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).

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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I am a new RHEL / Centos Linux server admin. I would like yum to update all packages except the Linux Kernel. How can I prevent yum command from updating kernel on a CentOS/RHEL/Fedora Linux based systems?

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I am a new CentOS / RHEL 6.x server user and DevOP. I need to lock a package called nginx on a server being updated via yum command. How do I lock package version at a particular version on CentOS / Red Hat Enterprise Linux (RHEL) 6.x or Fedora Linux?

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I am a new CentOS Linux user. How do I change default sshd tcp port # 22 to 2022 on CentOS Linux version 5/6?

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Is there is a tool that can provide me a maximum of information (such as cpu, disk I/O, network, nfsd, memory and more) about my Linux/Unix server in a minimum of space in a terminal?

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