Discuss April 2008

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275 discussions

Question about RAID 5 array rebuild with mdadm
by Mark Hennessy 17 Apr '08

17 Apr '08

I'm using Centos 4.5 right now, and I had a RAID 5 array stop because two drives became unavailable. After adjusting the cables on several occasions and shutting down and restarting, I was able to see the drives again. This is when I snatched defeat from the jaws of victory. Please, someone with vast knowledge of how RAID 5 with mdadm works, tell me if I have any chance at all that this array will pull through with most or all of my data. Background info about the machine /dev/md0 is a RAID1 consisting of /dev/sda1 and /dev/sda2 /dev/md1 is a RAID1 consisting of /dev/sda2 and /dev/sdb2 /dev/md2 (our special friend) is a RAID5 consisting of /dev/sd[c-j] /dev/sdi and /dev/sdj were the drives that detached from the array and were marked as faulty. I did the following things that in hindsight were probably VERY BAD Step 1 (Misassign drives to wrong array): I could probably have had things going again in a tenth of a second if I hadn't typed this: mdadm --manage --add /dev/md0 /dev/sdi mdadm --manage --add /dev/md0 /dev/sdi This clobbered the superblock and replaced it with that of /dev/md0, yes? well, that's what mdadm --misc --examine /dev/sdi and sdj said anyhow. Ok, so what next? Step 2 (rebuild the array but make sure the params are right!): I wipe out the superblocks on all of the drives in the array and rebuild with --assume-clean for i in c d e f g h i j ; do mdadm --zero-superblock /dev/sd$i ; done mdadm --create /dev/md2 --assume-clean --level=5 --raid-devices=8 /dev/ sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg /dev/sdh /dev/sdi /dev/sdj ok, now it says that the array is recovering and will take about 10 hours to rebulid. /dev/sd[c-i] say that they are "active sync" and /dev/sdj says it's a spare that's rebuilding. But now I scroll back in my history and see that oops, the chunk size is WRONG. Not only that, but I don't stop the array until the rebuild is at around 8% Ok, I stop the array and rebuild with mdadm --create /dev/md2 --assume-clean --level=5 --chunk --raid- devices=8 /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg /dev/sdh /dev/ sdi /dev/sdj Now it says it's going to take another 10 hours to rebuild. How likely are my data irretrievable/gone and at what step would it have happened if so?

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No Network = slow ??
by Michael A. Peters 17 Apr '08

17 Apr '08

I lost my internet connection earlier today. My home network was still up - it's just the router couldn't get an IP from the cable modem. During that period, my CentOS 5.1 install was extremely slow (2.6 GHz Athlon w/ 2GB ram) at starting non network applications - such as solitare and gnome terminal. It would pause for several seconds before finally starting them. The machine does run bind as a caching nameserver - as I've found that to be more reliable than using my ISPs nameserver, so I'm guessing the slowdown was with bind not being able to resolve anything. Is there anything I can do to prevent the slow application launching in the event of lost network in the future?

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exam txt file
by Hiep Nguyen 17 Apr '08

17 Apr '08

hi all, i have centos 5 w/o gui. i can only have access via ssh. i have a text file that contains special (unprintable) characters, what editor i can use to exam what those character are??? i use vi, but i don't know what is ^@ may be an editor that can show ASCII as dec or hex. thanks

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SSH Question relating to Public and Private Keys
by Clint Dilks 17 Apr '08

17 Apr '08

Hi People, The Linux Environment I am responsible for is using ssh key pairs to allow access to a number or accounts on a number Linux Servers. I currently have the opportunity to re-design some of this. So I would like to tap into peoples experiences to see what might be some good changes to make. Specifically I have a couple of questions 1. Currently all of the key pairs we are using have empty passphrases is it worth the effort of changing this and setting up ssh-agent compared to what you gain in security by doing this ? 2. At this stage I am going to use RSA Keys of the default size, is this generally the best approach? Thanks for any thoughts, and have a nice day :)

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How to Contact Package Maintainer
by Art Age Software 17 Apr '08

17 Apr '08

Hi, I'm wondering what the correct channel is for communicating with the maintainer of a particular package in the Extras repo. Specifically, I would like to find out who maintains the DRBD 8.0.x package, as there is a newer version (8.0.12) that I would like to see added. Or, alternatively, what is the process for suggesting that an out-of-date package be updated in the repo? Thanks! P.S. Apologies if this is a double-post. My first attempt did not seem to go.

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Clamav update error
by Olaf Mueller 17 Apr '08

17 Apr '08

Hello, anyone else seeing this? Resolving Dependencies --> Populating transaction set with selected packages. Please wait. ---> Package clamav-db.i386 0:0.93-1.el5.rf set to be updated ---> Package clamd.i386 0:0.93-1.el5.rf set to be updated ---> Package clamav-milter.i386 0:0.93-1.el5.rf set to be updated ---> Package clamav.i386 0:0.93-1.el5.rf set to be updated --> Running transaction check --> Processing Dependency: libclamunrar_iface.so.3 for package: clamav --> Finished Dependency Resolution Error: Missing Dependency: libclamunrar_iface.so.3 is needed by package clamav regards Olaf

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CONNECTING VIA SSH BETWEEN CENTOS 4 AND 5
by Chris Geldenhuis 16 Apr '08

16 Apr '08

Hi, I am trying to set up an automatic connection between CentOS 4 system (server) and a CentOS 5 DomU VM (client) via ssh to enable my to back up development files on the server to the client with a cron process. I generate they key pair without a pass phrase on the client and copy the public key to the same user's .ssh directory on the server as authorized_keys2. When I try to ssh to the Server from the Client, I am still asked for the user's password on the client. If I do the same with CentOS 5 for both Client and Server, I can login without providing a password. The versions of ssh on the two systems are: Client (CentOS 5): OpenSSH_4.3p2, OpenSSL 0.9.8b 04 May 2006 Server (CentOS 4): OpenSSH_3.9p1, OpenSSL 0.9.7a Feb 19 2003 Does anyone on the list know whether these versions are compatible or how to get them to work together without requiring a password. It is not an option to change to CentOS5 on the server side as that system is serving as a development system for a client running RedHat ES 4 and has to have the identical configuration and be binary compatible. TIA ChrisG

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FreeRadius + Dynamic VLANs/802.1x Authentication
by Matt Shields 16 Apr '08

16 Apr '08

Has anyone setup FreeRadius to do automatic VLAN assignments on their switches based on client mac addresses? If so, would you be willing to share your radius configs? I haven't touched radius since mid 90's and am stuck trying to get this to work. It would be much appreciated. thanks -- -matt

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AWStats included with Centos 5.1 distro?
by Pam Astor 16 Apr '08

16 Apr '08

Hi, Is AWStats included in the Centos 5.1 Distro? _________________________________________________________________ Going green? See the top 12 foods to eat organic. http://green.msn.com/galleries/photos/photos.aspx?gid=164&ocid=T003MSN51N16…

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Centos 5.1 - Xen/ domU related booting questions
by Tomasz Nowak 16 Apr '08

16 Apr '08

Hello, I successfuly run Centos 5.1 domU in Centos 5.1 dom0. But I still have some minor issues/errors/warnings while booting I'd like to fix and here are my questions: 1. How to disable loading usb host controler module: [...from dmesg... ] Loading uhci-hcd.ko module USB Universal Host Controller Interface driver v3.0 insmod: error inserting '/lib/uhci-hcd.ko': -1 No such device Loading ohci-hcd.ko module insmod: error inserting '/lib/ohci-hcd.ko': -1 No such device Loading ehci-hcd.ko module mount: could not find filesystem '/proc/bus/usb' [...] I have extra parameters being passed to kernel in grub: kernel /boot/vmlinuz-2.6.18-53.1.14.el5xen ro root=LABEL=/ console=xvc0 nousb nopcmcia parport=0 but it seems kernel ignores it in domU (works in dom0) 2. How to disable loading floppy detection/support Apr 16 14:03:56 xtest1 kernel: Floppy drive(s): fd0 is unknown type 15 (usb?), fd1 is unknown type 15 (usb?) Apr 16 14:03:56 xtest1 kernel: Failed to obtain physical IRQ 6 Apr 16 14:03:56 xtest1 kernel: floppy0: no floppy controllers found 3. How to disable loading parport/lp modules (parport_pc, parport, lp) Apr 16 14:03:56 xtest1 kernel: lp: driver loaded but no devices found 4. How to setup xm console correctly? While system boots I see: Remounting root filesystem in read-write mode: [ OK ] Mounting local filesystems: [ OK ] Enabling local filesystem quotas: [ OK ] Enabling /etc/fstab swaps: [ OK ] INIT: Entering runlevel: 3 Entering non-interactive startup with no colors. How to make it real console-like, with colors: Remounting root filesystem in read-write mode: [ OK ] Mounting local filesystems: [ OK ] Enabling local filesystem quotas: [ OK ] Enabling /etc/fstab swaps: [ OK ] -- Tomek

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Discuss April 2008