Strange characters appearing in CentOS login prompt

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Strange characters appearing in CentOS login prompt

Postby sumupeter » 2012/11/08 11:21:08

Hello CentOS Experts,

I have been running a CentOS 6.3 64 bit for about 6 months. This is my first CentOS installation - and my first linux installation too. I had some basic stuff installed on top of CentOS 6.3 minimal like Java, ssh, smb, tomcat, hudson, mysql & jira. I recently installed apache httpd and drupal.

I noticed something very strange when I booted the machine today. At the login name prompt, I saw the following characters being printed automatically - ^@^@^@^@^@^@. This was going on and on and whatever I was typing on the keyboard had no effect. I tried to reboot the machine and enter the boot menu but my keyboard input was not being accepted.

Though I am a bit worried that it's a virus or an OS crash, I think it could also be a problem with the wireless keyboard. I am going to check again by using a wired keyboard - instead of the Belkin wireless I use now - and I will post an update after that.

This is probably a very naive question for some of you experts but just wanted to know if anyone has come across anything like this.

Thank you,
Peter
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Strange characters appearing in CentOS login prompt

Postby TrevorH » 2012/11/08 13:34:17

Your keyboard had a stuck Ctrl key and was repeatedly sending the same character over and over. It happens sometimes, more often when using a KVM but I guess wireless keyboards could also suffer more than wired ones. It can usually be cured by pressing the offending key and releasing it - with the Ctrl key in this case you'd need to press both Ctrl keys to find out which one it was.
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Re: Strange characters appearing in CentOS login prompt

Postby sumupeter » 2012/11/08 16:55:13

Hi Trevor,

First of all thanks lot for responding - especially considering how simple the issue is especially for a Linux Admin like you.

I checked my keyboard and replaced it and the problem was resolved. What a relief:-) I was about to post an update and saw your reply. Thank you very much once again.

I also want to thank the entire CentOS team for such a nice and stable product. Being a newbie, I have had to read and use trial and error quite a bit but CentOS has been very stable and good so far. With this one issue, I was worried today and started checking RHEL license costs. I am grateful to all@CentOS that I don't have to go that route now:-)

I got a little paranoid because, I connect to my server over internet a lot and I have disabled selinux and disabled the firewall on some ports so the machine is accessible via port forwarding. As mentioned in my earlier post, I recently installed Drupal/PHP and having read somewhere that PHP has got security vulnerabilities - I know a hacker probably is going to gain nothing by hacking into my small server but if that happens a lot of my time/sweat would go waste - so was a bit concerned.

Having got over my inertia to ask in this forum, I would like to take this opportunity to ask the other question that I have always wanted to ask. What are the security precautions that someone using a set up like the one mentioned above should take. To summarize the environment:

1) selinux is disabled
2) port forwarding is used from modem to router to machine
3) firewall is disabled on ssh port, cvs(2401 I think), mysql(3306), samba, and some http ports(80XX and 90XX)

This is a different question so I can create a new topic if required.

Finally thanks again to Trevor and the entire CentOS team for such a well maintained and stable product. You guys are truly amazing.

regards,
Peter
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Re: Strange characters appearing in CentOS login prompt

Postby TrevorH » 2012/11/09 00:02:20

Look at the section in the Wiki about security http://wiki.centos.org/HowTos#head-ed80 ... d139e88421
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