Tools overview
Different tools can be used for obtaining dumps for instances of Red Hat® Enterprise Linux® 8.5 running on on IBM Z® (Z) or IBM® LinuxONE (LinuxONE) servers.
As of IBM z13®, simultaneous multithreading is available for Linux in LPAR mode. Red Hat Enterprise Linux as of version 7.2 includes dump tools that can create dumps for both Linux instances with and without SMT enablement.
Dump tools from earlier versions of Red Hat Enterprise Linux are restricted to Linux instances without SMT enablement. Do not use dump disks that were prepared with stand-alone dump tools of earlier versions to create dumps of SMT-enabled Linux instances.
You can use the dump analysis tool crash to analyze a dump. Depending on your support contract, you might also want to send a dump to IBM support to be analyzed.
Table 1 summarizes the available dump tools:
| Dump aspect | kdump | DASD | Multi- volume DASD | SCSI | Tape | virsh dump | VMDUMP |
|---|---|---|---|---|---|---|---|
| Environment | KVM, z/VM®, and LPAR | z/VM and LPAR | z/VM and LPAR | z/VM and LPAR | z/VM and LPAR | KVM only (see note 4) | z/VM only |
| System size (see note 1) | Large | Small | Large | Large | Large | Large | Small |
| Speed | Fast | Fast | Fast | Fast | Slow | Fast | Slow |
| Medium | Any available medium | ECKD or FBA (see note 2) DASD | ECKD DASD | SCSI disk partition | Tape cartridges | Any available medium | z/VM reader |
| Compression possible | While writing | No | No | No | Yes (see note 1) | No | No |
| Dump filtering possible | While writing | When copying | When copying | When copying | When copying | When copying | When copying |
| Disruptive (see note 3) | Yes | Yes | Yes | Yes | Yes | Optional | No |
| Stand-alone | No | Yes | Yes | Yes | Yes | No | No |
- For dump system sizes, see also Maximum dump size by tool.
- SCSI disks can be emulated as FBA disks. This dump method can, therefore, be used for SCSI-only z/VM installations.
- In this context, disruptive means that the dump process kills a running operating system.
- You cannot use virsh dump to create a dump of a KVM guests in IBM Secure Execution mode.
Note on device nodes
In all examples, the traditional device nodes for DASD, tape, and SCSI devices are used. You can also use the device nodes that udev creates for you.