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Some RAID-6 observations ... RHEL-6 vs CentOS-5.5
by Chuck Munro 10 Feb '11

10 Feb '11

Hello all, In the process of building a new VM box to replace several individual CentOS servers, I've had the "interesting" experience of running both CentOS-5.5 and RHEL-6 (eval copy) as I build out the hardware based on a Supermicro motherboard. A couple of observations regarding RAID-6: - RAID-6 arrays created on RHEL-6 don't seem backward compatible with CentOS-5.5. This may or may not be expected behaviour, but it makes me wonder if forward compatibility might be a problem for those of us migrating large RAID-6 arrays from CentOS-5 to -6 systems. The main observations are that the md superblock is declared bad, and I get those boot-time messages claiming the available blocks are less than the configured size. As a result, the RAID arrays are not made available on CentOS-5.5. - A total of 8 RAID-6 arrays in RHEL-6 are built with 2TB data disks plus a hot spare. However, every time I boot the system some, but not all, of the hot spare partitions are randomly missing. Using mdadm to manually add the spare partition back into an array always works. There are 4 array partitions per disk, and the largest single array is just over 2 TBytes of useable space. There are two groups of 5+1 drives spread across two SAS/SATA controller cards, and this random behaviour can occur on either one. Rebooting gets me a different set of missing hot spare partitions. The only error messages I get are the mdmonitor "missing spares event" emails ... nothing in dmesg. The host OS has its own RAID-1 (+ hot spare) arrays on a separate set of disks and controller, and those arrays always come up correctly. I've checked and double ckecked the mdadm.conf file to make sure the ARRAY, DEVICE and 'devices=....' statements are correct. Using mdadm to shut down an array and then reassemble it always seems to work properly, but something random is happening at boot-time assembly. It's only the hot spare partitions that don't appear, never the data partitions. Weird. I'm hoping CentOS-6 doesn't present me with the same problem. Because I'm not a registered RHEL user, I don't have the ability to submit a bug report at RedHat. Chuck

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dhcp fail over
by aurfalien＠gmail.com 10 Feb '11

10 Feb '11

Hi all, Few questions. Does DHCP failover work with statically assigned nodes? Seems like the failover statements only work in shared networks with non bootp clients? I'm assuming Centos 6 will have DHCP v4.2? Currently 5.5 ships with v3.0.5b. And will DHCP v4.X have easier failover implementation? Thanks in advance, - aurf

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High Availability and Storage Cluster
by Denis Zaharov 10 Feb '11

10 Feb '11

Dear mailing list members, There was a branch about clusters, but I have a certain task. There are two servers with CentOS 5.5 installed. The servers are working with Zabbix (monitoring system for traffic, using a MySQL), wiki and RT (all are using Apache). If one server will have became not available then necessary start these services on another server with replication of data. Can I use the Red Hat Cluster Suite for it at CentOS? Also I heard about Heartbeat and DRBD. Maybe it is what I need? -- Kind regards, Denis Zaharov

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PAE kernel source code
by sri 10 Feb '11

10 Feb '11

Hi I want to use 2.6.18-194.el5-PAE kernel source code. Unable to find it over web. Appreciate any pointers for that. Thanks, Sri -- --

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ipsec with ipv4 and ipv6 not working
by Steve Clark 10 Feb '11

10 Feb '11

Hello, How do I find out what is happening to my packets thru my ipsec tunnel. They just seem to disappear on the remote side. I have successfully got the pings thru when everything has an ipv6 address, but am not successful when trying to connect two ipv4 lans across an ipv6 ipsec tunnel. All fw chains both 4 and 6 are set to ACCEPT. NAT is turned off. eth0 eth1 eth1 eth0 10.1.254.254/17 2001:xxxx:1628::254 <----ipv6 internet -----> 2001:xxxx:e334::254 10.0.254.254/17 12:00:02.296972 IP6 2001:xxxx:1628::254 > 2001:xxxx:e334::254: ESP(spi=0x07454bc3,seq=0x28b), length 132 12:00:03.308751 IP6 2001:xxxx:1628::254 > 2001:xxxx:e334::254: ESP(spi=0x07454bc3,seq=0x28c), length 132 12:00:04.296857 IP6 2001:xxxx:1628::254 > 2001:xxxx:e334::254: ESP(spi=0x07454bc3,seq=0x28d), length 132 12:00:05.293748 IP6 2001:xxxx:1628::254 > 2001:xxxx:e334::254: ESP(spi=0x07454bc3,seq=0x28e), length 132 12:00:06.296623 IP6 2001:xxxx:1628::254 > 2001:xxxx:e334::254: ESP(spi=0x07454bc3,seq=0x28f), length 132 I have posted to the ipsec-devel list and haven't gotten any responses. Also I have spent 2 days googling with no results about the above setup. Is it even possible to tunnel ipv4 packet thru an ipv6 ipsec tunnel? Thanks, Steve -- "They that give up essential liberty to obtain temporary safety, deserve neither liberty nor safety." (Ben Franklin) "The course of history shows that as a government grows, liberty decreases." (Thomas Jefferson)

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VPN inside VPN?
by Fajar Priyanto 10 Feb '11

10 Feb '11

Hi all, Just wondering if VPN inside VPN is possible? I've created PPTP VPN in the office. Then from home, first I need to use company's official AT&T VPN. Then after connected, I fire up the PPTP VPN client. Got connected, but cannot ping the PPTP gateway, and half minute later the PPTP got disconnected. No obvious error message in the PPTP log. Thank you.

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Re: [CentOS] Ken Olsen od DEC, 1927-2011
by Les Bell 09 Feb '11

09 Feb '11

Raymond Lillard <ryl(a)sonic.net> wrote: >> The statement is generally quoted without context as it is here. << Correct. Olsen is also famous for saying "People will get tired of managing personal computers and will want instead terminals, maybe with windows." (by which he meant, a windowing graphical terminal, a la X). He was right about that; witness the popular disenchantment with MS Windows and its endless cycle of patching, upgrades, malware removal and registry cleanup, and the fascination with cloud services accessed by lightweight clients like netbooks, tablets and phones. That's been good for the Linux and Centos communities, who have provided low-maintenance services for clients both on the desktop and in the cloud. I venture to say that DEC was an influence on many of the old hands here and on other lists. The PDP-8 was the first computer I actually got my hands on (as opposed to being walked through the machine room and told "Don't touch anything! This is where your code gets compiled and run - careful with the card deck on top of that tape drive behind you!"). And later, I found myself teaching business students to program on a PDP-11/70 running RSTS/E. DEC was certainly heavily influential in our industry, both directly and indirectly, and Olsen was - of course - hugely influential on DEC. Best, --- Les Bell [http://www.lesbell.com.au] Tel: +61 2 9451 1144

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a possible heads up wrt CERN experiment breaking SL 5.6
by Larry Vaden 09 Feb '11

09 Feb '11

This may or may not be of interest to CentOS developers; if it is not or if it is redundant of your efforts to keep atop of what's happening, you have my apologies. Whether it is joint or disjoint wrt to the upstream code is not known at this point, but I have submitted a request for elucidation if CERN security allows. kind regards/ldv ---------- Forwarded message ---------- From: Ewan Mac Mahon <ewan(a)macmahon.me.uk> Date: Wed, Feb 9, 2011 at 10:11 AM Subject: SL 5.6 released? To: SCIENTIFIC-LINUX-USERS(a)fnal.gov Hi, As far as I'm aware SL 5.6 isn't out yet - I don't think I've seen a release announcement, it's not on ftp.scientificlinux.org, and the web site front page lists 5.5 as the latest, and SL 6 was being considered a higher priority. However, someone from CERN IT (discussing some experiment software which seems to break on 5.6) has just told a grid deployment meeting that: "FNAL released SL 5.6 last week" Clearly either my understanding is flawed or his is; which is it please? Ewan

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mount the wrong device after system recovery
by Xinhuan Zheng 09 Feb '11

09 Feb '11

Hi, I am recovering a CentOS 5.4 system. I've copied all partitions into the recovery system. I've installed grub boot loader. However, the original system is using /dev/sdb1 for root (/), while the recovery system is using LVM (/dev/vg0/lv1) for root (/). When recovery system boots, I got the panic error: * Mounting /dev/sdb1 on /sysroot * Mount: mounting /dev/sdb1 on /sysroot failed: No such file or directory * Mount: mounting /dev on /sysroot/dev failed: No such file or directory * * switching / to /sysroot * Switch_root: bad newroot /sysroot * Kernel panic - not syncing: Attempted to kill init! I've changed the recovery system fstab to use the correct devices. I deleted recovery system etc/lvm/cache/.cache file. But it still doesn't work. What am I missing? Thanks, - xinhuan

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iptables nat table rules
by Carlos S 09 Feb '11

09 Feb '11

I am forwarding traffic on port 8080 to port 80 with following rule. # iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 8080 -j REDIRECT --to-port 80 # iptables-save However, I am unable to add it directly in /etc/sysconfig/iptables. I think it is used only for filter table and not nat table. So where do nat table rules go? Any help? - cs.

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