Difference between revisions of "Troubleshooting"

Revision as of 12:20, 28 November 2016

Introduction

This side is a miscellany of troubleshooting Technics.

Debugging Installation

Can be used if you can't boot your PVE Host.

See Debugging_Installation

Enable kernel dumb

If you have a kernel panic it can be very usful to have a kernel dump to analyse the problem.

See Enable_Core_Dump_systemd

Debug LXC

When a Container fail to start.

See Linux_Container paragraph "Obtaining Debugging Logs".

Switch novnc KVM console

I can't switch virtual consoles in Linux KVM guests with alt-F1, alt-F2... VNC viewer does not pass some key combinations or they may be intercepted by your operating system.

To send custom key combinations to the guest, go to "Monitor" in Virtual Machine Configuration for a given guest and use "sendkey" command.

For example, to switch to the third console (tty3) you would use:

sendkey alt-f3

How can I send sysrq to Linux KVM guests?

Similarly to the above, go to "Monitor" in Virtual Machine Configuration for a given guest and use "sendkey" command.

For example, to issue "Emergency Sync", you would use:

sendkey alt-sysrq-s

In the VNC viewer for the given guest you should see:

SysRq : Emergency Sync

You should also see this entry if you run "dmesg" on this guest.

See also http://en.wikipedia.org/wiki/Magic_SysRq_key for a full reference of possible combinations.

How can I access Linux guests through a serial terminal

See Serial Terminal

How can I assign a physical disk to a VM?

You don't have to do anything at host level (i.e. not add to fstab or anything), just set is as available directly to the KVM guest:

qm set <vmid> -ide# /dev/sdb

Or:

qm set <vmid> -ide# /dev/disk/by-id/[your disk ID]

...since having the drive letter change (should you add a drive) might have unintended consequences.

Also see /etc/qemu-server/<vmid>.conf if you want to add it editing the conf file by hand (i.e. adding ide1: /dev/sdb2). After that you can run the VM as usual, and you will have the new storage device available inside it. Beware that you can't assign it to more than one running VM if the filesystem is not designed for such scenario.

How can I assign a physical disk to a CT?

See http://wiki.openvz.org/Bind_mounts

"error: out of partition" after a fresh install

The error message below may happens when you had two or more harddrives connected during the installation. Try to disconnect all but one disk.

error: out of partition.
grub rescue>

NFS Client Mount Error: "mount.nfs: No such device"

By default NFS cannot be mounted in VZ containers. See this page to set-it-up: OpenVZ: NFS See also this page to make an host's directory visible to a container: OpenVZ: Bind mounts

Cluster & Multicast issues

See Troubleshooting multicast, quorum and cluster issues.