CentOS is a free (as in beer and speech) GNU/Linux distribution that is community driven and based on source code released from RedHat.

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103
votes
17answers
125k views

CentOS vs. Ubuntu [closed]

I had a web server that ran Ubuntu, but the hard drive failed recently and everything was erased. I decided to try CentOS on the machine instead of Ubuntu, since it's based on Red Hat. That ...
78
votes
14answers
63k views

How do you install Node.JS on CentOS?

I've found numerous installation instructions for Node.js but they all seem so complicated -- I'm not a super sys admin but I can get around. I have yum on the system, but I didn't find any node.js ...
49
votes
9answers
59k views

When does `cron.daily` run?

When do entries in cron.daily (and .weekly and .hourly) run, and is it configurable? I haven't found a definitive answer to this, and am hoping there is one. I'm running RHEL5 and CentOS 4, but for ...
48
votes
2answers
6k views

Why is it so difficult to upgrade between major versions of Red Hat and CentOS?

"Can we upgrade our existing production EL5 servers to EL6?" A simple-sounding request from two customers with completely different environments prompted my usual best-practices answer of "yes, but ...
32
votes
5answers
23k views

“POSSIBLE BREAK-IN ATTEMPT!” in /var/log/secure — what does this mean?

I've got a CentOS 5.x box running on a VPS platform. My VPS host misinterpreted a support inquiry I had about connectivity and effectively flushed some iptables rules. This resulted in ssh listening ...
30
votes
4answers
10k views

Allow SFTP but disallow SSH?

I'm starting a very little hosting company for a few friends and little clients, nothing big. I want to give my "clients" the right to manage their files on the server. I hate FTP as it is not secure ...
29
votes
1answer
5k views

Why are my XFS filesystems suddenly consuming more space and full of sparse files?

I've run XFS filesystems as data/growth partitions for nearly 10 years across various Linux servers. I've noticed a strange phenomenon with recent CentOS/RHEL servers running version 6.2+. Stable ...
25
votes
4answers
61k views

Adding a directory to $PATH in CentOS?

We just got our new server(s) up and we're running CentOS on them all. After successfully installing Ruby Enterprise Edition, I would now like to add the REE /bin (located at ...
25
votes
3answers
7k views

The XFS filesystem is broken in RHEL/CentOS 6.x - What can I do about it?

Recent versions of RHEL/CentOS (EL6) brought some interesting changes to the XFS filesystem I've depended on heavily for over a decade. I spent part of last summer chasing down an XFS sparse file ...
24
votes
2answers
57k views

How do I configure LDAP on Centos 6 for user authentication in the most secure and correct way?

During the last couple of days I have been using a lot of F-words, while browsing Internet for good documentation about how to setup an LDAP-server. So far I have found none, but plenty that are less ...
23
votes
13answers
4k views

Linux IO monitoring per file?

I am interested in a utility or process for monitoring disk IO per file on CentOS. On Win2008, the resmon utility allows this type of drilldown, but none of the Linux utilities I have found do this ...
20
votes
4answers
74k views

How do I install an rpm that complains about rpmlib(FileDigests) <= 4.6.0-1?

Im trying to install an rpm file on CentOS 5 and Im not sure how to resolve this issues it brings up: $ rpm --install epel-release-6-5.noarch.rpm warning: epel-release-6-5.noarch.rpm: Header V3 ...
18
votes
12answers
76k views

How to find out details about hardware on the Linux machine?

-i.e - how to get a full list of hardware components in command line (on a machine with no window system) Thank you.
18
votes
12answers
21k views

Disable local delivery in Sendmail

I am using Sendmail on a Centos server to send email for PHP scripts, but the problem is that mail is delivered to a local mailbox on the machine rather than what is specified in the MX records for ...
17
votes
9answers
100k views

Check if port is open or closed on a Linux server using SSH?

How can I check if a port is open or closed on a Linux server (running Cent OS 5 and cPanel) using SSH? EDIT: And how can I open the port if it is closed? Thanks, James
17
votes
4answers
2k views

Monitoring production server

Hey all, We have 3 dedicated server, splitted in several VPS using openVZ. We're using munin to monitor the VPS with the production sites, and monit on some one of the VPS to make sure it restarts the ...
16
votes
14answers
1k views

Reasons for missing IP info in `last` output on pts logins?

I have five CentOS 6 linux systems at work, and encountered a rather strange issue that only seems to happen with my userid across all the linux systems I have... This is an example of the problem ...
16
votes
3answers
15k views

How can I get user name by user ID?

In my FTP client I can see files' owner ID (99). How do I find out which user is the owner of these files?
16
votes
2answers
263 views

Identification of physical network interface in linux [duplicate]

I'm new to linux and I have server with four network cards. I have to identify which physical network interface is assigned to the names eth0, eth1, eth2 and eth3. I have to disconnect cable from eth2 ...
15
votes
4answers
11k views

Failed to instal APC via pecl install APC

Hy when i try to install APC via pecl install APC-3.1.5 or even pecl install APC I get following error when the package comes to the make command: running: make /bin/sh ...
15
votes
3answers
27k views

How do I upgrade to the latest PHP version in CentOS with yum?

I found some blog posts about this, but it's rather lack of descriptions on possible side effects. I could really use some detailed on these steps: How to add a repo that provides PHP 5.4 into yum ...
14
votes
9answers
23k views

Easiest way for fast transfer of files between linux servers?

I need to transfer files from one CentOS server to another. Will transfer 5MB files about every 10 minutes. Do not need encryption. What is an easy was for fast transfer of files? Is there ...
14
votes
7answers
672 views

How to copy a previously entered command using the history utility without running it again?

I am able to use the history command on CentOS to get list of previous inputted commands, however, if I do something like: !372, history will attempt to run the referenced command. I need the ...
14
votes
3answers
13k views

How to install libpq-dev on Centos 5.5

In order to develop one web application based on postgresql, i need to install libpq on my centos. I can install it by "apt-get install libpq-dev" on ubuntu, but i can not install it on centos by ...
14
votes
4answers
18k views

Upgrade Subversion 1.6 to 1.7 on CentOS? (can't find yum repository)

I want to upgrade my SVN Server from 1.6 to 1.7. Unfortunately I can't find anything on the internet how to do this with yum. I have checked rpmforge-extras but it has only svn 1.6 and not 1.7 I ...
14
votes
2answers
28k views

Allowing FTP with IPTables

My current scenario involves allowing various rules, but I need ftp to be accessible from anywhere. The OS is Cent 5 and I am using VSFTPD. I can't seem to get the syntax correct. All other rules ...
14
votes
5answers
1k views

Unusually high dentry cache usage

Problem A CentOS machine with kernel 2.6.32 and 128 GB physical RAM ran into trouble a few days ago. The responsible system administrator tells me that the PHP-FPM application was not responding to ...
13
votes
8answers
15k views

How do I update a CentOS server's time from an authoritative time server?

I have CentOS machine and each time I've noticed that the server loses correct time after a while. It is usually behind by several minutes after time passes from having manually set the correct time. ...
13
votes
4answers
4k views

Improving IO with FlashCache

I have a server with 2 HDD's (2x 1 TB), running in RAID 1 (SW-RAID). I want to improve IO performance by using flashcache. There are running KVM virtual machines on it, using LVM. Regarding this, I ...
13
votes
2answers
486 views

What can be done to improve time synchronization on networks with sporadic internet access?

I'm looking for advice setting up time servers for a very non-typical network. I support many closed networks that have occasional access to the internet. A network would get access most days for a ...
13
votes
4answers
4k views

Managing an application across multiple servers, or PXE vs cfEngine/Chef/Puppet

We have an application that is running on a few (5 or so and will grow) boxes. The hardware is identical in all the machines, and ideally the software would be as well. I have been managing them by ...
12
votes
4answers
45k views

What is the value of JAVA_HOME for CentOS?

I have install java through yum on CentOS, however another java programme needs to know what the JAVA_HOME environmental variable is. I know all about setting environmental variables, but what do I ...
12
votes
5answers
31k views

where are the default ulimit values set? (linux, centos)

I have two CentOS (5) servers with nearly identical specs. When I login and do: ulimit -u on one machine, I get unlimited and on the other, 77824 When I run a cron like * * * * * ulimit ...
12
votes
1answer
1k views

Linux - if I change the hostname, which services need to be restarted?

I'm making some system hostname changes across a few environments and this got me thinking... When I change a server's hostname (live), what needs to be modified and which system services require a ...
12
votes
8answers
47k views

How do you re-mount an ext3 fs readwrite after it gets mounted readonly from a disk error?

Its a relatively common problem when something goes wrong in a SAN for ext3 to detect the disk write errors and remount the filesystem read-only. Thats all well and good, only when the SAN is fixed ...
12
votes
3answers
766 views

on Red Hat Enterprise and CentOS, what is creating /var/run/reboot-required?

On CentOS 5.8+ and Red Hat Enterprise 6+, when installing/updating packages, I notice a flag file /var/run/reboot-required is created when appropriate. On Ubuntu (and Debian too, I'm guessing), if ...
11
votes
6answers
8k views

How can I determine what is taking up so much space?

I was using df -h to print out human readable disk usage. I would like to figure out what is taking up so much space. For instance, is there a way to pipe this command so that it prints out files that ...
11
votes
3answers
763 views

/dev/null file became regular file

In our production server suddenly /dev/null became a regular file and due to this sshd service got stopped and not able to login the server. And also we tried to the below steps to configure back to ...
11
votes
3answers
10k views

My /var/log/btmp file is huge! What should I do?

My /var/log/btmp file is 1.3 GB in size. I've read that the file is "Used to store information about failed login". What does this mean for my server? And can i delete this file?
11
votes
5answers
1k views

Linux with 256GB of mem / 48 Cores - Machine starts thrashing/choking with tons of memory left

Machine: Dell r815, CentOS 5.4, 256GB of RAM, 4 x 12 Cores. We have an application that has a 275GB file. It does an in place sort on 20GB of data at a time i.e. it swaps bits around and replaces ...
11
votes
1answer
319 views

I have 23 Web Servers - I need to wipe all the servers - without loss of service on any sites hosted across them

Okay so it's a challenge and I'm having trouble planning it mostly due to lack of experience. However it's become a task in my job and I'm doing it mostly solo with an extra hand. I'm comfortable ...
11
votes
3answers
6k views

Installing Fedora RPMs in CentOS

How safe is it to install Fedora RPMs in CentOS 5? Does it depend on the version of the Fedora RPM or is it generally better to steer clear?
11
votes
4answers
15k views

How do I change timezone in centos 6.2?

Here is the output of my date command: [root@r1304 ~]# date Wed Apr 18 15:43:28 GST 2012 I want to change the default system timezone to Asia/Dubai. I've fallowed a tutorial and did fallowing: ln ...
11
votes
6answers
7k views

Automatically check for Security Updates on CentOS or Scientific Linux?

We have machines running RedHat-based distros such as CentOS or Scientific Linux. We want the systems to automatically notify us if there are any known vulnerabilities to the installed packages. ...
11
votes
5answers
4k views

Log all commands run by admins on production servers

It is company policy for admins to login to the servers via a personal username, and then run sudo -i to become root. Upon running sudo -i, sudo will create an environmental variable called ...
11
votes
6answers
6k views

Python 3.0 RPMs for CentOS 5 (RHEL 5)

Where is the best repository you use to obtain RPMs for Python 3.0 which are well maintained?
11
votes
1answer
2k views

CentOS thinks Disk is busy, can't mount or fsck

I'm a longtime user, and first time question submitter. I've spent a full day searching this and many other sites for a solution, but I must resort to requesting assistance to resolve my situation. ...
11
votes
2answers
379 views

bridge network between two linux servers

I need to set up following network architecture : Internet ^ +-----------------+ | +------------------+ | Centos6-1 | | ...
11
votes
2answers
1k views

Good practice for managing package updates for lots of CentOS servers

As part of my job I manage a few tens of CentOS 5 servers, using puppet for the main set up. About half of our servers have a standardised set up for hosting various django sites, while the rest are a ...
11
votes
3answers
4k views

SSD TRIM (discard) problems with ext4 on Crucial C300 SSDs with CentOS 5.5

Playing around with using a modern kernel (2.6.37 currently) on an older OS (CentOS 5.5) so we can get TRIM (discard) working on our SSDs (Crucial C300s). The most recent hdparm (9.37) concurs that ...