Archive for the ‘Linux’ Category

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 […]

Posted on April 23, 2015 at 12:31 pm by sergeyt · Permalink · 4 Comments
In: Linux

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 […]

Posted on February 20, 2015 at 11:15 am by sergeyt · Permalink · Leave a comment
In: Linux

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 […]

Posted on February 18, 2015 at 9:13 pm by sergeyt · Permalink · Leave a comment
In: Linux

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 […]

Posted on August 22, 2014 at 12:37 pm by sergeyt · Permalink · One Comment
In: FreeBSD, Linux

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 […]

Posted on June 7, 2014 at 4:46 pm by sergeyt · Permalink · One Comment
In: Linux, Oracle

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 […]

Posted on October 8, 2013 at 11:40 pm by sergeyt · Permalink · Leave a comment
In: Linux

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 […]

Posted on August 14, 2013 at 10:24 am by sergeyt · Permalink · Leave a comment
In: Linux

TAO: Facebook’s Distributed Data Store for the Social Graph

This post will be very succinct. Just a single link to a publication of TAO’s details at USENIX and a quote from the abstract part of the paper to catch your eye: We introduce a simple data model and API tailored for serving the social graph, and TAO, an implementation of this model. TAO is […]

Posted on June 27, 2013 at 9:43 am by sergeyt · Permalink · Leave a comment
In: Linux

Simple Python scp wrapper

Inspired by the following article I decided to write a simply python scp wrapper which is based on the ideas taken from the perl script also mentioned on the same page. The whole point of this wrapper is dead simple: to allow certain users scp into their specific directories with out granting full ssh access. […]

Posted on May 28, 2013 at 11:34 am by sergeyt · Permalink · Leave a comment
In: Linux, Scripting

OpenLDAP do_syncrep retrying attempts

Do you observe the error messages on your Linux OpenLDAP replica or master server similar to the ones listed below: May 16 12:05:21 ldapserver1 slapd[5420]: do_syncrep2: rid=005 (-1) Can’t contact LDAP server May 16 12:05:21 ldapserver1 slapd[5420]: do_syncrepl: rid=005 rc -1 retrying (4 retries left) May 16 12:05:21 ldapserver1 slapd[5420]: do_syncrep2: rid=002 (-1) Can’t contact […]

Posted on May 21, 2013 at 9:12 am by sergeyt · Permalink · Leave a comment
In: Linux