Discuss September 2011

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252 discussions

CentOS 6.0: iptables stacktrace with named chains > 28 chars
by Florian CROUZAT 29 Sep '11

29 Sep '11

Hi, I'm not sure where to ask this question, you, redhat or netfilter so I'll ask you guys first, hoping you can redirect me where this post belongs. I have an issue with my CentOS 6 box with named chains in iptables. Apparently there is a builtin #define to limit chain names up to 30 chars, but the test condition fails and iptables crashes with a stacktrace. # cat /etc/redhat-release CentOS Linux release 6.0 (Final) # rpm -qa | fgrep iptables iptables-ipv6-1.4.7-3.el6.x86_64 iptables-1.4.7-3.el6.x86_64 Use cases prove that you can create chains with names up to =30 chars but you can only reference <=28 chars named chains. Trying to reference a 29 or 30 chars named chains will crash iptables. ===== Use cases with 28,29,30 and 31 chars long named chains: # iptables -N $(for((i=0;i<28;i++));do printf "%s" "a";done) && echo ok || echo ko ok # iptables -N $(for((i=0;i<29;i++));do printf "%s" "b";done) && echo ok || echo ko ok # iptables -N $(for((i=0;i<30;i++));do printf "%s" "c";done) && echo ok || echo ko ok iptables -N $(for((i=0;i<31;i++));do printf "%s" "d";done) && echo ok || echo ko iptables v1.4.7: chain name `ddddddddddddddddddddddddddddddd' too long (must be under 30 chars) Try `iptables -h' or 'iptables --help' for more information. ko # iptables -I INPUT -j aaaaaaaaaaaaaaaaaaaaaaaaaaaa && echo ok || echo ko ok # iptables -I INPUT -j bbbbbbbbbbbbbbbbbbbbbbbbbbbbb && echo ok || echo ko <stacktrace> ko # iptables -I INPUT -j cccccccccccccccccccccccccccccc && echo ok || echo ko <stacktrace> ko I can attach strace output or the stacktrace if required. Any infos where to report this issue much appreciated. Florian.

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Finding i/o bottleneck
by Nicolas Ross 28 Sep '11

28 Sep '11

Hi list ! We have a very busy webserver hosted in a clustered environment where the document root and data is on a GFS2 partition off a fiber-attached disk array. Now on busy moments, I can see in htop, nmon that there is a fair percentage of cpu that is waiting for I/O. In nmon, I can spot that the most busy block device correspond to our gfs2 partition where many times, it shows that it's 100% busy and is read all along. Now, I want to know what files are being waited for. With lsof I can get a listing of open files, but it doesn't gives me if a file is just opended in ram or if it's being waited for... What tools besides lsof, nmon, htop, atop can help me find that info ? I am under RHEL/CentOS 6.1. Thanks

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Slow DNS lookups on CentOS6
by Alfred von Campe 28 Sep '11

28 Sep '11

Most of my desktops are still running CentOS5, but I have installed CentOS6 on a few of them. The users on those desktops are reporting that DNS lookups are slow, and from my brief tests, that does appear to be the case. After some googling, I found a suggestion to disable IPv6, but that didn't help. So I tried to figure out where the delay occurs using strace and ltrace, but that didn't help much. When running ltrace, the process I'm trying to trace (host, nslookup) just dies. And the output of strace does show a 3+ second delay, but I can't figure out what it's telling me: 10:46:25.317517 futex(0xd1ba94, FUTEX_WAKE_PRIVATE, 2147483647) = 0 10:46:25.317586 open("/usr/lib/locale/locale-archive", O_RDONLY|O_LARGEFILE) = 6 10:46:25.317635 fstat64(6, {st_mode=S_IFREG|0644, st_size=99158720, ...}) = 0 10:46:25.317702 mmap2(NULL, 2097152, PROT_READ, MAP_PRIVATE, 6, 0) = 0xb569d000 10:46:25.317754 mmap2(NULL, 1171456, PROT_READ, MAP_PRIVATE, 6, 0x19c) = 0xb557f000 10:46:25.317792 mmap2(NULL, 4096, PROT_READ, MAP_PRIVATE, 6, 0x1084) = 0xb557e000 10:46:25.317827 close(6) = 0 10:46:25.317904 futex(0xb76a5050, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xb76a504c, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 10:46:25.317990 futex(0xb76a5018, FUTEX_WAKE_PRIVATE, 1) = 1 10:46:25.318037 rt_sigaction(SIGHUP, {0x141390, ~[RTMIN RT_1], 0}, NULL, 8) = 0 10:46:25.318145 rt_sigsuspend([]) = ? ERESTARTNOHAND (To be restarted) 10:46:28.510794 --- SIGTERM (Terminated) @ 0 (0) --- 10:46:28.510842 sigreturn() = ? (mask now [HUP INT TERM]) 10:46:28.510926 futex(0xb76a5050, FUTEX_WAKE_OP_PRIVATE, 1, 1, 0xb76a504c, {FUTEX_OP_SET, 0, FUTEX_OP_CMP_GT, 10:46:28.511015 futex(0xb76a5018, FUTEX_WAKE_PRIVATE, 1) = 1 10:46:28.511070 futex(0xb76a5050, FUTEX_CMP_REQUEUE_PRIVATE, 1, 2147483647, 0xb76a5018, 18) = 1 10:46:28.511144 futex(0xb76a5018, FUTEX_WAKE_PRIVATE, 1) = 1 10:46:28.511256 futex(0xb769fbd8, FUTEX_WAIT, 2371, NULL) = -1 EAGAIN (Resource temporarily unavailable) 10:46:28.511316 brk(0x920a000) = 0x920a000 The CentOS5 systems on the same network with the same /etc/resolv.conf file do not have these delays. Has anyone else seen this or have some suggestions as to how to debug this? Alfred

7 11

centos 6 console screen
by Jerry Geis 28 Sep '11

28 Sep '11

How do I get the centos 6 console screen out of high-res mode? I tried a couple things of adding to the grub.conf file vga=ask and vga=769. Neither had any effect. I did not get prompted to ask for what mode or anything.... Whats the correct way to have centos 6 drop into normal old vga text mode and not high res small character hard to read mode. Thanks, Jerry

2 1

KVM update
by Johan Martinez 28 Sep '11

28 Sep '11

I am planning to update KVM packages kvm and kvm-qemu-img on a system. Do I need to shutdown running VMs before updating these packages? Does it require any services restart after the update? Any idea? thanks jM

2 1

kickstart: gfx vs. txt mode
by Jure Pečar 28 Sep '11

28 Sep '11

Hello, I seem to recall from my redhat5/6/7 days that certain installation methods used for kickstarting only invoked text mode install. Now I read that graphical install is default in kickstart on el5/6. However, in my test environment (with older HP DL140G3) I only get text mode install up, even if I specify graphical in kickstart file, with both nfs and http install methods. There's no clues on third console, only an info message about display mode being set to 't'. Any clues what am I missing? -- Jure Pečar http://jure.pecar.org http://f5j.eu

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[OT] Fetchmail and Mutt help
by Todd 28 Sep '11

28 Sep '11

Hi All, I setup Fetchmail and wanted to use Mutt to read e-mail. I used to use Pine and I just am sick of GUI e-mail clients these days. Bloat, complication and unreliable. Pine was my first ever e-mail client. I prefer to use POP still as I want may mail on my machine at all times. I can go into mutt and execute: 'fetchmail -v' and watch it bring down my e-mail. But in mutt i dont see anything. I dont see an inbox. no messages. nada. I set my mail to /Users/jtsm/.mail and if I go to that location I dont see anything there. Can anyone help me get setup? Also, can anyone point me how to make mutt look like this: http://linsec.ca/File:Muttscreen.jpg interms of the columns? IIRC there use to be a patch but that was so long ago I dont know if it even applies anymore. I am reading the Wiki, but who knew Mutt was so extensive... -Todd

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Please remove the formation about RAQport it is incorrect
by Alex Bajan 28 Sep '11

28 Sep '11

Please remove the formation about RAQport it is incorrect http://lists.centos.org/pipermail/centos/2007-September/043643.html Alex Lech Bajan Principal RAQport Inc. 2004 North Monroe Street Arlington Virginia 22207 703-528-0114 voice 703-652-0993 voice 2 800-695-6200 toll free sales(a)raqport.com http://raqport.com

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CentOS-6 by PXEboot?
by Timothy Murphy 27 Sep '11

27 Sep '11

Has anyone succeeded in installing CentOS-6.0 by PXEboot. If so, would you say how you did it, please. I tried (on an HP MicroServer), but gave up in the end and used a USB stick installation instead. But I'd be very interested to know how to do it, for the future. Unfortunately I didn't keep a proper note of my PXEboot attempt, but IIRC the problem was that install.img was not found, although I had links to it in several places. -- Timothy Murphy e-mail: gayleard /at/ eircom.net tel: +353-86-2336090, +353-1-2842366 s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland

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problem in cr: nfs-utils-lib-1.1.5-3.el6.x86_64
by Paul Heinlein 27 Sep '11

27 Sep '11

I ran yum update on a CentOS 6.0 machine against the CR repository and noticed that the nfs-utils-lib update broke my rcp.idmap settings: rpc.idmapd: libnfsidmap: processing 'Method' list rpc.idmapd: libnfsidmap: Unable to get init function: /usr/lib64/libnfsidmap/umich_ldap.so: undefined symbol: libnfsidmap_plugin_init rpc.idmapd: libnfsidmap: requested translation method, 'umich_ldap', is not available rpc.idmapd: Unable to create name to user id mappings. The /usr/lib64/libnfsidmap/umich_ldap.so library included with the 1.1.5-3.el6 update is noticably smaller than the one included in the standard 6.0 package, v. 1.1.5-1.el6. The rpm checks out correctly via gpg and an rpm2cpio->cpio pipe. Running ldd against the updated library shows the expected links. But the library appears to not work. Anyone else seen this? -- Paul Heinlein <> heinlein(a)madboa.com <> http://www.madboa.com/

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Discuss September 2011