Ubuntu Linux is a Debian derivative that aims to bring Linux mainstream. Questions on this site should generally refer to Ubuntu Server. Note that http://askubuntu.com is specifically dedicated to Ubuntu questions.

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103
votes
17answers
126k 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 ...
72
votes
7answers
26k views

Heartbleed: how to reliably and portably check the OpenSSL version?

I was looking at a reliable and portable way to check the OpenSSL version on GNU/Linux and other systems, so users can easily discover if they should upgrade their SSL because of the Heartbleed bug. ...
60
votes
11answers
61k views

apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName

I keep getting this warning when I (re)start Apache. * Restarting web server apache2 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ...
50
votes
5answers
3k views

How should an IT department choose a Linux distribution: Technical reasons

There is a lot of community feeling about what Linux distributions are appropriate for production server environments and what aren't. Some of this is based on the availability of commercial support. ...
47
votes
7answers
58k views

How to determine JAVA_HOME on Debian/Ubuntu?

On Ubuntu it is possible to have multiple JVMs at the same time. The default one is selected with update-alternatives. But this does not set the JAVA_HOME environment variable, due to a debian policy. ...
43
votes
10answers
166k views

How to start/stop iptables on Ubuntu?

How can I start/stop the iptables service on Ubuntu? I have tried service iptables stop but it is giving "unrecognized service". Why is it doing so? Is there any other method?
38
votes
5answers
3k views

How do I empty /dev/null? [closed]

I am using Ubuntu 10.10. I am generally good with computers but mostly with Windows, I'm not very familiar with Ubuntu. I'm trying to setup a website and I'm talking with a friend I have who works ...
35
votes
5answers
11k views

How does Ubuntu keep track of the “System restart required” flag in motd?

I have a few Ubuntu servers (8.10, 9.10) that is set to automatically install security updates. Some times these updates requires a restart of the system, and this string is shown in motd: *** System ...
35
votes
10answers
12k views

Securing a fresh Ubuntu server [closed]

Say I've got a fresh install of Ubuntu, what steps should I take to secure it for use as a Rails application server?
35
votes
4answers
14k views

Why don't EC2 ubuntu images have swap?

I started a couple servers on EC2 and they don't have swap. Am I doing something wrong or is it that the machines just don't have any?
34
votes
3answers
8k views

How to remove the “installed manually” flag and revert to “automatically installed” with apt-get?

To compile something, I needed the zlib1g-dev package to be installed so I launched an apt-get install zlib1g-dev. apt-get informed me nicely that the package was already auto-installed because of ...
34
votes
3answers
9k views

.profile vs. .bash_profile vs. .bashrc

what are the functional differences between these guys?
33
votes
6answers
20k views

How do I permanently disable Linux's console screen saver, system-wide?

I've got an Ubuntu server that boots up in text mode. It rarely has a screen or keyboard attached to it, but when I do attach a screen, I usually have to attach a keyboard too, because the darn ...
30
votes
4answers
24k views

How do you use apt-get to only install critical security updates on ubuntu?

How do you use apt-get to only install critical security updates on ubuntu? We'd like to only upgrade packages that need to be upgraded for security reasons, without upgrading all other packages.
29
votes
4answers
46k views

how do I upgrade from php 5.3 to php 5.4.6 in ubuntu?

Is there an easy way out to get the latest PHP? I have tried updating my package but none of it has 5.4.6 yet.. if anyone knows on how to do it quickly, can it be shared here? I've tried compiling ...
28
votes
7answers
29k views

What is the debian-sys-maint MySQL user (and more)?

I have been bitten several times by the 'debian-sys-maint' user that is installed by default on the mysql-server packages installed from the Ubuntu repositories. Generally what happens is I pull a ...
28
votes
4answers
18k views

ubuntu apache: httpd.conf or apache2.conf?

which one of these 2 files should i use to configure apache? the httpd.conf is empty while apache2.conf is not. it confuses me!
26
votes
14answers
12k views

File Server - Storage configuration: RAID vs LVM vs ZFS something else…?

We are a small company that does video editing, among other things, and need a place to keep backup copies of large media files and make it easy to share them. I've got a box set up with Ubuntu ...
26
votes
7answers
16k views

Headless Ubuntu server machine sometimes stuck at GRUB menu

I have Ubuntu 10.10 Server installed on a single-board machine in a semi-embedded environment; no keyboard or screen, just SSH access to it. So it's really frustrating when it occasionally boots up ...
26
votes
4answers
33k views

Setup ubuntu server to send mail()

I tried searching a lot but unable to find how to actually setup a ubuntu server, so that I can send mails through php using mail() function in php. I have apache2, mysql and php5 installed on my ...
25
votes
8answers
17k views

My server is still vulnerable to heartbleed even after I update OpenSSL

I have an Ubuntu 12.04 server. I have updated the OpenSSL package in order to fix the heartbleed vulnerability. But I am still vulnerable even, even though I have restarted the web server, and even ...
24
votes
7answers
39k views

How to get e-mail from (failed) cron-jobs in Ubuntu?

I create cron-jobs in Ubuntu by placing the executable in one of /etc/cron.{daily,hourly,monthly,weekly}. There are lots of directories starting with cron: kent@rat:~$ ls -ld /etc/cron* drwxr-xr-x 2 ...
24
votes
7answers
2k views

Ubuntu, how to setup a new machine like an existing one

I have one machine setup with the apps I need, and I'd like to install the same on a new Ubuntu box. Is there a script that will list all the installed apps, so that I can diff between the boxes and ...
24
votes
7answers
16k views

Why rsync is faster than NFS?

Few days ago I noticed something rather odd (at least for me). I ran rsync copying the same data and deleting it afterwards to NFS mount, called /nfs_mount/TEST. This /nfs_mount/TEST is ...
23
votes
9answers
10k views

Are configuration management tools (Puppet, Chef) capable of keeping installed packages up to date?

This is probably a simple question for those of you already running configuration management tools. Are configuration management tools such as Puppet or Chef the right approach for keeping installed ...
23
votes
9answers
37k views

How do I get apt-get to ignore some dependencies?

How do I make apt-get ignore some dependencies? For example, I wanted to install mailx so I can use it to send email from cron scripts/report-generating tools. However, installing mailx also installs ...
23
votes
7answers
15k views

Unzipping files that are flying in through a pipe

Can I make unzip or any similar programs work on the standard output? The situation is I'm downloading a zip file, which is supposed to be unzipped on the fly. Related issue: ...
22
votes
9answers
48k views

How do I find out whether a port is available on Ubuntu 8.04?

Is there any command I can run from bash that will tell me whether a port is already open?
22
votes
8answers
4k views

accidently ran “chown www-data:www-data / -R” as root

i just ran this a few seconds ago, i managed to do ctrl-c as soon as i realized what i started doing. so far in the only dir its started going through is /bin im afraid to do anything else, so far ...
22
votes
4answers
70k views

Where to set java heap options (e.g. -Xmx) for Tomcat 6 under Ubuntu 9.04?

I'm running Tomcat using the tomcat6 package from Ubuntu 9.04, which makes a daemon out of Tomcat using jsvc. I'd like to know the proper way to set Java heap options like -Xmx for Tomcat. I'd like to ...
22
votes
2answers
10k views

Can someone clarify Ubuntu (Debian) dist-upgrade for me?

I've got an Ubuntu 8.04 LTS server. There are several packages which are "kept back" ("the following updates have been kept back:") when I do an apt-get upgrade. It's my understanding that I can do ...
22
votes
3answers
15k views

Testing whether jumbo frames are actually working

Is there a command to test whether jumbo frames are actually working? i.e. some sort of "ping" that reports whether or not the packet was broken up along the way. I've an ESXi host with an Ubuntu VM ...
22
votes
7answers
31k views

How to set up Mod_WSGI for Python on Ubuntu

I am trying to setup MOD_WSGI on my Ubuntu box. I have found steps that said I needed to do the following steps I found at http://ubuntuforums.org/showthread.php?t=833766 sudo apt-get install ...
21
votes
6answers
78k views

add new user with root access in Linux

I want to add new user and have/grant that new user to have all the root access, how can I do that ? I did sudo adduser --system testuser but this is not working as I expected. Thanks for help.
20
votes
5answers
3k views

A domain I've never heard of resolves to my website [duplicate]

I've discovered (via looking at mod_pagespeed cache entries) that a completely random domain I've never heard of before is resolving to my website. If I visit this domain, my website loads. The DNS ...
20
votes
1answer
6k views

How do I ask apt-get to skip any interactive post-install configuration steps?

I have a server build script which uses apt-get to install packages. It then puts pre-written configuration files directly in place, so the interactive post-install configuration dialog in packages ...
20
votes
6answers
8k views

Verify TRIM support with BtrFS on SSD

We are looking into using BtrFS on an array of SSD disks and I have been asked to verify that BtrFS does in fact perform TRIM operations upon deleting a file. So far I have been unable to verify that ...
19
votes
8answers
13k views

Calculate MD5 checksum of a directory

I'm looking for a quick way to compare directory contents. Is it possible to do an md5sum (or equivalent checksum) of an entire directory? Using Ubuntu Linux
19
votes
6answers
10k views

Scripted install of MySQL on Ubuntu

I need to write a script that will build my server from a fresh Ubuntu server install. Among things like Apache and PHP it needs to install MySQL. The only problem here is that when I install MySQL ...
19
votes
6answers
16k views

Amazon Linux vs. Ubuntu for Amazon EC2

I'm setting up my first website on Amazon EC2, and I'm trying to decide which distro to use. I've used Redhat and CentOS in the past, but I have no bias towards any system, I just want to use whatever ...
19
votes
1answer
26k views

How to reduce number of sockets in TIME_WAIT?

Ubuntu Server 10.04.1 x86 I've got a machine with a FCGI HTTP service behind nginx, that serves a lot of small HTTP requests to a lot of different clients. (About 230 requests per second in the peak ...
18
votes
7answers
6k views

How to configure a shortcut for an SSH connection through a SSH tunnel

My company production servers (FOO, BAR...) are located behind two gateway servers (A, B). In order to connect to server FOO, I have to open a ssh connection with server A or B with my username ...
18
votes
3answers
33k views

Improving TCP performance over a gigabit network with lots of connections and high traffic of small packets

I’m trying to improve my TCP throughput over a “gigabit network with lots of connections and high traffic of small packets”. My server OS is Ubuntu 11.10 Server 64bit. There are about 50.000 (and ...
17
votes
20answers
2k views

Why does redhat seem to be so popular in the enterprise world?

Title says it all. For personal usage, I tend to prefer Debian/Ubuntu over Redhat. It's not necessarily that I dislike Redhat (or more specifically CentOS or Fedora) so much as it is that I like ...
17
votes
5answers
7k views

job scheduling using crontab, what will happen when computer is shutdown during that time?

I schedules some tasks using crontab. But, I am wondering what will happen if my computer is shutdown during the time or it was turned off before the time when it was schedule to do something ? Does ...
17
votes
9answers
6k views

Find last time update was performed with apt-get

I need to find the last time that the apt-get update command was run on my server. How can I determine this information?
17
votes
4answers
43k views

Why should I enable IO APIC in VirtualBox?

What are the advantages of checking the "Enable IO APIC" option in VirtualBox? While I can't find any information on advantages when I google it, two disadvantages are clear. First, it can break ...
17
votes
3answers
4k views

How do I reattach to Ubuntu Server's 'do-release-upgrade' process?

I accidentally pressed Ctrl+C during Ubuntu Server's do-release-upgrade process. I'd dropped to a shell to compare a .conf file in /etc/. When I pressed Ctrl-C, it asked whether I wanted to try to ...
17
votes
3answers
15k views

list all packages from a repository in ubuntu / debian

is there a command to see what packages are available from a certain ppa repository?
17
votes
3answers
8k views

On Ubuntu 10.04, should /etc/hostname contain the server's FQDN?

On Ubuntu 10.04, should /etc/hostname contain the server's fully-qualified domain name?