Author Archives: Kaven Gagnon

About Kaven Gagnon

System & Network Architect

VMware : iSCSI LUN datastore no longer visible after outage

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 »

JunOS : Setting up DHCP forwarding

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 »

Dell : Default username and password for DRAC

Here is a quick reminder about the default username and password for Dell DRAC out-band server management : Username : root Password : calvin

Linux : How to generate UUID for network interface on RHEL/CentOS

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>

Linux : qmail-smtpd: qq soft reject (mail server temporarily rejected message (#4.3.0))

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 »

Linux : Guest VM time sync with Xen host

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 host no longer available after replacing the network interface

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 »

Linux : Force network interface speed and duplex with EthTool

Here is a quick how to force your network interface speed and duplex on RHEL/CentOS Linux. Make sure you have the network tools installed : yum install ethtool net-tools To apply the configuration without having to restart the network service or reboot your system, simply do this command with your settings : ethtool -s <INTERFACE>… Read More »

Linux : PHP Unable to load dynamic library ‘/usr/lib64/php/modules/module.so

Having this error on your RHEL/CentOS 6 Web server or issuing “php -v” command? PHP Warning: PHP Startup: Unable to load dynamic library ‘/usr/lib64/php/modules/module.so’ – /usr/lib64/php/modules/module.so: cannot open shared object file: No such file or directory in Unknown on line 0 Then you probably have “php-mcrypt” module installed. Apparently, the “mcrypt.ini” file do not have… Read More »

Linux : Unable to connect to xend: No such file or directory. Is xend running?

Ending up with this kind of error booting a guest machine on your Xen hypervisor? Running: xm create /cloud/config/hjxmogr553e5jx Using config file “/cloud/config/hjxmogr553e5jx”. Error: Unable to connect to xend: No such file or directory. Is xend running? Fatal: Virtual machine has not been started on hypervisor Executing Rollback… The two possible causes would be the… Read More »