centos

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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CentOS 7 Refusing VMware vSphere Guest OS Customizations

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So I just spent two hours of my life trying to get my CentOS 7 VM template to deploy correctly with a vSphere customization specification. No matter what I did it would customize the VM, then uncustomize it, essentially leaving me with the template again. I finally asked our oracle and savior, Google, and two amazing things occurred. First, I found the answer. About three weeks ago a fellow named Jeff Burns asked this same question on Server Fault, then answered his own question five minutes later (this is often what happens to me immediately upon filing a support case). He built on something I’d seen in /var/log/vmware-imc/toolsDeployPkg.log, where the VMware Tools couldn’t figure out what the OS is and …

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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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Gain 30% Linux Disk Performance with noatime, nodiratime, and relatime

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This is post #8 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” According to Red Hat’s Enterprise Linux 6 Power Management guide, the POSIX family of standards for operating systems “requires that operating systems maintain file system metadata that records when each file was last accessed.” This is called “atime” (a is for access) and is one of three timestamps Linux filesystems keep for their files (the other two are mtime and ctime, modify and change times). You can see these with the ‘stat’ command: $ stat /bin/ls File: `/bin/ls’ Size: 109208 Blocks: 216 IO Block: 4096 regular file Device: fd00h/64768d Inode: 519 Links: 1 Access: (0755/-rwxr-xr-x) …

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Store Logs Centrally

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This is post #7 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” It is universally true that over time a thin-provisioned virtual machine will slowly expand on disk. This happens because of the way files are deleted from disks. When files are written to disk the storage subsystem writes those blocks out, and the thinly-provisioned disk file grows a bit. But when a filesystem deletes a file all it does is update its own internal storage map to “forget” about the file. Nothing ever removes the data from the disk itself (which is why undelete utilities work, and why there are stringent procedures for securely erasing a …

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Use elevator=noop For Linux Virtual Machines

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This is post #6 in my December 2013 series about Linux Virtual Machine Performance Tuning. For more, please see the tag “Linux VM Performance Tuning.” Modern operating systems are fairly modular, and often have different modules to deal with memory, network I/O, and CPU scheduling. Disk I/O is no exception under Linux, as there are usually four different schedulers a sysadmin can choose from. Red Hat had a nice write-up on these a few years back and it remains relevant today: The Completely Fair Queuing (CFQ) scheduler is the default algorithm in Red Hat Enterprise Linux 4. As the name implies, CFQ maintains a scalable per-process I/O queue and attempts to distribute the available I/O bandwidth equally among all I/O …

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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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