Discuss May 2015

discuss@lists.centos.org

140 participants
129 discussions

CentOS 7, NFS 4, and a non ext4 fs (like zfs)
by tballin 05 May '15

05 May '15

Hello, we want to migrate to CentOS 7(.1) , Server, Client etc ... Right now we need to suspend that because we have some serious issues with NFS4 shared ZFS ( kernel module - zfs on linux project ) Volumes and CentOS 7 clients. Our current server are CentOS6.5, if we share a zfs volume and do the following on this share: client A reads/access file "z.txt". Now client B replaces (copy, move, unlink+link ) files "z.txt" with a new different version and now client A reads/access the file "z.txt" ( and only the file - do not do anything which does a "stat" on the file e.g. "cat z.txt") the old version/content is read. As long as you do something that issues a "stat" for the file/dir. This is really a problem because a soon you are not browsing through the dirs e.g. updating some scripts or anything automated the changes are not recognized by the client. This does not happen with a ext4 share. This also happen with a centos7.0 NFS Server and ZFS/XFS. We permute pretty much every nfs mount/share option - it always happens. Nothing does help. This does not happen with a Centos7.1 server and a centos7.1 client and xfs (NFS4.1). Of course it works with our current client server Version: Ubuntu 12.04 / CentOS 6.5. It really does not seem to be a zfs issue - it does look more like a nfs problem with certain filessystems. I asked this already on the zfs mailing list. So is there something I can do? Is the problem known? Is there a workaround , patch or fix? I am still unsure if I missed something completely because the problem is just so serious... With kind regards Timo Ballin ____ ESET 11570 (20150504) ____ The message was checked by ESET Mail Security.

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odd characters centos 7.1
by Jerry Geis 05 May '15

05 May '15

When I am removing files or copying files and getting prompted to overwrite or am I sure... I get these odd characters rm: remove regular file âfileâ? What is that from? my TERM is xterm as I am "ssh'ed" into a machine. Thanks, Jerry

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IPTABLES question
by James B. Byrne 05 May '15

05 May '15

Would someone please explain to me the difference in effect between the following two IPTABLES conditions and the significance thereof in concurrent connection limiting? --tcp-flags SYN,ACK,FIN,RST SYN -j REJECT \ --connlimit-above 3 --connlimit-mask 32 --state NEW -j REJECT \ --connlimit-above 3 --connlimit-mask 32 -- *** e-Mail is NOT a SECURE channel *** Do NOT transmit sensitive data via e-Mail James B. Byrne mailto:ByrneJB@Harte-Lyne.ca Harte & Lyne Limited http://www.harte-lyne.ca 9 Brockley Drive vox: +1 905 561 1241 Hamilton, Ontario fax: +1 905 561 0757 Canada L8E 3C3

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Last few days in CentOS
by Karanbir Singh 05 May '15

05 May '15

Last few days in CentOS : * We have now got a 5 machine armv7 ( 32 bit ) Buildsystem running. Over the coming days and weeks you should keep an eye out for testing calls. If you can, and have interesting ARM hardware, feel free to join us at the arm-dev list ( http://lists.centos.org/pipermail/arm-dev/ - more information on the build system can be found in this thread: http://lists.centos.org/pipermail/arm-dev/2015-April/000126.html * There is a lot of work being done to get XFCE in a good state for CentOS-6 and 7, you can track the conversation from this thread http://lists.centos.org/pipermail/centos-devel/2015-May/013326.html * The RDO Project is running 2 test days for OpenStack on CentOS. You can get details and join the effort ( it rsun 5th and 6th May ) at http://lists.centos.org/pipermail/centos-devel/2015-April/013309.html * There is a Vagrant Box now available for CentOS, for user testing and feedback - if you use Vagrant on VirtualBox or Livbirt or vmware backends, please give this a try and send feedback to the centos devel list ( more info at : http://lists.centos.org/pipermail/centos-devel/2015-April/013297.html )ifou Events: * We had a great CentOS Dojo at Bangalore, India on the 29th April. About 70 CentOS users came together to talk about containers. Details of the meeting are at http://www.meetup.com/CentOS-India/events/221769525/ and you can see some pictures at https://www.flickr.com/photos/saifikhan/sets/72157649944407033/ * OpenStack Summit is happening at Vancouver, CA from May 18th to 22nd. CentOS Project will have a presence there. If you are coming to the event, stop by and say hi! We will also have tshirts and stickers, so come along and help yourself to some of those. * Netherlands UUG Spring Conference is taking place on the 28th May, ( https://www.nluug.nl/index.html ) I will be there speaking about CentOS Linux, The CentOS project and some of the new innitatives we are starting up, along with how people can get involved in these efforts. In other news, 7 students have taken up the Google Summer of Code slots that were allocated to the CentOS Project, over the next few weeks expect to see some traffic on centos-devel list from those students - and we will be encouraging them to come and join the various SIG meetings and communicate outward their progress, and also ask for help if they get stuck in anywhere. They will be working on things ranging from Kpatch live patching, to Xen and Cloud installs, to improving our documentation trails! I'm very excited to have these students onboard! Hope they have a great summer ahead and produce some great code. Regards, -- Karanbir Singh +44-207-0999389 | http://www.karan.org/ | twitter.com/kbsingh GnuPG Key : http://www.karan.org/publickey.asc

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question about unhide / transitory process
by Ulrich Hiller 05 May '15

05 May '15

Hello, running unhide ( unhide-20130526-1.el7.x86_64 ) on CentOS 7 i get sometimes messages like: Found HIDDEN PID: 30784 Cmdline: "<none>" Executable: "<no link>" "<none> ... maybe a transitory process" On a second unhide run immediately after it, the process seems to have vanished. Also, i do not see anything about it in /proc, and rkhunter and chkrootkit do _not_ detect it. How can i debug or do some further tests? I want to make sure that this is a false positive and not a rootkit. Thanky a lot in advance, ulrich

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Mysql 5.6, Centos 7 and errno: 24 - Too many open files
by Götz Reinicke - IT Koordinator 05 May '15

05 May '15

Hi, may be somewon has a working solution and information on that: I installed the most recent mysql community on a server and do get a lot of "errno: 24 - Too many open files". There are suggestions to increase the open_files_limit, change/add that to /etc/security/limits.conf and modify the systemd script by hand. Depending on how you start mysql (restart, or at systemboot time ...) the limit get set or not. Question: Is that may be a known bug or something? And thats mit a question regarding mariadb or mysql. Regards . Götz -- Götz Reinicke IT-Koordinator Tel. +49 7141 969 82 420 E-Mail goetz.reinicke(a)filmakademie.de Filmakademie Baden-Württemberg GmbH Akademiehof 10 71638 Ludwigsburg www.filmakademie.de Eintragung Amtsgericht Stuttgart HRB 205016 Vorsitzender des Aufsichtsrats: Jürgen Walter MdL Staatssekretär im Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg Geschäftsführer: Prof. Thomas Schadt

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syncookies.c
by Ibrahim Celikbilek 05 May '15

05 May '15

Default,syncookies are activate when syn list(backlog queue) is full. I want hybrid system. I propose a system , syncookies active dynamic per connection . where will I write code , where syncookies system does call in the code file.

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Re: [CentOS] nfs (or tcp or scheduler) changes between centos 5 and 6?
by Peter van Hooft 04 May '15

04 May '15

> Message: 4 > Date: Wed, 29 Apr 2015 08:35:29 -0500 > From: Matt Garman <matthew.garman(a)gmail.com> > To: CentOS mailing list <centos(a)centos.org> > Subject: [CentOS] nfs (or tcp or scheduler) changes between centos 5 > and 6? > Message-ID: > <CAJvUf-CyTg8ZiGq3OXRLKw7s1K2dGx1gqo_2XwOAXXQty=RHZQ(a)mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > We have a "compute cluster" of about 100 machines that do a read-only > NFS mount to a big NAS filer (a NetApp FAS6280). The jobs running on > these boxes are analysis/simulation jobs that constantly read data off > the NAS. > > We recently upgraded all these machines from CentOS 5.7 to CentOS 6.5. > We did a "piecemeal" upgrade, usually upgrading five or so machines at > a time, every few days. We noticed improved performance on the CentOS > 6 boxes. But as the number of CentOS 6 boxes increased, we actually > saw performance on the CentOS 5 boxes decrease. By the time we had > only a few CentOS 5 boxes left, they were performing so badly as to be > effectively worthless. > > What we observed in parallel to this upgrade process was that the read > latency on our NetApp device skyrocketed. This in turn caused all > compute jobs to actually run slower, as it seemed to move the > bottleneck from the client servers' OS to the NetApp. This is > somewhat counter-intuitive: CentOS 6 performs faster, but actually > results in net performance loss because it creates a bottleneck on our > centralized storage. > > All indications are that CentOS 6 seems to be much more "aggressive" > in how it does NFS reads. And likewise, CentOS 5 was very "polite", > to the point that it basically got starved out by the introduction of > the 6.5 boxes. > > What I'm looking for is a "deep dive" list of changes to the NFS > implementation between CentOS 5 and CentOS 6. Or maybe this is due to > a change in the TCP stack? Or maybe the scheduler? We've tried a lot > of sysctl tcp tunings, various nfs mount options, anything that's > obviously different between 5 and 6... But so far we've been unable to > find the "smoking gun" that causes the obvious behavior change between > the two OS versions. > > Just hoping that maybe someone else out there has seen something like > this, or can point me to some detailed documentation that might clue > me in on what to look for next. > > Thanks! > You may want to try reducing sunrpc.tcp_max_slot_table_entries . In CentOS 5 the number of slots is fixed: sunrpc.tcp_slot_table_entries = 16 In CentOS 6, this number is dynamic with a maximum of sunrpc.tcp_max_slot_table_entries which by default has a value of 65536. We put that in /etc/sysconfig/modprobe.d/sunrpc.conf: options sunrpc tcp_max_slot_table_entries=128 You can't put this in /etc/sysctl.conf because the sunrpc kernel module is loaded before sysctl -p is done. peter

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Could not complete SSL handshake to Amazon EC2 host
by Tim Dunphy 04 May '15

04 May '15

Hello, I am trying to monitor a host in the Amazon EC2 cloud. Yet when I try to check NRPE from the monitoring host I am getting an SSL handshake error: [root@monitor1:~] #/usr/local/nagios/libexec/check_nrpe -H ops.jokefire.com CHECK_NRPE: Error - Could not complete SSL handshake. And if I telnet into the host on port 5666 to see if the FW port is open, the connection closes right away: [root@monitor1:~] #telnet ops.somewhere.com 5666 Trying 54.225.218.125... Connected to ops.somewhere.com. Escape character is '^]'. Connection closed by foreign host. You can see there it connects, but then it closes immediately after the connection. I have NRPE running on the host I want to monitor: [root@ops:~] #lsof -i :5666 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME xinetd 1434 root 5u IPv4 4063 TCP *:nrpe (LISTEN) And I have the IP of my nagios server listed in the xinetd conf file: [root@ops:~] #cat /etc/xinetd.d/nrpe # default: on # description: NRPE (Nagios Remote Plugin Executor) service nrpe { flags = REUSE socket_type = stream port = 5666 wait = no user = nagios group = nagios server = /usr/local/nagios/bin/nrpe server_args = -c /usr/local/nagios/etc/nrpe.cfg --inetd log_on_failure += USERID disable = no only_from = 127.0.0.1 xx.xx.xx.xx # <- representing my real nagios server IP } And I have my default security group for that host open on port 5666 to the world for this experiment. I plan on locking that down again to the single IP of my monitoring host once I get this resolved. Does anyone have any suggestions on how I can get that problem solved? Thanks, Tim -- GPG me!! gpg --keyserver pool.sks-keyservers.net --recv-keys F186197B

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can't disable tcp6 on centos 7
by Tim Dunphy 04 May '15

04 May '15

hey all, I tried disabling tcp v6 on a C7 box this way: [root@puppet:~] #cat /etc/sysctl.conf # System default settings live in /usr/lib/sysctl.d/00-system.conf. # To override those settings, enter new settings here, or in an /etc/sysctl.d/<name>.conf file # # For more information, see sysctl.conf(5) and sysctl.d(5). net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 Then going: [root@puppet:~] #sysctl -p net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 Then I restarted xinetd for good measure: [root@puppet:~] #systemctl restart xinetd [root@puppet:~] # Because I'm trying to hit nrpe on this host. Yet, xinetd/nrpe still seems to be listeing on TCP v6!! [root@puppet:~] #netstat -tulpn | grep -i listen | grep xinetd tcp6 0 0 :::5666 :::* LISTEN 2915/xinetd This is a CentOS 7.1 box: [root@puppet:~] #cat /etc/redhat-release CentOS Linux release 7.1.1503 (Core) What am I doing wrong? I need to be able to disable tcpv6 completely! Thanks Tim -- GPG me!! gpg --keyserver pool.sks-keyservers.net --recv-keys F186197B

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Discuss May 2015