Archive for the ‘Linux’ Category
Do initrd dance before turning Linux physical server into VM
If one day you decide to convert your physical server to a VM, which could be easily achieved if all its disks are presented from SAN, then don’t forget to rebuild initrd beforehand. Otherwise you would see something similar to this: No device found Scanning and configuring dmraid supported devices Scanning logical volumes Reading all […]
Workaround for Tomcat7 on Linux, JDBC and javax.naming.NamingException
A few days ago I was dabbling with JDBC and Tomcat7 and the configuration that seemingly had no issues resulted in the following error in the log file: org.apache.catalina.core.NamingContextListener addResource WARNING: Failed to register in JMX: javax.naming.NamingException: Could not create resource factory instance [Root exception is java.lang.ClassNotFoundException: org.apache.tomcat.dbcp.dbcp.BasicDataSourceFactory] Thankfully, Google pointed me to this post […]
Interview fizzle as a chance to get better
Not a long ago I had one of those humiliating moments when a simple question makes you numb a or even worse – you begin to mumble an absolute rubbish. That is exactly what has happened to me recently and being an afterthought person (which, of course, doesn’t give me any advantage) I decided to […]
Configuring FCoE in Linux (RHEL) and HP FlexFabric
Actually it’s easy. Very easy indeed, like going 1, 2, 3. Collect information about MAC addresses to distinguish pure Ethernet NICs and CNA that will pass FCoE traffic. The latter have both MAC and WWN addresses. Power on a server and update /etc/udev/rules.d/70-persistent-net.rules if required. Activate new dev rules: Install fcoe-utils and lldpad packages: Rename […]
OpenSSL TLS 1.1 and wrong version number
If you, like myself, have been living under a rock you’d be also surprised to know that OpenSSL didn’t support TLSv1.1 and TLSv1.2 until version 1.0.1 . Found out that accidently by trying to disable TLSv1 in Nginx which was running on a RHEL5 box with OpenSSL 0.9.8e. Below is how TLS handshake looked when […]
Linux pptp stumbling blocks that I was hit by
While configuring a pptp on a Linux box I bumped into the several smalish issues which I’d like to blog about. Make sure that your network engineers have enabled traffic inspection on all intermediate firewalls between tunnel’s endpoints. Otherwise LCP won’t be able to finish its configuration negotiation phase even if the control channel on […]
What the heck are all those terms – PV, HVM, HVM with PV drivers, PVHVM, PVH?
If you have to deal with Xen from time to time and not on a permanent basis and want to refresh the difference between all those Xen modes, I strongly encourage everyone to read the following two outstanding articles: The Paravirtualization Spectrum, part 1: The Ends of the Spectrum The Paravirtualization Spectrum, Part 2: From […]
Default Linux I/O multipathd configuration, SCSI timeout and Oracle RAC caveat
I’ve been recently involved in a project to migrate from old and rusty Cisco MDS 9222i to the new MDS 9506 SAN switches and during the first phase of the migration the primary node in a two-node Oracle RAC cluster lost access to its voting disks and went down. And that’s when only half paths […]
Matching Oracle ASM disks names with the physical devices
Quite often it’s required to find a physical device which backs up ASM disk. The easiest way a Linux administrator could accomplish that is by using oracleasm command (of course, if ASMlib was used to create them): # oracleasm listdisks ASMARCHIVE1 ASMARCHIVE2 ASMARCHIVE3 ASMDATA1 ASMDATA2 ASMDATA3 OCR1 OCR2 VOTEDISK1 VOTEDISK2 VOTEDISK3 # oracleasm querydisk -p […]
Openfire. Migrating from HSQLDB to MySQL.
The other day, I had to migtate Openfire from HSQLDB to MySQL using MySQL Migration tool and below just a couple tips that could save a bit of your time if you up to the same task: I used Windowds XP. MySQL Migration tool has been EOLed but it is still available from mysql.com. Java […]