CentOS Howtos and Tutorials

Centos Linux tutorial for beginners and advanced users with special focus on security, firewall, web, mail, file and proxy servers in an enterprise environment (rss feed).

My CentOS Linux based laptop can only be accessed through our corporate proxy servers. How do I access and use yum command with a Web proxy server on a CentOS / RHEL / Fedora / Red Hat / Scientific Linux?

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I am a new Linux server user. I need to tunnel X over ssh. I type the following command on a CentOS/RHEL based remote host to get display on a local desktop:

ssh -X user@server1.cyberciti.biz
xeyes &
firefox &

But, I am getting an error that read as follows:

**error**: Failed to contact configuration server; some possible causes are that you need to enable TCP/IP networking for ORBit, or you have stale NFS locks due to a system crash. See http://projects.gnome.org/gconf/ for information. (Details – 1: Failed to get connection to session: /bin/dbus-launch terminated abnormally without any error message)

How do I fix this error on a newly formatted/installed RHEL or CentOS Linux 6.x server?

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I recently read that SSH keys provide a secure way of logging into a Linux and Unix-based server. How do I set up SSH keys on a Linux or Unix based systems? In SSH for Linux/Unix, how do I set up public key authentication?

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I know how to install nginx on a CentOS Linux using yum command. Is there is a guide to install Lighttpd web-server on a CentOS Linux or RHEL server with yum command? How can I install and configure php and mysql on a CentOS with Lighttpd web-server?

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How do I install JDK runtime environment on a CentOS Linux version 6.x using yum command?

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I am using a CentOS Linux v6.5 on my home server and I am getting the following error when I execute yum command:

rpmdb: PANIC: fatal region error detected; run recovery
error: db3 error(-30974) from dbenv->open: DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db3 – (-30974)
error: cannot open Packages database in /var/lib/rpm
CRITICAL:yum.main:

Error: rpmdb open failed

How do I fix this problem on a CentOS / RHEL based system?

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I am using NFS server version 4.x on a CentOS/RHEL based system. I’m mounting my shared /var/www/ directory on five Apache based nodes using the following syntax:

mount -t nfs4 -o rw,intr,hard,proto=tcp rocknas02:/httproot/www /var/www/

I noticed that due to bug in my app user can sometime upload executable or other device files to get out of chrooted Apache server. How can I prevent such security issues on a CentOS or RHEL based NFS client and sever setup?

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