Frequently Asked Questions About Linux / UNIX » CentOS http://www.cyberciti.biz/faq Every answer asks a more beautiful question. Fri, 03 Feb 2012 22:38:32 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 CentOS / RHEL / Scientific Linux 6 Enable (Install) EPEL Repohttp://www.cyberciti.biz/faq/fedora-sl-centos-redhat6-enable-epel-repo/ http://www.cyberciti.biz/faq/fedora-sl-centos-redhat6-enable-epel-repo/#comments Tue, 24 Jan 2012 18:01:46 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11465 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?]]> http://www.cyberciti.biz/faq/fedora-sl-centos-redhat6-enable-epel-repo/feed/ 0 RHEL / CentOS 6 Linux Install Memcached High Performance Distributed Memory Object Cache Serverhttp://www.cyberciti.biz/faq/howto-install-memcached-under-rhel-fedora-centos/ http://www.cyberciti.biz/faq/howto-install-memcached-under-rhel-fedora-centos/#comments Tue, 24 Jan 2012 09:14:16 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11440 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?]]> http://www.cyberciti.biz/faq/howto-install-memcached-under-rhel-fedora-centos/feed/ 2 CentOS / RHEL: Change / Copy File SELinux Security Context Commandhttp://www.cyberciti.biz/faq/rhel-centos-feora-linux-change-copy-selinux-context/ http://www.cyberciti.biz/faq/rhel-centos-feora-linux-change-copy-selinux-context/#comments Wed, 28 Dec 2011 10:29:40 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11302 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?]]> http://www.cyberciti.biz/faq/rhel-centos-feora-linux-change-copy-selinux-context/feed/ 0 Linux: Neighbour Table Overflow Error and Solutionhttp://www.cyberciti.biz/faq/centos-redhat-debian-linux-neighbor-table-overflow/ http://www.cyberciti.biz/faq/centos-redhat-debian-linux-neighbor-table-overflow/#comments Mon, 19 Dec 2011 19:39:11 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11265 I setup a CentOS Linux based Linux server running as a gateway and firewall server. However, I'm getting the following messages in the /var/log/messages log file:
Dec 20 00:41:01 fw01 kernel: Neighbour table overflow. Dec 20 00:41:01 fw01 last message repeated 20 times
OR
Dec 20 00:41:01 fw03 kernel: [ 8987.821184] Neighbour table overflow. Dec 20 00:41:01 fw03 kernel: [ 8987.860465] printk: 100 messages suppressed.
Why does kernel throw "Neighbour table overflow" messages in syslog? How do I fix this problem under Debian / CentOS / RHEL / Fedora / Ubuntu Linux?]]> http://www.cyberciti.biz/faq/centos-redhat-debian-linux-neighbor-table-overflow/feed/ 0 CentOS / RHEL: Remove Routes 169.254.0.0 / 255.255.0.0 From the Systemhttp://www.cyberciti.biz/faq/fedora-centos-rhel-linux-disable-zeroconf-route-169-254-0-0/ http://www.cyberciti.biz/faq/fedora-centos-rhel-linux-disable-zeroconf-route-169-254-0-0/#comments Fri, 04 Nov 2011 23:29:33 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11178 How do I disable the route 169.254.0.0 / 255.255.0.0 from CentOS or RHEL 6 Linux server?]]> http://www.cyberciti.biz/faq/fedora-centos-rhel-linux-disable-zeroconf-route-169-254-0-0/feed/ 6 memcached: Failed To Set rlimit For Open Files Error and Solutionhttp://www.cyberciti.biz/faq/linux-unix-rhel-centos-memcache-failedto-setrlimit/ http://www.cyberciti.biz/faq/linux-unix-rhel-centos-memcache-failedto-setrlimit/#comments Tue, 11 Oct 2011 18:36:21 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11153 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?]]> http://www.cyberciti.biz/faq/linux-unix-rhel-centos-memcache-failedto-setrlimit/feed/ 2 RHEL / CentOS Linux: Mount and Access NTFS Partitionhttp://www.cyberciti.biz/faq/redhat-fedora-enable-ntfs3g-support/ http://www.cyberciti.biz/faq/redhat-fedora-enable-ntfs3g-support/#comments Mon, 05 Sep 2011 05:47:11 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10997 How to enable NTFS support on CentOS Linux version 5 or 6? How do I mount ntfs partition under RHEL 5 or 6?]]> http://www.cyberciti.biz/faq/redhat-fedora-enable-ntfs3g-support/feed/ 9 CentOS / RHEL: Install gpass Password Manager For GNOME2 Desktophttp://www.cyberciti.biz/faq/redhat-scientific-fedora-install-gpass-rpm-yum-command/ http://www.cyberciti.biz/faq/redhat-scientific-fedora-install-gpass-rpm-yum-command/#comments Fri, 26 Aug 2011 11:59:33 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10955 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?]]> http://www.cyberciti.biz/faq/redhat-scientific-fedora-install-gpass-rpm-yum-command/feed/ 0 RHEL 6 / CentOS 6: Install Adobe Flash Player For Firefox Browserhttp://www.cyberciti.biz/faq/redhat-linux-yum-install-flash-player-for-firefox/ http://www.cyberciti.biz/faq/redhat-linux-yum-install-flash-player-for-firefox/#comments Wed, 24 Aug 2011 21:21:57 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10926 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?]]> http://www.cyberciti.biz/faq/redhat-linux-yum-install-flash-player-for-firefox/feed/ 4 yum Command Hangs on Running Transaction Test Message Error and Solutionhttp://www.cyberciti.biz/faq/rhel-centos-fedora-redhat-yum-running-transaction-test-error/ http://www.cyberciti.biz/faq/rhel-centos-fedora-redhat-yum-running-transaction-test-error/#comments Fri, 01 Jul 2011 23:53:45 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10778 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?]]> http://www.cyberciti.biz/faq/rhel-centos-fedora-redhat-yum-running-transaction-test-error/feed/ 2 Linux Syslogd: Nothing Gets Logged Using /dev/log And /jail/apache/dev/loghttp://www.cyberciti.biz/faq/syslog-fails-to-open-devlog-nothing-gets-logged/ http://www.cyberciti.biz/faq/syslog-fails-to-open-devlog-nothing-gets-logged/#comments Sun, 22 Aug 2010 07:33:19 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8636 I've configured my Apache in chrooted jail at /jail/apache directory. However, my syslogd is not working and nothing gets logged using /dev/log and /jail/apache/dev/log. How do I fix this problem under CentOS 5.x AMD64 with SELinux?]]> http://www.cyberciti.biz/faq/syslog-fails-to-open-devlog-nothing-gets-logged/feed/ 0 Linux KVM: OpenBSD Guest Hangs At Starting tty Flagshttp://www.cyberciti.biz/faq/kvm-virtualization-openbsd-guest-hangs-at-starting-tty-flags/ http://www.cyberciti.biz/faq/kvm-virtualization-openbsd-guest-hangs-at-starting-tty-flags/#comments Thu, 15 Jul 2010 20:25:49 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8337 OpenBSD version 4.5 and above made changes in kernel which prevents booting OpenBSD using KVM technology. OpenBSD 4.4 runs with mbbios enabled. However, due to some sort of bug in KVM it does not boots. The workaround is to disable mpbios. This may or may not happen with your installation. ]]> http://www.cyberciti.biz/faq/kvm-virtualization-openbsd-guest-hangs-at-starting-tty-flags/feed/ 0 KVM virt-install: Install OpenBSD As Guest Operating Systemhttp://www.cyberciti.biz/faq/kvmvirtualization-virt-install-openbsd-unix-guest/ http://www.cyberciti.biz/faq/kvmvirtualization-virt-install-openbsd-unix-guest/#comments Thu, 15 Jul 2010 19:36:26 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8314 OpenBSD is a UNIX like system based on Berkeley Software Distribution (BSD). It was forked form NetBSD and created by Theo de Raadt in 1995. OpenBSD is famous for quality code and documentation without compromising position on software licensing. OpenBSD is also well know for focus on security features such as Memory protection, cryptography, randomization and much more in default base installation. ]]> http://www.cyberciti.biz/faq/kvmvirtualization-virt-install-openbsd-unix-guest/feed/ 0 KVM: Start a Virtual Machine / Guest At Boot Timehttp://www.cyberciti.biz/faq/rhel-centos-linux-kvm-virtualization-start-virtual-machine-guest/ http://www.cyberciti.biz/faq/rhel-centos-linux-kvm-virtualization-start-virtual-machine-guest/#comments Wed, 14 Jul 2010 19:30:58 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8296 There are various ways to start virtual machines at at boot time. This means you don't have to type virsh start vmName command. This can be done by marking a vm as autostart. ]]> http://www.cyberciti.biz/faq/rhel-centos-linux-kvm-virtualization-start-virtual-machine-guest/feed/ 0 CentOS / Redhat Linux: Install OpenNTPD To Synchronize The Local Clockhttp://www.cyberciti.biz/faq/openntpd-on-centos-rhel-fedora-linux/ http://www.cyberciti.biz/faq/openntpd-on-centos-rhel-fedora-linux/#comments Thu, 24 Jun 2010 02:02:21 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=7953 OpenNTPD is a Unix system daemon implementing the Network Time Protocol to synchronize the local clock of a computer system with remote NTP servers. How do I install OpenNTPD under CentOS / RHEL / Fedora Linux instead of default NTPD client / server?]]> http://www.cyberciti.biz/faq/openntpd-on-centos-rhel-fedora-linux/feed/ 0 Redhat Linux Network Interface Configuration (NIC) File Locationhttp://www.cyberciti.biz/faq/where-are-nic-files-located-in-redhat-fedora-centos-linux/ http://www.cyberciti.biz/faq/where-are-nic-files-located-in-redhat-fedora-centos-linux/#comments Sat, 19 Jun 2010 21:21:11 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=9785 Where are NIC (network interface configuration) files located in the Redhat / Fedora / Centos Linux? ]]> http://www.cyberciti.biz/faq/where-are-nic-files-located-in-redhat-fedora-centos-linux/feed/ 0 Linux KVM: Disable virbr0 NAT Interfacehttp://www.cyberciti.biz/faq/linux-kvm-disable-virbr0-nat-interface/ http://www.cyberciti.biz/faq/linux-kvm-disable-virbr0-nat-interface/#comments Wed, 16 Jun 2010 09:26:12 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=7886 The virtual network (virbr0) used for Network address translation (NAT) which allows guests to access to network services. However, NAT slows down things and only recommended for desktop installations. To disable Network address translation (NAT) forwarding type the following commands:]]> http://www.cyberciti.biz/faq/linux-kvm-disable-virbr0-nat-interface/feed/ 8 CentOS / Redhat: Install KVM Virtualization Softwarehttp://www.cyberciti.biz/faq/centos-rhel-linux-kvm-virtulization-tutorial/ http://www.cyberciti.biz/faq/centos-rhel-linux-kvm-virtulization-tutorial/#comments Sat, 12 Jun 2010 10:46:29 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=7628 KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions Intel VT or AMD-V. How do I install KVM under CentOS or Red Hat Enterprise Linux version 5.5?

This FAQ entry is part 1 of 7 in the series Redhat KVM Virtulization:

]]> http://www.cyberciti.biz/faq/centos-rhel-linux-kvm-virtulization-tutorial/feed/ 24 CentOS / Redhat: Setup NFS v4.0 File Serverhttp://www.cyberciti.biz/faq/centos-fedora-rhel-nfs-v4-configuration/ http://www.cyberciti.biz/faq/centos-fedora-rhel-nfs-v4-configuration/#comments Wed, 02 Jun 2010 21:09:06 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=7590 How do I setup NFS v4.0 distributed file system access server under CentOS / RHEL v5.x for sharing files with UNIX and Linux workstations? How to export a directory with NFSv4? How to mount a directory with NFSv4?]]> http://www.cyberciti.biz/faq/centos-fedora-rhel-nfs-v4-configuration/feed/ 12 CentOS / Redhat: Create Software RAID 1 Arrayhttp://www.cyberciti.biz/faq/centos-redhat-rhel-linux-setup-create-raid1/ http://www.cyberciti.biz/faq/centos-redhat-rhel-linux-setup-create-raid1/#comments Wed, 26 May 2010 07:41:29 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=7521 Recently, I've added another 73GB SAS disk to my Linux server after the installation. I've 30GB empty partition on old hard disk. How do I convert old /dev/sda3 and new /dev/sdb1 (both 30GB) into RAID 1 to improve NFS server speed and reliability?]]> http://www.cyberciti.biz/faq/centos-redhat-rhel-linux-setup-create-raid1/feed/ 9