Getting this output on your RHEL/CentOS virtual machine? Clocksource tsc unstable (delta = 000000000 ns). Enable clocksource failover by adding clocksource_failover kernel parameter. First find out the available clock sources : cat /sys/devices/system/clocksource/clocksource0/available_clocksource You will likely get the following results : kvm-clock tsc acpi_pm You are currently using “tsc” as per the initial output error, try… Read More »
I recently faced the following issue with VMware ESXi vSphere 5.5 hypervisor, trying to connect a USB device to a virtual machine. The host server was actually able to see the USB device : lsusb Bus 02 Device 04: ID 1058:0748 Western Digital Technologies, Inc. Bus 02 Device 03: ID 09eb:0131 IM Networks, Inc. Bus… Read More »
I recently observed this strange behavior from a Dell PowerEdge 2950 with PERC 6/i RAID controller. – One drive member from a RAID-5 array was failed – I pulled out the defective drive and pop in a brand new drive – Strangely, it did not started to sync and after a few moment, the drive… Read More »
If after a power outage or ESX hypervisor shutdown your iSCSI datastores are missing, it might be caused by a lock on the LUN on your host machine. You may find this in your vmkernel logs : /var/log/vmkernel.log 2014-02-19T04:19:11.927Z cpu3:33477)NMP: nmp_ThrottleLogForDevice:2321: Cmd 0x88 (0x412e80814440, 0) to dev “t10.FreeBSD_iSCSI_Disk______74867ae04094000_________________” on path “vmhba37:C0:T1:L0” Failed: H:0x2 D:0x0 P:0x0 Possible… Read More »
Here is how to configure DHCP forwarding across VLans on JunOS Juniper devices. set forwarding-options helpers bootp server <DHCP_SERVER_IP> set forwarding-options helpers bootp interface vlan.<VLAN_ID> Example : Assuming your DHCP server IP is “192.168.1.1” and the VLans you want DHCP forwarding enabled are “1” and “2” : set forwarding-options helpers bootp server 192.168.1.1 set forwarding-options… Read More »
Here is a quick reminder about the default username and password for Dell DRAC out-band server management : Username : root Password : calvin
UUIDs (Universal Unique Identifier) for network interface card can be generated using the following command : uuidgen <DEVICE> Example : uuidgen eth0 Then you can add it to your NIC config file (assuming your interface is eth0) : /etc/sysconfig/network-scripts/ifcfg-eth0 Add/modify the following : UUID=<uuid>
Did your Qmail server failed to receive a message including an attachment and showing this output in the SMTP logs? policy_check: remote sender@domain.tld -> local recipient@domain.tld (UNAUTHENTICATED SENDER) policy_check: policy allows transmission qmail-smtpd: qq soft reject (mail server temporarily rejected message (#4.3.0)): MAILFROM:<sender@domain.tld> RCPTTO:recipient@domain.tld tcpserver: end 0000 status 000 In this particular case, the version… Read More »
It’s possible to tell the kernel of your Xen guest VM to synchronize or not the clock with the physical host machine. There are numerous reason why you would or not to use this feature (such as your guest VM is behind or forward the clock over time). To find out the current setting, simply… Read More »
VMware ESXi management IP/vSphere connectivity might become suddenly unavailable over the time or after replacing the network interface card. This can be easily resolved by removing the vmnic port groupe for the management network and add it back again to the vSwitch. You will need direct console access to the ESX shell to perform these… Read More »