Linux and DevOps with Vijay

After rebooting one of our iSCSI based Oracle servers one day, we found ourselves in a bit of a dilemma. Through our cloud vendor's SAN engineering support, we discovered that iSCSI mounted persistence is NOT part of NetApp’s hardware-capable functionality. The engineer also stated that “all existing iSCSI presentations are currently not using multipathing”. Another engineer also stated “relying on them [iSCSI LUNs] to stay the same in my experience is sketchy: It works until it doesn't.” Come to find out it was VMware's upgrade that caused the problem. In the past -- prior to the VMware VM hardware upgrades from version 4 to version 7, the iSCSI devices were mapped in order, even when new LUNs were presented. Now, this is no longer the case. All multiple path’d iSCSI based LUNs are now at risk once upgraded to the new VM hardware version due to the way that VMware realigns the IRQs for the PCI devices. Our 'wonderful' vendor's SAN engineering ...

Syslog-NG Deployment with SSL/TLS Encryption Enabled Syslog-NG is an open source implementation of the Syslog protocol for Unix and Unix-like systems. It extends the original syslogd model with content-based filtering, rich filtering capabilities, flexible configuration options and adds important features to syslog, like using TCP for transport. As of today syslog-ng is developed by Balabit IT Security Ltd. It has two editions with a common codebase. Syslog-NG has a much larger scope than merely transporting syslog messages and storing them to plain text log files: the ability to format log messages using UNIX shell-like variable expansion; the use of this shell-like variable expansion when naming files, thus covering thousands of destination files with a single statement; the ability to send log messages to local applications; ability to message flow-control in network transport; logging directly into a database (since syslog-ng OSE 2.1); rewrite portions of the sys...

Here's quick how-to to add a 40GB VMDK to RHEL/CentOS LVM under ESXi. The same procedures can also be done to physical server environments as well. 1. After you assigned a new disk to the virtual machine you have to add it in the guest and expand the LVM volume. First rescan the SCSI bus to make the kernel detect the new virtual disk: # echo "- - -" > /sys/class/scsi_host/host0/scan   Find out what the new device is called, should be displayed with 'dmesg'. If it is too noisy, you may get what you need with # dmesg | grep sd[abcde]    Similarly type   #fdisk -l 2. # pvscan       This will show you the current physical volumes. 3. # fdisk /dev/sdb       Add the disk to your machine as a primary partition. Partition type: “8e (LVM)”. 4. # pvcreate /dev/sdb1       This creates a new physical LVM volume on our new disk. 5. # vgextend VolGroup00 /dev/sdb1   ...