How to display Xen boot and runtime messages

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When a host system is booted with a Xen enabled kernel a series of diagnostic messages are output to the console. Subsequently during the course of operation additional messages are generated by the hypervisor and domain0. Both sets of messages may be of use when attempting to resolve problems with the virtualization environment.

The messages generated by the Xen daemon process may be viewed and using the xm dmesg command. In addition, the current message buffer may be cleared using the -c flag. For example to clear the message buffer:

xm dmesg -c

The following example shows the typical output from the xm dmesg command:

# xm dmesg
 __  __            _____  _   ___    ____ _____  _   _ _  _        _ ____  
 \ \/ /___ _ __   |___ / / | / _ \  | ___|___ / / | / | || |   ___| | ___| 
  \  // _ \ \047_ \    |_ \ | || | | |_|___ \ |_ \ | | | | || |_ / _ \ |___ \ 
  /  \  __/ | | |  ___) || || |_| |__|__) |__) || |_| |__   _|  __/ |___) |
 /_/\_\___|_| |_| |____(_)_(_)___/  |____/____(_)_(_)_|  |_|(_)___|_|____/ 
                                                                           
 http://www.cl.cam.ac.uk/netos/xen
 University of Cambridge Computer Laboratory

 Xen version 3.1.0-53.1.14.el5 ([email protected]) (gcc version 4.1.2 20070626 (Red Hat 4.1.2-14)) Tue Feb 19 07:15:12 EST 2008
 Latest ChangeSet: unavailable

(XEN) Command line: /xen.gz-2.6.18-53.1.14.el5
(XEN)  0000000000000000 - 000000000009f000 (usable)
(XEN)  000000000009f800 - 00000000000a0000 (reserved)
(XEN)  00000000000ca000 - 00000000000cc000 (reserved)
(XEN)  00000000000dc000 - 0000000000100000 (reserved)
(XEN)  0000000000100000 - 00000000346f0000 (usable)
(XEN)  00000000346f0000 - 00000000346ff000 (ACPI data)
(XEN)  00000000346ff000 - 0000000034700000 (ACPI NVS)
(XEN)  0000000034700000 - 0000000034800000 (usable)
(XEN)  00000000fec00000 - 00000000fec10000 (reserved)
(XEN)  00000000fee00000 - 00000000fee01000 (reserved)
(XEN)  00000000fffe0000 - 0000000100000000 (reserved)
(XEN) System RAM: 839MB (859708kB)
(XEN) Xen heap: 10MB (10244kB)
(XEN) Domain heap initialised: DMA width 32 bits
(XEN) PAE enabled, limit: 16 GB
(XEN) Processor #0 15:6 APIC version 17
(XEN) IOAPIC[0]: apic_id 1, version 17, address 0xfec00000, GSI 0-23
(XEN) Enabling APIC mode:  Flat.  Using 1 I/O APICs
(XEN) Using scheduler: SMP Credit Scheduler (credit)
(XEN) Detected 2993.833 MHz processor.
(XEN) CPU0: Intel(R) Pentium(R) D CPU 3.00GHz stepping 08
(XEN) Mapping cpu 0 to node 255
(XEN) Total of 1 processors activated.
(XEN) ENABLING IO-APIC IRQs
(XEN)  -> Using new ACK method
(XEN) Platform timer is 1.193MHz PIT
(XEN) Brought up 1 CPUs
(XEN) *** LOADING DOMAIN 0 ***
(XEN) elf_parse_binary: phdr: paddr=0xc0400000 memsz=0x25d640
(XEN) elf_parse_binary: phdr: paddr=0xc065e000 memsz=0x15a000
(XEN) elf_parse_binary: memory: 0xc0400000 -> 0xc07b8000
(XEN) elf_xen_parse_note: GUEST_OS = "linux"
(XEN) elf_xen_parse_note: GUEST_VERSION = "2.6"
(XEN) elf_xen_parse_note: XEN_VERSION = "xen-3.0"
(XEN) elf_xen_parse_note: VIRT_BASE = 0xc0000000
(XEN) elf_xen_parse_note: PADDR_OFFSET = 0xc0000000
(XEN) elf_xen_parse_note: ENTRY = 0xc0400000
(XEN) elf_xen_parse_note: HYPERCALL_PAGE = 0xc0401000
(XEN) elf_xen_parse_note: FEATURES = "writable_page_tables|writable_descriptor_tables|auto_translated_physmap|pae_pgdir_above_4gb|supervisor_mode_kernel"
(XEN) elf_xen_parse_note: PAE_MODE = "yes"
(XEN) elf_xen_parse_note: LOADER = "generic"
(XEN) elf_xen_addr_calc_check: addresses:
(XEN)     virt_base        = 0xc0000000
(XEN)     elf_paddr_offset = 0xc0000000
(XEN)     virt_offset      = 0x0
(XEN)     virt_kstart      = 0xc0400000
(XEN)     virt_kend        = 0xc07b8000
(XEN)     virt_entry       = 0xc0400000
(XEN)  Xen  kernel: 32-bit, PAE, lsb
(XEN)  Dom0 kernel: 32-bit, PAE, lsb, paddr 0xc0400000 -> 0xc07b8000
(XEN) PHYSICAL MEMORY ARRANGEMENT:
(XEN)  Dom0 alloc.:   0000000033000000->0000000034000000 (192948 pages to be allocated)
(XEN) VIRTUAL MEMORY ARRANGEMENT:
(XEN)  Loaded kernel: c0400000->c07b8000
(XEN)  Init. ramdisk: c07b8000->c0e6c600
(XEN)  Phys-Mach map: c0e6d000->c0f2d6d0
(XEN)  Start info:    c0f2e000->c0f2e46c
(XEN)  Page tables:   c0f2f000->c0f3c000
(XEN)  Boot stack:    c0f3c000->c0f3d000
(XEN)  TOTAL:         c0000000->c1000000
(XEN)  ENTRY ADDRESS: c0400000
(XEN) Dom0 has maximum 1 VCPUs
(XEN) elf_load_binary: phdr 0 at 0xc0400000 -> 0xc065d640
(XEN) elf_load_binary: phdr 1 at 0xc065e000 -> 0xc0702b64
(XEN) Initrd len 0x6b4600, start at 0xc07b8000
(XEN) Scrubbing Free RAM: done.
(XEN) Xen trace buffers: disabled
(XEN) Std. Loglevel: Errors and warnings
(XEN) Guest Loglevel: Nothing (Rate-limited: Errors and warnings)
(XEN) Xen is relinquishing VGA console.
(XEN) *** Serial input -> DOM0 (type \047CTRL-a\047 three times to switch input to Xen).
(XEN) mtrr: your processor doesn\047t support write-combining
(XEN) mtrr: your processor doesn\047t support write-combining