the values of the boot device, which can be found under /sys/firmware/ipl.
Automatic path failover for re-IPL from an FC-attached SCSI disk
The chreipl-fcp-mpath tool set helps you to use multipath information for re-IPL path failover on a running Linux instance. When the configured re-IPL path becomes unavailable it automatically changes the configured re-IPL path to a different operational path to the same volume.
To use the tool set, install the s390utils-chreipl-fcp-mpath sub-package from s390-utils. Disable the feature by un-installing the sub-package. For more information, see the documentation installed with the sub-package: /usr/share/doc/s390utils-chreipl-fcp-mpath/README.md.