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.
- Linux must be compiled to support rebooting from an alternative source. This feature is built into the kernel by default.
- The IBM Z® hardware must have SCSI IPL support for re-IPL from SCSI devices.
Use the chreipl tool to configure the re-IPL device.
Alternatively, you can use a sysfs interface. In sysfs, 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.
- eckd
- For ECKD DASDs with the secure-boot enabled format of the boot data. In contrast to the ccw ipl type, list-directed IPL is used.
- 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.