Discuss September 2013

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139 participants
128 discussions

heavy IO load when working with sparse files (centos 6.4)
by Ron E 31 Mar '15

31 Mar '15

Dear List, We have noticed a variety of reproducible conditions working with sparse files on multiple servers under load with CentOS 6.4. The short story is that processes that read / write sparse files with large "holes" can generate an IO storm. Oddly, this only happens with holes and not with the sections of the files that contain data. We have seen extremely high IO load for example copying a 40 or 80gb sparse file that only has a few gigs of data in it. Attempts to lower the io priority and cpu priority of these processes do not make any measurable difference. (ionice, nice) This has been observed with processes such as: cp rsync sha1sum The server does have to be under some load to reproduce the necessary conditions. The cases we have seen involve servers running 10-30 guests under kvm. Load is in acceptable norms when the processes are run, such as load avg 5-15 on a 24 core (12 core with HT enabled) server. We also verify before starting such a process that the spindle with the file we're working on is not being unduly hammered by another process. These servers have one hardware raid controller each (Dell H700 controller with write cache enabled) and multiple raid arrays (separate sets of physical spindles). Interestingly, the IO storm is not limited to the array / spindles where the sparse file resides but affects all IO on that server. We have looked extensively and not found any account of a similar issue. We have seen this on configurations that are 'plain vanilla' enough to think that this is not something specific to our environment. Wondering if anyone else has seen this and if any suggestions on gathering more data / troubleshooting. We wonder if we've found either a raid controller driver issue, an OS issue or some other such thing. What seems to point in this direction is that even with ionice -c3 which should prevent the process from using IO unless the storage is idle, an io storm which appears to saturate the entire raid bus on a given server can occur. Thanks in advance.

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Centos 6.4 on Xserve, IPMI error
by Arno B 31 Mar '15

31 Mar '15

Hello! I'm trying to install Centos 6.4 64 bit on this Xserve: http://www.everymac.com/systems/apple/xserve/specs/xserve-intel-xeon-2.8-ei… I got a bootloader from: http://blog.christophersmart.com/2009/07/23/linux-on-an-apple-xserve-efi-on… as none of the official Centos releases (full, minimal, network 64 bit) boot on this machine. They all crash when loading the bootx64.conf. I have built a USB stick with a working bootx64.efi, grub.cfg, together with an initrd and a vmlinuz from the isolinux folder. These seem to get me into booting a kernel until something called IPMI is starting to throw errors at me: Console: switching to colour frame buffer device 128x48 fb0: VESA VGA frame buffer device ipmi message handler version 39.2 IPMI System Interface driver. ipmi_si 0000:09:00.4: enable device (0002 -> 0003) ipmi_si 0000:09:00.4: PCI INT C -> GSI 16 (level, low) -> IRQ 16 ipmi_si: Adding PCI-specified kcs state machine ipmi_si 0000:09:00.7: enable device (0000 -> 0003) ipmi_si 0000:09:00.7: PCI INT D -> GSI 17 (level, low) -> IRQ 17 ipmi_si: Adding PCI-specified bt state machine ipmi_si: Trying PCI-specified kcs state machine at mem address 0x90841000, slave address 0x0 irq 16 IRQ 16/ipmi_si: IRQF_DISABLED is not guaranteed on shared IRQs Using irq 16 ipmi: Found new BMC (man_id: 0x00003f, prod_id: 0x0003, dev_id: 0x20) IPMI kcs interface initialized ipmi_si: Trying PCI-specified kcs state machine at mem address 0x90840000, slave address 0x0 irq 17 Refined TSC clocksource calibration: 2792.999 MHz. Switching to clocksource tsc IPMI BT: timeout in XACTION [ B_BUSY ] 1 retries left IPMI BT: timeout in XACTION [ B_BUSY ] failed 2 retries, sending error response IPMI: BT reset (takes 5 secs) IPMI BT: timeout in XACTION [ B_BUSY H2B ] failed 2 retries, sending error response IPMI: BT reset (takes 5 secs) IPMI BT: timeout in XACTION [ B_BUSY H2B ] failed 2 retries, sending error response IPMI: BT reset (takes 5 secs) IPMI BT: timeout in XACTION [ B_BUSY H2B ] failed 2 retries, sending error response IPMI: BT reset (takes 5 secs) IPMI BT: timeout in XACTION [ B_BUSY H2B ] failed 2 retries, sending error response IPMI: BT reset (takes 5 secs) then the screen goes to black and the machine doesn't respond to anything anymore... Can anyone please help me with this? Maybe just point me in a direction where to find a solution? I've been googling for a few days now without much results... thanks in advance Arno Beekman

2 1

mixing MX and CNAME
by aurfalien 27 Aug '14

27 Aug '14

Hi, Has any one had problems with mail clients were your DNS is like this; doman.com MX 50 mail.domain.com domain.com MX 100 mail2.domain.com domain.com CNAME www.domain.com -aurf

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RH developer toolset
by Jerry Geis 13 Aug '14

13 Aug '14

I saw an article this morning about the RH developer toolset. basically it includes a couple of packages like PHP python mysql (etc) that are later packages than that included in the released version like a 6.4 for example. So instead of php 5.3 with patches it would be php 5.4 and so on. That is great for a couple packages - but what about more up to date libraries like glib. 6.4 is way behind on glib. Like a couple years behind. Are there any plans in the "toolset" to update core libraries also? Thanks, Jerry

6 6

Create Virtual Machine via HTTP or FTP
by cbulist＠gmail.com 08 Jun '14

08 Jun '14

Hi, I'm trying to create a Virtual Machine using Network Install mode (I tried HTTP and FTP). The HTTP/FTP server where the installation files are located is the Host Machine. The URL that I'm using is: http://192.168.1.104/inst and the Automatic detect option detects the OS without problem. When the installation starts I got an error: Unable to retrieve http://192.168.1.104/inst/images/install.img I tried different path but I always get the same error. The host machine is a Centos 6.2 (2.6.32.-220.el6.x86_64) I really appreciate any help with this problem. Thanks in advance,

5 7

idea: "hybrid" iso images?
by Joseph Spenner 30 Jan '14

30 Jan '14

In order to create a bootable CentOS installation USB thumb drive, there are several steps one must follow. The process often involves using a Windows box, which can be kinda annoying. The Linux Mint distro has what they call a "Hybrid" iso image. (see: http://community.linuxmint.com/tutorial/view/744 ) This image can be written to a thumb drive and used for installation simply by performing: # dd /path/to/image.iso of=/dev/sdb (where /dev/sdb is the thumb drive device). This thumb drive can now be booted and used for installation. The same image.iso file can be written to CD/DVD to create the installation media as well. Is this a complicated ISO build process? I'm frequently installing to systems without CD/DVD drives, so this would come in handy. Thanks! Regards, Joseph Spenner ______________________________________________________________________ If life gives you lemons, keep them-- because hey.. free lemons. "♥ Sticker" fixer: http://microflush.org/stuff/stickers/heartFix.html

4 6

Old hardware, newer kernels
by Ashley M. Kirchner 30 Nov '13

30 Nov '13

I have an old server (old hardware) that's been running 6.4 with kernel 2.6.32-279.19.1.el6.i686, no problem. Except, any kernel update after that causes it not to boot anymore. All I get is a blinking cursor on the screen, nothing else. Is this the end of this hardware, no more kernel updates after this? For reference, these are all the options that kernel is booting up with (lines wrapped on purpose): title CentOS (2.6.32-279.19.1.el6.i686) root (hd0,0) kernel /boot/vmlinuz-2.6.32-279.19.1.el6.i686 ro \ root=UUID=3f79e6b6-7845-499f-b708-aef782602673 rd_NO_LUKS rd_NO_LVM \ rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 \ KEYBOARDTYPE=pc KEYTABLE=us noapic apm=off ide=nodma acpi=off \ crashkernel=auto rhgb quiet selinux=0 initrd /boot/initramfs-2.6.32-279.19.1.el6.i686.img

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nfs4, idmapd, users with same name, different uid?
by Les Mikesell 22 Nov '13

22 Nov '13

Is idmapd supposed to work where users have different uid numbers on the nfsv4 server and client? It seems to show the right names for ownership on the client side, but if I automount a home directory, that user doesn't have permission to enter it, and if I change permission to allow access and create a new file, it shows on the server as owned by the uid number for the user on the client (and wrong on the server). Everything works like it would on nfs v3 where the uid numbers are the same on the client and server, but what's the point of the rpcidmapd daemon if it doesn't actually map the ids? -- Les Mikesell lesmikesell(a)gmail.com

5 12

Overheating on laptop as compared to RHEL
by Krishnan V 16 Oct '13

16 Oct '13

Hi, I have an acer 5738g laptop on which i tried out the centos6.4 live CD. The laptop feels noticable hotter and i check the temperature using something like cat /proc/acpi/thermal_zone/. The temperatures are around 57-60 degrees when the laptop is just idling, ie, just the desktop and the terminal window open. I install lm_sensors using yum and it installs successfully, but there is no noticable reduction in temperature. I have faced this same problem using different varities of gnu/linux distributions: slackware, lubuntu, mandriva and now centos. By a freak chance, i had a chance to run RHEL 5.4 and to my great surprise, the temperature at idling was 43, similar to Windows(which came as default). In fact, the temperature control by rhel was what made me think of trying centos. I tried the lm_sensors configuration on rhel and it was not even able to load the correct modules, yet the temperature control was better. Now, i am not sure if lmsensors are for detecting temperatures only but also for cotrolling temperature. I am also aware that this particular model is notorious for heating problems, and there are suggestions for cutting case for better air flow. However, i do not want to try this solution, but the temperature control by rhel gave me some hope! Posibly i am wrong. If anyone has a suggestion, or needs more information, pl. let me know. Thanks! Krishnan

3 5

Best configuration for encrypted software RAID 1?
by Dave Johansen 10 Oct '13

10 Oct '13

I'm setting up a computer with CentOS 6.4 and a mirrored software RAID. I would like it to be encrypted so I was wondering what the best configuration is. The only info I could find is http://lists.centos.org/pipermail/centos-docs/2008-October/001912.html but it appears to be a bit old and the info on the wiki ( http://wiki.centos.org/HowTos/EncryptTmpSwapHome ) doesn't seem to address RAIDs. My main question is will it be better to encrypt the RAID itself or the two partitions used by the RAID? Any other things I should be aware of? Thanks, Dave

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Discuss September 2013