Discuss January 2012

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222 participants
223 discussions

blue screen instead of login screen
by Frank Cox 14 Jan '12

14 Jan '12

I installed Centos 6.2/i386 on a machine last night with a 1920x1080 monitor. The installer ran in graphical mode and looked fine. After the install was finished I rebooted and ran through the "firstboot" stuff (set up user, etc) with no problem and, again, it looked good. After that, when I should have seen the gdm login screen, all I got was the blue background but not the box with the usernames in it, so there is no way to log in. "telinit 3", login to the text console, no problem. Type "startx", back to the same empty blue screen that gdm shows me. [root@ws194 log]# cat /etc/hosts 127.0.0.1 localhost localhost.localdomain ws194 ws194.ltsp ::1 localhost localhost.localdomain ws194 ws194.ltsp [root@ws194 log]# uname -a Linux ws194.ltsp 2.6.32-220.2.1.el6.i686 #1 SMP Thu Dec 22 18:50:52 GMT 2011 i686 i686 i386 GNU/Linux [root@ws194 log]# I rsynced /etc/skel to /home/myusername before running startx but that made no difference. Still got the blank blue screen. I tried disabling the Composite extension as directed here: http://www.linuxquestions.org/questions/slackware-14/unable-to-startx-after… Nothing changed. I don't see anything in /var/log/Xorg.0.log that looks too interesting; it appears that X figures it's running fine. This was working fine with a smaller monitor on Centos 5.7. Plus the Centos 6 installer looked fine, and the blue screen also looks nice and crisp, -- MELVILLE THEATRE ~ Real D 3D Digital Cinema ~ www.melvilletheatre.com www.creekfm.com - FIFTY THOUSAND WATTS of POW WOW POWER!

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Storage - posibilities?
by Rafał Radecki 14 Jan '12

14 Jan '12

Hi all. Currently I am administering a mail cluster in which messages are stored on software RAID shared with NFS. There are several NFS servers, every one of them exports a part of all mail files for a specific frontend with postfix. We are thinking about replacing these storage hosts with one solution, maybe a storage array with appropriate disk space and I/O capacity. What are pros and cons of that solution? Do storage arrays have appropriate I/O capacity (X*software RAID)? Does it scale good? Does storage capacity also scale good in those solutions? Best regards, R.

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iptable rule for bypassing netfilter queue for a matching address.‏
by Arif Tuhin 14 Jan '12

14 Jan '12

I have two iptable rules for userspace modification : iptable -t mangle -A PREROUTING -p udp --dport 9090 -j NFQUEUE iptable -t mangle -A OUTPUT -p udp --sport 9090 -j NFQUEUE I have the following network setup: client ---------------->Linux Box or router--------------------->server. What i'm trying to achieve is modifying all packets which comes from client to 9090 port of the Linux Box. Also which packets will go from Linux Box to client. I do not want to manipulate both from or to the server. So the rules i need will work like this: If packet comes from client to port 9090 i will modify it. Now the router opens symmetric port when it communicates with the server. That means it opens 9090 port when it communicates with the server and hence get modified by the second rule(--sport 9090). I want to avoid this. The rules will be like this: 1.If packet comes from a specific ip block i will accept it. then i will queue the remaining packets based on the destination port it comes to. 2.If packet goes to a specific ip block i will forward it. I will queue the remaining packets based on the source port information. Thanks in advance.

1 0

Rozważania odnośnie storage?
by Rafał Radecki 14 Jan '12

14 Jan '12

Cześć. Aktualnie mam do czynienia z klastrem pocztowym, w którym pliki wiadomości pocztowych użytkowników są przechowywane na raid software-owym udostępnianym po NFS. Serwerów NFS jest kilka, każdy udostępnia podzbiór wiadomości dla odpowiedniego serwera z postfix-em, który jest klientem NFS. Dane z jakiego serwera NFS host frontend z postfix-em powinien montować katalogi z pocztą są w MySQL. Zastanawiamy się nad zastąpieniem kilku host-ów storage jednym rozwiązaniem, macierzą o odpowiedniej pojemności dyskowej i wydajności I/O. Możecie podpowiedzieć plusy i minusy takiego rozwiązania? Czy macierze zazwyczaj dysponują kilkukrotnie większą wydajnością I/O niż pojedynczy serwer z dyskami SATA? Czy taka wydajność I/O jest skalowalna? Czy skalować przestrzeń dyskową w macierzach można "bez ograniczeń"? Dzięki! Pozdrawiam, R.

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defense-in-depth possible for sshd?
by Bennett Haselton 14 Jan '12

14 Jan '12

If an attacker finds an exploit to take control of httpd, they're still blocked in part by the fact that httpd runs as the unprivileged apache user and hence can't write any root-owned files on the system, unless the attacker also knows of a second attack that lets apache escalate its privilege. Basically correct? What about sshd -- assuming that the attacker can connect to sshd at all (i.e. not prevented by a firewall), if they find an exploit to let them take control of sshd, would that imply immediate total control of the machine? Because if they can control sshd they can tell sshd, "Allow root login (even if prohibited in sshd.conf) and accept 'foo' as the password", then the attacker can log in as root. Is it possible, even in theory, to provide a second layer of defense behind sshd to prevent the attacker from controlling the machine, if the attacker controls sshd? The "log me in as root" attack would appear to imply that an extra layer is not possible. (Note I'm not talking about extra layers of security *in front* of sshd, like a firewall that only permits logins from known locations. I'm also not talking about detection after the fact -- obviously you can detect unexpected root logins from the /var/log/secure* files if the attacker doesn't erase them -- only whether you could use extra layers to *prevent* the attacker from owning the machine if they take control of sshd.)

11 16

sendmail deferred
by Ismail Ozatay 13 Jan '12

13 Jan '12

Hi all, I having a problem with my sendmail server running on centos 5.7 x64. Sometimes when we send an email to microsoft exchange servers, sendmail says deferred or timeout. I do not know what is happening. Here is some details; [root@avgw ~]# sendmail -v -qRxxx(a)xxx.gov.qa Running /var/spool/mqueue/q0B7caw9023076 (sequence 1 of 2) <xxx(a)xxx.gov.qa>... Connecting to smtp.xxx.gov.qa. via esmtp... 220 mail.xxx.gov.qa Microsoft ESMTP MAIL Service ready at Fri, 13 Jan 2012 16:37:28 +0300 >>> EHLO avgw.yyy.com 250-mail.xxx.gov.qa Hello [95.9.x.x] 250-SIZE 10485760 250-PIPELINING 250-DSN 250-ENHANCEDSTATUSCODES 250-AUTH 250-8BITMIME 250-BINARYMIME 250 CHUNKING >>> MAIL From:<xxx(a)yyy.com> SIZE=939155 250 2.1.0 Sender OK >>> RCPT To:<xxx(a)xxx.gov.qa> >>> DATA 250 2.1.5 Recipient OK 354 Start mail input; end with <CRLF>.<CRLF> timeout writing message to smtp2.xxx.gov.qa.: Connection reset by smtp2.xxx.gov.qa. <xxx(a)xxx.gov.qa>... Deferred [root@avgw ~]# telnet smtp2.xxx.gov.qa 25 Trying 89.211.40.246... Connected to smtp2.xxx.gov.qa (89.211.x.x). Escape character is '^]'. 220 mail.xxx.gov.qa Microsoft ESMTP MAIL Service ready at Fri, 13 Jan 2012 17:54:56 +0300 It seems everything is ok but i do not know what is the problem with exchange communication. Has anybody experienced this issue? Regards

2 1

Is Amanda "vaulting" what I need for archiving data?
by Alan McKay 13 Jan '12

13 Jan '12

Hi folks, I've got a bit of a different scenario than I imagine most, and have spent the last 60 or 90 minutes searching Amanda list archives and googling, but did not come up with anything much. Then I went browsing around the Amanda website and found "vaulting" and was wondering whether this would suit my needs. I'm basically searching around for a backup solution and trying to decide whether to use something off the shelf or just roll my own with gtar. It is important to me that my solution use standard tools like dump/restore / gtar on the back end, which is how I ended up at Amanda. In looking through some of the initial configuration how-tos it seemed as though this was massively over-complex for my application. But then I hit upon "vaulting" http://wiki.zmanda.com/index.php/How_To:Copy_Data_from_Volume_to_Volume This is not exactly my scenario, but maybe there is another way to roll a "vaulting" solution to suit me. Basically I work in a scientific research lab (stem cell research) where the scientists produce a fair bit of raw data. We want to periodically take the data and archive it to tape and then remove it from disk and store the tape in our archival facility. We'd need a record of what is on each tape of course. But this would not be the same scenario as in the link above because it would not be taking data from 2ndary to tertiary storage. It would essentially be taken from primary to tertiary directly. i.e. directly from disk to tape. But not in an automated fashion like typical nightly dumps. On request, we'd take the scientist's data and copy it over to our server that has the tape unit, then dump it out to tape, and remove it from the disk there. Once verified, we could tell the scientist it is OK to remove their primary data now, and then we'd store the tape. Is Amanda suited to this? Or is there another application I should be looking at? thanks, -Alan -- “Don't eat anything you've ever seen advertised on TV” - Michael Pollan, author of "In Defense of Food"

5 6

A silly question about getting access to webapp installed with yum
by Rajagopal Swaminathan 13 Jan '12

13 Jan '12

Greetings, I have helped host a few applications such as GLPI, OCSInventory, etc etc. using the tarball method and untarring them in /var/www/htom directory. I have never done them though using yum. I was trying to install Trac, Bugzilla etc using yum install method on a Centos 6.2 box. Somehow I am not able to see the respective pages say even using http://localhost/trac or http://localhost/bugzilla Now comes the elementary and stupid question: Now where do these stuff get installed? they are not under /var/www/html I did find some under /usr/share Any pointers to instantiate them? I am not good at understanding what that beast of yum does as to post install script. Though I have created a mysql with CSV and blackhole engines about a year back and as I did it for a client of the company where I worked then and cannot have my grubby hands on that script. Any help appreciated. TIA -- Regards, Rajagopal

5 10

bug submission justified for distribution of obsolete java software?
by e-letter 13 Jan '12

13 Jan '12

Readers, Would someone advise whether the distribution of an obsolete version of java should be reported as a bug; http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=827

7 20

Re: [CentOS] USB install annoyances
by Darr247 13 Jan '12

13 Jan '12

> But this thread's gotten way OT: *does* anyone have any > idea what the .img file is that the running o/s from install.img > is looking for, after the partitioning, when it's ready to install? Possibly, but without the info I previously requested, I won't be trying to reproduce the problem. e.g. the source file[s] and command[s] used to make your bootable USB stick.

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Discuss January 2012