Frequently Asked Questions About Linux / UNIX » RedHat and Friends

HowTo: Flush Contents Of a Memcached Server Using Command Line

Vivek Gite — Sat, 28 Jan 2012 00:35:21 +0000

I've installed memcached server under Linux but it is still showing old data. How do I flush the contents of a Memcached instance / server?

CentOS / RHEL / Scientific Linux 6 Enable (Install) EPEL Repo

Vivek Gite — Tue, 24 Jan 2012 18:01:46 +0000

Extra Packages for Enterprise Linux (or EPEL) is a Fedora Special Interest Group that creates, maintains, and manages a high quality set of additional packages for Enterprise Linux, including, but not limited to, Red Hat Enterprise Linux (RHEL),CentOS and Scientific Linux (SL). How do I enable it under CentOS 6 or RHLE 6 server?

RHEL / CentOS 6 Linux Install Memcached High Performance Distributed Memory Object Cache Server

Vivek Gite — Tue, 24 Jan 2012 09:14:16 +0000

How do I install memcached server under Red Hat Enterprise Linux 6.x server running on IBM hardware to cache query for my php based apps?

CentOS / RHEL: yum Command Reinstall Package

Vivek Gite — Fri, 30 Dec 2011 11:05:21 +0000

I accidental deleted the configuration file stored in /etc/ directory and the latest backup were made yesterday. How do I resinstall the package using the yum command under RHEL / CentOS Linux server?

CentOS / RHEL: Change / Copy File SELinux Security Context Command

Vivek Gite — Wed, 28 Dec 2011 10:29:40 +0000

I've created a file as follows:

ls -l -Z /etc/cron.d/vnstat -rw-r--r--. root root system_u:object_r:system_cron_spool_t:s0 /etc/cron.d/vnstat

I've created a new file /etc/cron.d/vnstat.custom.interface:

ls -l -Z /etc/cron.d/vnstat.custom.interface -rw-r--r--. root root unconfined_u:object_r:system_cron_spool_t:s0 /etc/cron.d/vnstat.custom.interface

The /etc/cron.d/vnstat is part of default vnstat package. I've installed my own version of the same. But, due to SELinux security cron job is not running. How do I change file SELinux security contex under RHEL / CentOS 6 Linux server to system_u:object_r:system_cron_spool_t:s0 from unconfined_u:object_r:system_cron_spool_t:s0 for /etc/cron.d/vnstat.custom.interface file?

RHEL / CentOS Yum Command: Blacklist Packages [ Disable Certain Packages ]

Vivek Gite — Wed, 28 Dec 2011 09:26:14 +0000

How do I force yum command to disable certain packages from being installed using certain repos such as EPEL under RHEL or CentOS Linux 6.x server?

CentOS / RHEL: Remove Routes 169.254.0.0 / 255.255.0.0 From the System

Vivek Gite — Fri, 04 Nov 2011 23:29:33 +0000

How do I disable the route 169.254.0.0 / 255.255.0.0 from CentOS or RHEL 6 Linux server?

Linux: Reset High Speed USB Device Using ehci_hcd Error and Solution

Vivek Gite — Thu, 13 Oct 2011 22:35:21 +0000

I've recently installed CentOS / RHEL 6.x on the server. I'm getting the following messages in /var/log/messages file logged frequently :

Oct 13 14:00:20 server1 kernel: usb 1-7: reset high speed USB device using ehci_hcd and address 2 Oct 13 14:05:57 server1 kernel: usb 1-7: reset high speed USB device using ehci_hcd and address 2 Oct 13 14:09:18 server1 kernel: usb 1-7: reset high speed USB device using ehci_hcd and address 2 Oct 13 14:11:42 server1 kernel: usb 1-7: reset high speed USB device using ehci_hcd and address 2 Oct 13 14:11:49 server1 kernel: usb 1-7: reset high speed USB device using ehci_hcd and address 2

How do I solve this problem?

memcached: Failed To Set rlimit For Open Files Error and Solution

Vivek Gite — Tue, 11 Oct 2011 18:36:21 +0000

I'm using RHEL 6 / CentOS 6.x and install the memcached server. However, whey I try to start the server using service memcached start command, I get the following error:

Starting memcached: failed to set rlimit for open files. Try running as root or requesting smaller maxconns value. [FAILED]

How do I fix this problem?

RHEL / CentOS Linux: Mount and Access NTFS Partition

Vivek Gite — Mon, 05 Sep 2011 05:47:11 +0000

How to enable NTFS support on CentOS Linux version 5 or 6? How do I mount ntfs partition under RHEL 5 or 6?

CentOS / RHEL: Install gpass Password Manager For GNOME2 Desktop

Vivek Gite — Fri, 26 Aug 2011 11:59:33 +0000

I've recently swiched from Ubuntu Linux to CentOS / RHEL version 6 gnome desktop. However, I'm unable to find the gpass the password manager for GNOME2 desktop in repo. How do I install the same under RHEL 6 or CentOS or Scientific Linux 6 or Fedora Linux 15?

RHEL 6 / CentOS 6: Install Adobe Flash Player For Firefox Browser

Vivek Gite — Wed, 24 Aug 2011 21:21:57 +0000

U'm using RHEL 6.x workstation with Mozilla Firefox 3.x. How do I install flash player so that I can use video site such as You-tube under RHEL 6.x or CentOS Linux 6.x 64bit operating systems?

rpmbuild: error: Installed (but unpackaged) file(s) found Solution

Vivek Gite — Mon, 22 Aug 2011 21:32:44 +0000

I'm trying to build a RHEL 6 rpm of nginx server. But, I get the following error:

+ /usr/lib/rpm/brp-strip-comment-note Checking for unpackaged file(s): /usr/lib/rpm/check-files /root/rpmbuild/BUILDROOT/nginx-1.0.5-1.el6.x86_64 error: Installed (but unpackaged) file(s) found: /usr/local/nginx/conf/fastcgi.conf /usr/local/nginx/conf/fastcgi.conf.default ... .... . /usr/local/nginx/html/50x.html /usr/local/nginx/html/index.html /usr/local/nginx/sbin/nginx RPM build errors: Installed (but unpackaged) file(s) found: /usr/local/nginx/conf/fastcgi.conf /usr/local/nginx/conf/fastcgi.conf.default ... .. . /usr/local/nginx/html/50x.html /usr/local/nginx/html/index.html /usr/local/nginx/sbin/nginx

How do I fix this problem and build rpm file?

CentOS / RHEL: Delete Old Yum Repositories and Configuration Files

Vivek Gite — Fri, 15 Jul 2011 10:26:08 +0000

How do I delete old yum repositories and configuration files under RHEL 5 or CentOS Linux server?

Slow DNS on Linux with IPv4 and IPV6 Configured Firewall

Vivek Gite — Mon, 04 Jul 2011 05:23:11 +0000

I'm getting slow DNS response from ssh and other network related traffic with delay of 30-60+ seconds per connection. All of our servers are behind hardware based dedicated firewall. My RHEL v6.1 server system running on HP hardware. How do I fix this problem?

yum Command Hangs on Running Transaction Test Message Error and Solution

Vivek Gite — Fri, 01 Jul 2011 23:53:45 +0000

When I run 'yum install package' or 'yum update' commands the yum command works normally until Running Transaction Test and hangs until the yum process is killed manually using the kill command. How do I fix this problem under CentOS Linux 5.x AMD64 running on HP server?

RHEL Warning: RPMDB altered outside of yum

Vivek Gite — Tue, 14 Jun 2011 20:06:54 +0000

When I try to update my server using the yum command I've been seeing the following error / warning message:

yum install aide
Loaded plugins: rhnplugin
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package aide.x86_64 0:0.14-3.el6 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
=============================================================================================================================================================================================
 Package                                Arch                                     Version                                        Repository                                              Size
=============================================================================================================================================================================================
Installing:
 aide                                   x86_64                                   0.14-3.el6                                     rhel-x86_64-server-6                                   123 k
Transaction Summary
=============================================================================================================================================================================================
Install       1 Package(s)
Total download size: 123 k
Installed size: 0
Is this ok [y/N]:
Downloading Packages:
aide-0.14-3.el6.x86_64.rpm                                                                                                                                            | 123 kB     00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
  Installing : aide-0.14-3.el6.x86_64                                                                                                                                                    1/1
Installed:
  aide.x86_64 0:0.14-3.el6

How do I fix this problem?

RHEL / CentOS / Fedora: Verify GPG Key For Package Update

Vivek Gite — Tue, 14 Jun 2011 19:46:04 +0000

How do I verify that the system using correct GPG keys to verify all patches, packages and update installed from RHN or repo under RHEL 5 or 6 server operating systems?

Linux /boot: Out of Disk Space While Installing Package kernel-2.6.32-131.2.1.el6.x86_64

Vivek Gite — Wed, 08 Jun 2011 12:02:10 +0000

I'm trying to install RHEL 6 kernel updates and patches using the yum command and getting the following error:

Transaction Check Error:
  installing package kernel-2.6.32-131.2.1.el6.x86_64 needs 8MB on the /boot filesystem
Error Summary
-------------
Disk Requirements:
  At least 8MB more space needed on the /boot filesystem.

How do I fix this error and install RHEL kernel without increasing /boot size or reinstalling the operating system?

HowTo: Find Out RHEL 6 / CentOS 6 Kernel Version

Vivek Gite — Mon, 06 Jun 2011 19:56:49 +0000

How do I find out my RHEL (Red Hat Enterprise Linux) 6 Linux kernel version number running on HP server?