CentOS is an Enterprise-class Linux Distribution derived from Redhat Enterprise Linux sources freely provided to the public.

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43
votes
13answers
33k views

How can I get distribution name and version number in a simple shell script?

I'm working on a simple bash script that should be able to run on Ubuntu and CentOS distributions (support for Debian and Fedora/RHEL would be a plus) and I need to know the name and version of the ...
30
votes
6answers
41k views

Is CentOS exactly the same as RHEL?

I'm sure this question has been asked again and again elsewhere (I did not find anything specific to CentOS vs RHEL in SE), but I would still like to ask and confirm a few specific points. I am well ...
27
votes
7answers
1k views

What's the equivalent to && when writing a bash script?

I apologize in advance if this is a duplicate question. I did make an effort to search/check before asking here. I'm comfortable with writing one-liners like this: foocommand && ...
25
votes
2answers
44k views

CentOS 6 “Default” Installation Options

Can someone tell me the difference between a Desktop Install, a Basic Server install, and a Minimal Install? During installation, it doesn't give a description and I can't find documentation on it ...
16
votes
4answers
2k views

What makes CentOS “enterprisey” compared to “generic” distributions like Ubuntu?

What makes CentOS "enterprisey" compared to "generic" distributions like Ubuntu? When I say "enterprisey" I actually mean "better for server deployments". Just a general question, because I was ...
16
votes
2answers
10k views

How to colorize output of ls ?

I'm running CentOS in Linux text mode. When I run the command ls /usr/, the output is too hard to read (dark blue on black). How can I change the text coloring?
14
votes
7answers
4k views

Is there a difference of stability between Linux distros?

I've using Debian since 2010 for some home purposes and it has been stable. Is Debian still a good option if I need a server for heavy network, cpu, disk and memory usage? Last month I listened to ...
14
votes
9answers
43k views

Cannot enable network after CentOS 6.3 fresh install

I am trying to perform a fresh CentOS 6.3 installation then run various yum commands such as yum install httpd. The installation runs fine, however I cannot run any network based commands like yum I ...
11
votes
5answers
9k views

How can I limit the bandwidth used by a process?

I have a CentOS 5.7 server that will be backing up its files nightly. I am concerned that visitors to the various sites that the server hosts will experience degraded performance while the backup is ...
11
votes
10answers
52k views

How to install CentOS 6 via USB mass storage device?

I want to install CentOS 6.2 on a laptop (Thinkpad R40) which comes without CD/DVD-drive but with USB 2.0 ports. It seems that CentOS does not provide ready-to-use dd-able USB images for ...
10
votes
3answers
17k views

Why the default eth0 interface is down by default on CentOS?

I am already a little bit familiar with Linux distros like Debian or Ubuntu (yeah, very similar) but I wanted to try Red Hat based - CentOS 6.2 . I have installed it on my Windows 7 host in virtualBox ...
10
votes
2answers
233 views

Find out exact installation time of CentOS

I installed CentOS on my laptop about 8 month ago, and I want to know when exactly I installed it , how can I do that in CentOS 6.4 ?
10
votes
1answer
281 views

How can I monitor CPU usage by user?

I need to monitor CPU usage by users of two servers' (Ubuntu and CentOS). For example: user1 5% user2 10% ... Is there a tool similar to top or htop that can do that?
10
votes
1answer
7k views

BUG: soft lockup - CPU# stuck for x seconds

I've seen a few bug reports and questions (on stackexchange and elsewhere) regarding a nagging "BUG: soft lockup - CPU#<n> stuck for <dt>s!". So far, I haven't found any clue as to what ...
10
votes
3answers
765 views

Why are files in my home dir being created as world-writable despite a more-restrictive umask?

I've realized that the permissions for new files and directories behave a bit strangely. First of all, umask seems to return the right answer: $ umask 0002 This means full access for my user and ...
9
votes
1answer
550 views

How do you omit “./” when running scripts on current directory

On some tutorials over the internet they can run a script on the current directory without doing: ./script How do you omit this? I am using CentOS 5.6 x64. I want to run it this way script
9
votes
2answers
21k views

How to change the hostname of a linux machine using terminal?

I logged in for the first time, opened terminal, and typed in ‘hostname’. It returned ‘localhost.localdomain.com’. Then I logged as the root user in terminal using the command, ‘su –‘, provided the ...
9
votes
9answers
10k views

Package: git-1.7.6.1-1.el5.rf.i386 (rpmforge) Requires: libcurl.so.3

After I run yum install git it shows the error Error: Package: git-1.7.6.1-1.el5.rf.i386 (rpmforge) Requires: libcurl.so.3 You could try using --skip-broken to work around the problem You ...
8
votes
3answers
531 views

/bin /etc /lib64 /root /sbin deleted or moved by mv folder/* /* while su

OS is Centos 6.5 64-bit I downloaded a tar file and wanted to untar and mv it. I untared, then accidentally (as root) ran mv folder/* /* instead of mv folder/* . bash said it couldn't overwrite some ...
8
votes
4answers
18k views

“Symbolic link not allowed or link target not accessible” / Apache on CentOS 6

I've got a brand new CentOS 6 installation, which has a symlink in the document root to my development files: [root@localhost html]# ls -l total 4 -rwxrwxrwx. 1 root root 0 Sep 18 20:16 index.html ...
8
votes
2answers
4k views

CentOS: List the installed RPMs by date of installation/update?

I'm on a CentOS 4 machine. I updated and installed some packages a few weeks back, but I don't remember the name of every package or the names of every dependency. I used yum. Can I list the packages ...
8
votes
2answers
1k views

Should you run automatic updates

I'm running production Centos web servers. I want to know what is best practice for running updates. Should I automate this with yum-cron or yum-updatesd? Or is there a danger of updates breaking ...
8
votes
7answers
28k views

How can I fix “cannot find a valid baseurl for repo” errors on CentOS?

I finished installing CentOS 6, but when I tried running yum update I got: [root@centos6test ~]# yum update Loaded plugins: fastestmirror, refresh-packagekit Determining fastest mirrors Could not ...
8
votes
2answers
535 views

I Can't login as root with su command, but I can with SSH

How is it possible that I cannot log in as root by su root or su (I get incorrect password error), but I can log in by ssh root@localhost or ssh root@my_local_IP with the same password? I'm using ...
8
votes
2answers
7k views

Package bash-completion missing from Yum in CentOS 6

I am trying to get tab-completion working in Yum in CentOS 6 (so I can do something like yum install firefo<TAB> and get back firefox), and I have found many tutorials which say to simply do yum ...
8
votes
2answers
1k views

How can I disable TCP/IP for an Ethernet adapter?

I have CentOS 6.3 running in a (virtual) machine with two Ethernet adapters. I have eth0 connected to a TCP/IP LAN and eth1 connected to a DSL modem. The system is intended as a dedicated ...
8
votes
1answer
218 views

How are ACL permissions processed and in what order do they apply to a given user action?

CentOS 6.4 I'm trying to better understand how filesystem ACL rules are processed and in what order ACL rules apply. For example, let's say users bob and joe belong to a group called sales. Let's ...
8
votes
1answer
476 views

MySQL gets killed by OS every 25 days or so

About 4 months ago we migrated from MS SQL Server to MySQL 5.5. Since then we have been experiencing an issue once approximately ever 25 days since where CentOS runs out of memory and as a result it ...
8
votes
2answers
630 views

lsof - age of file

The *nix command lsof gives you a list of open files. Is anyone aware of a way that would also list how long a particular file has been open? Either by using lsof or any other command. I'm using ...
8
votes
3answers
408 views

Using real time kernel headers to compile userspace code vs default headers

Per customer requirements, I installed CentOS 5.6 with the default kernel. With this kernel installed, the time.h file includes the #define CLOCK_MONOTONIC. Now, a real-time kernel was installed ...
7
votes
3answers
442 views

How to remove a specific character in a string but only if there are no numbers in that line in Linux

I've been stumped with this seemingly simple-to-fix problem.. well, for a while. Here's example output from the file I need to edit: $cat file George Washington Geneva Convention 123,281,029 USD ...
7
votes
1answer
14k views

How To Install Virtualbox Guest Additions On CentOS via Command Line only

Reading the Virtualbox user manual, I finally got [here], which explains how to install Virtualbox Guest Additions on a Linux guest via Command Line. But it's not clear enough for me (I just started ...
7
votes
1answer
726 views

Why isn't the ls command listing huge filesizes?

In my Redhat Linux, I am getting the following error when executing the ls command. # ls ls: sugar.sql: Value too large for defined data type
7
votes
2answers
18k views

CentOS on HyperV - eth0 not in ifconfig?

I've launched a CentOS install in HyperV and assigned a NIC the same way I've done on an Ubuntu VM, however, the device simply isn't picked up. Only my loopback is found by ifconfig. How should I go ...
7
votes
2answers
4k views

How to configure network profiles in Centos?

I'm trying to setup two network profiles in Centos. One for at home, one for at work. The home profile has a fixed IP address, fixed gateway and DNS server addresses. The work profile depends on DHCP. ...
7
votes
3answers
783 views

Download ALL rpms for a product

I have two CentOS machines, one 6.3 box (A), and another CentOS 6.1. (B) 6.3 box is with internet connection, 6.1 box is without internet connection. I want to download ALL dependencies of a product ...
7
votes
0answers
2k views

OpenSSL Package Rebuild CentOS 6.4

Rebuilding openssl with Elliptic Curves on CentOS 6.4 The strategy is: 1) Download the "official" CentOS source package (.src.rpm) 2) Modify the .spec file to enable elliptic curves. (change no-EC ...
6
votes
4answers
973 views

What's the difference between a hard links and copied files?

RHEL 6 My understanding is that hard links include a copy of the original file and that I could delete a hard-linked file in one directory, and it would still exist in the other directory. If ...
6
votes
6answers
19k views

How to extend CentOS 5 partition on VMware?

I have a CentOS 5 virtual machine and I added 20GB more to disk size. How do I initialize and extend the available space? I'm new to Linux, so what should I do? I tried loading GParted as well, ...
6
votes
2answers
5k views

How can I know which IRQ is responsible of high CPU usage

I've moved a server from one mainboard to another due a disk controller failure. Since then I've noticed that constantly a 25% of one of the cores goes always to IRQ however I haven't managed myself ...
6
votes
2answers
4k views

In CentOS, what is the difference between yum update and yum upgrade?

What is the difference between yum update and yum upgrade, and when should I use one over the other?
6
votes
3answers
2k views

What does it mean to be in group 0?

Several users in a system I inherited have their group set to 0 in /etc/passwd. What does that mean? Do they essentially get full root privileges? The system is running CentOS 5, and the users ...
6
votes
2answers
346 views

Mysterious write IO

I am just reviewing the disk IO of a XEN VM server. I stumbled across a DomU that has constant write traffic. To narrow that traffic further down I logged in to the DomU (CentOS 5, 64 Bit) and ...
6
votes
3answers
3k views

How to execute a script on gdm login automatically for all users?

What file should I modify to execute some instructions when any user logs in through gdm? I tried /etc/bashrc but that is executed ony when starting bash (and each time an xterm is open). I'd like to ...
6
votes
3answers
6k views

What prevents a machine from responding to pings?

I have a CentOS release 5.4 linux box on Amazon EC2 that I'm trying to set up to be monitored via Nagios. The machine is in the same security group as the nagios server, but it seems to be ...
6
votes
2answers
1k views

Giving some users only SSH and shell access with limited resource usage

I'm trying to make a user that can access my server through SSH and allow it to have a shell, limited to using only, say screen and irssi. And it shouldn't it be able to see other directories except ...
6
votes
6answers
18k views

How do I upgrade OpenSSL?

According to these instructions: http://wiki.apache.org/httpd/NameBasedSSLVHostsWithSNI I need to use OpenSSL 0.9.8k or later (right now it's on 1.0.0c) to use name based virtual hosts in apache. ...
6
votes
4answers
1k views

Why do I need to hit enter to get my shell prompt after my init.d script completes?

I had to write my own CentOS init.d script for celery because it only ships with one for Debian. You can see the script I wrote when I answered my own stack overflow question 3989656. But there's a ...
6
votes
2answers
4k views

how do I install the stock centos repositories?

I have a situation where the stock repo files that should exist in /etc/yum.repos.d/ (like centos-base.repo) are not present. I need to get them installed. I am sure this is simple, but after hours of ...
6
votes
2answers
179 views

du command show a slash after directories?

How to use du command show a slash after directories? For example: du -ab /root/test/php-5.4.8/ Result: 1781 /root/test/php-5.4.8/main/internal_functions.c.in 973596 ...