Working with Server Logs

The CloudStack Management Server logs all web site, middle tier, and database activities for diagnostics purposes in /var/log/cloudstack/management/. The CloudStack logs a variety of error messages. We recommend this command to find the problematic output in the Management Server log:.


When copying and pasting a command, be sure the command has pasted as a single line before executing. Some document viewers may introduce unwanted line breaks in copied text.

grep -i -E 'exception|unable|fail|invalid|leak|warn|error' /var/log/cloudstack/management/management-server.log

The CloudStack processes requests with a Job ID. If you find an error in the logs and you are interested in debugging the issue you can grep for this job ID in the management server log. For example, suppose that you find the following ERROR message:

2010-10-04 13:49:32,595 ERROR [cloud.vm.UserVmManagerImpl] (Job-Executor-11:job-1076) Unable to find any host for [User|i-8-42-VM-untagged]

Note that the job ID is 1076. You can track back the events relating to job 1076 with the following grep:

grep "job-1076)" management-server.log

The CloudStack Agent Server logs its activities in /var/log/cloudstack/agent/.

Data Loss on Exported Primary Storage


Loss of existing data on primary storage which has been exposed as a Linux NFS server export on an iSCSI volume.


It is possible that a client from outside the intended pool has mounted the storage. When this occurs, the LVM is wiped and all data in the volume is lost


When setting up LUN exports, restrict the range of IP addresses that are allowed access by specifying a subnet mask. For example:

echo “/export,async,no_root_squash,no_subtree_check)” > /etc/exports

Adjust the above command to suit your deployment needs.

More Information

See the export procedure in the “Secondary Storage” section of the CloudStack Installation Guide

Recovering a Lost Virtual Router


A virtual router is running, but the host is disconnected. A virtual router no longer functions as expected.


The Virtual router is lost or down.


If you are sure that a virtual router is down forever, or no longer functions as expected, destroy it. You must create one afresh while keeping the backup router up and running (it is assumed this is in a redundant router setup):

  • Force stop the router. Use the stopRouter API with forced=true parameter to do so.
  • Before you continue with destroying this router, ensure that the backup router is running. Otherwise the network connection will be lost.
  • Destroy the router by using the destroyRouter API.

Recreate the missing router by using the restartNetwork API with cleanup=false parameter. For more information about redundant router setup, see Creating a New Network Offering.

For more information about the API syntax, see the API Reference at

Maintenance mode not working on vCenter


Host was placed in maintenance mode, but still appears live in vCenter.


The CloudStack administrator UI was used to place the host in scheduled maintenance mode. This mode is separate from vCenter’s maintenance mode.


Use vCenter to place the host in maintenance mode.

Unable to deploy VMs from uploaded vSphere template


When attempting to create a VM, the VM will not deploy.


If the template was created by uploading an OVA file that was created using vSphere Client, it is possible the OVA contained an ISO image. If it does, the deployment of VMs from the template will fail.


Remove the ISO and re-upload the template.

Unable to power on virtual machine on VMware


Virtual machine does not power on. You might see errors like:

  • Unable to open Swap File
  • Unable to access a file since it is locked
  • Unable to access Virtual machine configuration


A known issue on VMware machines. ESX hosts lock certain critical virtual machine files and file systems to prevent concurrent changes. Sometimes the files are not unlocked when the virtual machine is powered off. When a virtual machine attempts to power on, it can not access these critical files, and the virtual machine is unable to power on.


See the following:

VMware Knowledge Base Article

Load balancer rules fail after changing network offering


After changing the network offering on a network, load balancer rules stop working.


Load balancing rules were created while using a network service offering that includes an external load balancer device such as NetScaler, and later the network service offering changed to one that uses the CloudStack virtual router.


Create a firewall rule on the virtual router for each of your existing load balancing rules so that they continue to function.

Troubleshooting Internet Traffic

Below are a few troubleshooting steps to check whats going wrong with your network…

Trouble Shooting Steps

  1. The switches have to be configured correctly to pass VLAN traffic. You can verify if VLAN traffic is working by bringing up a tagged interface on the hosts and pinging between them as below…

    On host1 (kvm1)

    kvm1 ~$ vconfig add eth0 64
    kvm1 ~$ ifconfig eth0.64 netmask up
    kvm1 ~$ ping

    On host2 (kvm2)

    kvm2 ~$ vconfig add eth0 64
    kvm2 ~$ ifconfig eth0.64 netmask up
    kvm2 ~$ ping

    If the pings dont work, run tcpdump(8) all over the place to check who is gobbling up the packets. Ultimately, if the switches are not configured correctly, CloudStack networking wont work so fix the physical networking issues before you proceed to the next steps

  2. Ensure Traffic Labels are set for the Zone.

    Traffic labels need to be set for all hypervisors including XenServer, KVM and VMware types. You can configure traffic labels when you creating a new zone from the Add Zone Wizard.


    On an existing zone, you can modify the traffic labels by going to Infrastructure, Zones, Physical Network tab.


    List labels using CloudMonkey

    acs-manager ~$ cloudmonkey list traffictypes physicalnetworkid=41cb7ff6-8eb2-4630-b577-1da25e0e1145
    count = 4
    id = cd0915fe-a660-4a82-9df7-34aebf90003e
    kvmnetworklabel = cloudbr0
    physicalnetworkid = 41cb7ff6-8eb2-4630-b577-1da25e0e1145
    traffictype = Guest
    xennetworklabel = MGMT
    id = f5524b8f-6605-41e4-a982-81a356b2a196
    kvmnetworklabel = cloudbr0
    physicalnetworkid = 41cb7ff6-8eb2-4630-b577-1da25e0e1145
    traffictype = Management
    xennetworklabel = MGMT
    id = 266bad0e-7b68-4242-b3ad-f59739346cfd
    kvmnetworklabel = cloudbr0
    physicalnetworkid = 41cb7ff6-8eb2-4630-b577-1da25e0e1145
    traffictype = Public
    xennetworklabel = MGMT
    id = a2baad4f-7ce7-45a8-9caf-a0b9240adf04
    kvmnetworklabel = cloudbr0
    physicalnetworkid = 41cb7ff6-8eb2-4630-b577-1da25e0e1145
    traffictype = Storage
    xennetworklabel = MGMT
  3. KVM traffic labels require to be named as “cloudbr0”, “cloudbr2”, “cloudbrN” etc and the corresponding bridge must exist on the KVM hosts. If you create labels/bridges with any other names, CloudStack (atleast earlier versions did) seems to ignore them. CloudStack does not create the physical bridges on the KVM hosts, you need to create them before before adding the host to Cloudstack.

    kvm1 ~$ ifconfig cloudbr0
    cloudbr0  Link encap:Ethernet  HWaddr 00:0C:29:EF:7D:78
       inet addr:  Bcast:  Mask:
       inet6 addr: fe80::20c:29ff:feef:7d78/64 Scope:Link
       RX packets:92435 errors:0 dropped:0 overruns:0 frame:0
       TX packets:50596 errors:0 dropped:0 overruns:0 carrier:0
       collisions:0 txqueuelen:0
       RX bytes:94985932 (90.5 MiB)  TX bytes:61635793 (58.7 MiB)
  4. The Virtual Router, SSVM, CPVM public interface would be bridged to a physical interface on the host. In the example below, cloudbr0 is the public interface and CloudStack has correctly created the virtual interfaces bridge. This virtual interface to physical interface mapping is done automatically by CloudStack using the traffic label settings for the Zone. If you have provided correct settings and still dont have a working working Internet, check the switching layer before you debug any further. You can verify traffic using tcpdump on the virtual, physical and bridge interfaces.

    kvm-host1 ~$ brctl show
    bridge name  bridge id           STP enabled interfaces
    breth0-64    8000.000c29ef7d78   no          eth0.64
    cloud0       8000.fe00a9fe0219   no          vnet0
    cloudbr0     8000.000c29ef7d78   no          eth0
    virbr0       8000.5254008e321a   yes         virbr0-nic
    xenserver1 ~$ brctl show
    bridge name  bridge id           STP enabled interfaces
    xapi0    0000.e2b76d0a1149       no          vif1.0
    xenbr0   0000.000c299b54dc       no          eth0
  5. Pre-create labels on the XenServer Hosts. Similar to KVM bridge setup, traffic labels must also be pre-created on the XenServer hosts before adding them to CloudStack.

    xenserver1 ~$ xe network-list
    uuid ( RO)                : aaa-bbb-ccc-ddd
              name-label ( RW): MGMT
        name-description ( RW):
                  bridge ( RO): xenbr0
  6. The Internet would be accessible from both the SSVM and CPVM instances by default. Their public IPs will also be directly pingable from the Internet. Please note that these test would work only if your switches and traffic labels are configured correctly for your environment. If your SSVM/CPVM cant reach the Internet, its very unlikely that the Virtual Router (VR) can also the reach the Internet suggesting that its either a switching issue or incorrectly assigned traffic labels. Fix the SSVM/CPVM issues before you debug VR issues.

    root@s-1-VM:~# ping -c 3
    PING ( 56 data bytes
    64 bytes from icmp_seq=0 ttl=55 time=26.932 ms
    64 bytes from icmp_seq=1 ttl=55 time=29.156 ms
    64 bytes from icmp_seq=2 ttl=55 time=25.000 ms
    --- ping statistics ---
    3 packets transmitted, 3 packets received, 0% packet loss
    round-trip min/avg/max/stddev = 25.000/27.029/29.156/1.698 ms
    root@v-2-VM:~# ping -c 3
    PING ( 56 data bytes
    64 bytes from icmp_seq=0 ttl=55 time=32.125 ms
    64 bytes from icmp_seq=1 ttl=55 time=26.324 ms
    64 bytes from icmp_seq=2 ttl=55 time=37.001 ms
    --- ping statistics ---
    3 packets transmitted, 3 packets received, 0% packet loss
    round-trip min/avg/max/stddev = 26.324/31.817/37.001/4.364 ms
  7. The Virtual Router (VR) should also be able to reach the Internet without having any Egress rules. The Egress rules only control forwarded traffic and not traffic that originates on the VR itself.

    root@r-4-VM:~# ping -c 3
    PING ( 56 data bytes
    64 bytes from icmp_seq=0 ttl=55 time=28.098 ms
    64 bytes from icmp_seq=1 ttl=55 time=34.785 ms
    64 bytes from icmp_seq=2 ttl=55 time=69.179 ms
    --- ping statistics ---
    3 packets transmitted, 3 packets received, 0% packet loss
    round-trip min/avg/max/stddev = 28.098/44.021/69.179/17.998 ms
  8. However, the Virtual Router’s (VR) Source NAT Public IP address WONT be reachable until appropriate Ingress rules are in place. You can add Ingress rules under Network, Guest Network, IP Address, Firewall setting page.

  9. The VM Instances by default wont be able to access the Internet. Add Egress rules to permit traffic.

  10. Some users have reported that flushing IPTables rules (or changing routes) on the SSVM, CPVM or the Virtual Router makes the Internet work. This is not expected behaviour and suggests that your networking settings are incorrect. No IPtables/route changes are required on the SSVM, CPVM or the VR. Go back and double check all your settings.

In a vast majority of the cases, the problem has turned out to be at the switching layer where the L3 switches were configured incorrectly.

This section was contibuted by Shanker Balan and was originally published on Shapeblue’s blog