red hat enterprise linux

How to Install CrashPlan on Linux

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I like CrashPlan. They support a wider range of operating systems than some of their competitors, they have a simple pricing model, unlimited storage & retention, and a nice local, mobile, and web interfaces. I’ve been a customer for a few years now, and recently have switched a few of my clients’ businesses over to them, too. What I don’t like is that they don’t seem to support Linux very well, which is typical of companies when their installed base is mostly Windows & Mac. Most notably, their install instructions are sparse and they don’t tell you what packages you need to have installed, which is important because cloud VMs and whatnot are usually “minimal” installations. I’ve attempted to open …

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Account for the Bandwidth-Delay Product with Larger Network Buffers

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This is post #14 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” At times we can refer to certain network concepts with a “pipe” analogy, where bandwidth is the diameter of the pipe and latency is the length of the pipe. A garden hose has a certain limited amount of “bandwidth” because it has a small interior diameter, and has a lot of latency because it is so long. Water you put in one end of the hose takes a while to come out the other end. A house in the USA likely has a main sewer pipe with 4 inches of “bandwidth” so it can move more, …

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Use Paravirtualized Devices On Your Virtual Machines

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This is post #13 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” para- a prefix appearing in loanwords from Greek, most often attached to verbs and verbal derivatives, with the meanings “at or to one side of, beside, side by side” ( parabola; paragraph; parallel; paralysis ),”beyond, past, by” ( paradox; paragogue ); by extension from these senses, this prefix came todesignate objects or activities auxiliary to r derivative of that denoted by the base word ( parody;paronomasia ), and hence abnormal or defective ( paranoia ), a sense now common in modernscientific coinages ( parageusia; paralexia ). Paravirtual drivers are ones where the virtualization platform does …

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Disk Partition Alignment Is Still Important

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This is post #9 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” I have written about this almost yearly (beginning all the way back in 2006), but even now I routinely run across something, like a virtual appliance, that has poor partition alignment. What’s the big deal? In short, misaligned I/O is killing your disk performance. Blame Logical Block Addressing, or LBA. Back in the day, a BIOS interacted with drives by knowing the exact geometry of the drive, namely how many cylinders, heads, and sectors were on a disk (CHS). Unfortunately that limited the size of the drives that could be used, and ignored some basic …

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Don’t Start GUIs and X Windows On Servers

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This is post #5 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” There are stories out there about system administrators with intermittent performance problems on their Windows servers. Like many problems, it would never happen when the administrator was around, but when they walked away from their servers suddenly the issues would crop up. It was the OpenGL screensaver, sucking up all the CPU. GUIs make life easier sometimes, especially if you aren’t as familiar with an environment as you’d like to be. However, they come at a cost: additional RAM, CPU, and disk overhead. In my travels I’ve seen virtual environments more than double their consolidation …

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Minimal Kickstart File for Red Hat Enterprise Linux 6, CentOS 6, Oracle Linux 6 Virtual Machines

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This is a helper post in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” Here’s a minimal kickstart file for a virtual machine installation of RHEL 6, CentOS 6, or Oracle Linux 6. I use this in conjunction with tools like Puppet and Chef to do the rest of my system configuration. I provision 30 GB thin-provisioned disks to each VM, leaving the rest of it unallocated until needed. While this leads to a disk overcommitment situation that’s manageable, and a tradeoff to ensure more standardization and ease of administration & automation. I remove a number of packages that we don’t necessarily need on a virtual machine, either …

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For The Best Performance Use a Recent Operating System and a Recent Hypervisor

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This is post #1 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” Just like in construction, performance tuning is most effective when you have a good foundation. If the underpinnings of your efforts are weak you won’t be able to build a skyscraper, just a small office building. While that’s still better than nothing, there is often a lot to be gained by using the newest versions of your OS & hypervisor of choice. Some quick examples: Windows Server 2012 R2 added Virtual Receive-side Scaling, which allows the load from network traffic to be processed by multiple virtual CPUs. VMware vSphere 5.5 added support for latency-sensitive VMs, …

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Install the nano Editor on the VMware vMA 5

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The VMware vSphere Management Assistant (vMA) is a handy appliance for interacting with your environment via the Linux command line. I use it a lot, and I’m starting to get more of my team to use it. The problem is that it only ships with the vi text editor, which, described politely, is sort of arcane. Being a UNIX guy I’m used to it, but for others that just want to edit a file it’s overkill. For those situations I like nano, a simple open source editor. To install it on the vMA issue the command: sudo zypper install nano If you’re prompted for a password use the one you set for vi-admin (or whoever you’re logged into the vMA …

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How Large Your Linux Swap Partition Should Be

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This is post #4 in my December-long series on Linux VM performance tuning, Tuningmas. One of those timeless questions in system administration has always been “how much swap space do I configure on my server?” The old rule used to be twice the amount of memory, but does a server with 256 GB of RAM really need a half terabyte of swap? And what about VMs? Swapping on VMs is a serious performance drag. Would it be a good idea to just disable swap completely? One thing to consider is that there’s a tunable kernel parameter, /proc/sys/vm/swappiness, that controls the tendency of Linux to scavenge inactive memory pages and swap them out. It is a number from 0 to 100, …

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Leave Some RAM For Filesystem Cache

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This is post #3 in my December-long series on Linux VM performance tuning, Tuningmas. Many system administrators don’t realize it, but in most OSes RAM that’s unused by applications goes towards filesystem cache, which speeds disk operations. Some VM “right-sizing” tools don’t take this into account, and recommend pretty tight memory allocations which end up causing more disk I/O in the long term. Trading some RAM for better I/O performance is often a very good move, both for an individual VM and for the virtual environment as a whole. To understand what’s happening on a Linux VM and make a decision about how much RAM we should leave for filesystem cache we need to understand the ‘free’ command: total used …

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