Article ID: 10007, created on Mar 2, 2011, last review on Jun 17, 2016

  • Applies to:
  • Virtuozzo
  • Virtuozzo containers for Linux
  • Virtuozzo hypervisor


Stop the virtual machine and add a COM port as shown in the picture below:




When starting the VM, enter the boot loader menu (by typing "E" when the GRUB window appears):


Select the line with the kernel options and hit "E" once again:


Or via command line:

# prlctl set VM_NAME --device-add serial --output /var/parallels/VM_NAME.pvm/serial2.txt

Append the string with the debug console=<ttySN>,115200 console=tty options and hit Enter.

NOTE: <ttySN> represents a COM port name with its number. If you have the only serial port attached to the virtual machine, then it would be ttyS0; if there are several, then you should be able to find it by issuing this command:

# prlctl list –i VMNAME | grep serial

For example:

[root@hostserver ~]# prlctl list -i 'CentOS Linux' | grep serial    
serial0 (+) socket='/tmp/com_1'
serial1 (+) output='/vz/vmprivate/CentOS Linux.pvm/serial2.txt'

So, in this example, it would be ttyS1:


The resulting window should look like this:


Now hit "b" to boot the selected kernel, and in the meantime, check the output file that was specified from the host server:

[root@hostserver ~]# tail –f '/vz/vmprivate/CentOS 5.5 x64 Serial Console.pvm/serial2.txt'
Linux version 2.6.18-194.el5 ( (gcc version 4.1.2 20080704 (Red Ha
t 4.1.2-48)) #1 SMP Fri Apr 2 14:58:14 EDT 2010
Command line: ro root=LABEL=/1 debug console=ttyS1,115200 console=tty
BIOS-provided physical RAM map:
BIOS-e820: 0000000000010000 - 000000000009fc00 (usable)
BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000dc000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 000000007fff0000 (usable)
BIOS-e820: 000000007fff0000 - 000000007ffff000 (ACPI data)
BIOS-e820: 000000007ffff000 - 0000000080000000 (ACPI NVS)
BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
BIOS-e820: 00000000ffc00000 - 0000000100000000 (reserved)
DMI 2.3 present.
ACPI: RSDP (v002 PRLS                                  ) @ 0x00000000000e8000
ACPI: XSDT (v001 PRLS   PRLS_OEM 0x00000001 INTL 0x20051216) @ 0x000000007fff0040
ACPI: FADT (v003 PRLS   PRLS_OEM 0x00000001 INTL 0x20051216) @ 0x000000007fff0100
ACPI: MADT (v001 PRLS   PRLS_OEM 0x00000001 INTL 0x20051216) @ 0x000000007fff0240
ACPI: DSDT (v002 PRLS   PRLSACPI 0x00001001 INTL 0x20051216) @ 0x0000000000000000
No NUMA configuration found
Faking a node at 0000000000000000-000000007fff0000
Bootmem setup node 0 0000000000000000-000000007fff0000
Memory for crash kernel (0x0 to 0x0) notwithin permissible range
disabling kdump
On node 0 totalpages: 515693

Thus, when the kernel panic message appears, you will have the exact text output that can be used for searching in RedHat bugzilla and forums.

When submitting a request to Parallels Technical Support, please have the output file attached.

Additional Information

Also see this article about configuring the serial console output for MacOS-based VMs:

  • 113113 How to troubleshoot kernel panic in MacOS-based virtual machine

Search Words

console log

kernel panic

unable to handle kernel null pointer

serial console

virtuozzo problem read-only

com port

a26b38f94253cdfbf1028d72cf3a498b 2897d76d56d2010f4e3a28f864d69223 0dd5b9380c7d4884d77587f3eb0fa8ef e8e50b42231236b82df27684e7ec0beb d02f9caf3e11b191a38179103495106f

Email subscription for changes to this article
Save as PDF