Ubuntu is a Linux distribution with an emphasis on ease of use and installation. Note that http://askubuntu.com is specifically dedicated to Ubuntu questions.

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65
votes
11answers
191k views

How do I set my DNS on Ubuntu 14.04?

Most of the info I see online says to edit /etc/resolv.conf, but any changes I make there just get overridden. $ cat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by ...
62
votes
20answers
10k views

Root access that can't change root password?

We are having a little problem on a server. We want that some users should be able to do e.g. sudo and become root, but with the restriction that the user can't change root password. That is, a ...
59
votes
7answers
21k views

What is the Linux equivalent to C:\Program Files?

I understand that in Windows as well as Linux and Unix, a program|application|software can be installed in any directory. Also if packages are installed using the distribution's packaging system, ...
38
votes
1answer
10k views

What is $debian_chroot in .bashrc?

What is the debian_chroot variable in my bashrc file? and what is it doing here? PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
37
votes
2answers
36k views

How do I run 32-bit programs on a 64-bit Debian/Ubuntu?

I have a 64-bit (amd64 a.k.a. x86_64) Debian or Ubuntu installation. I need to run 32-bit (i386/i686) programs occasionally, or to compile programs for a 32-bit system. How can I do this with a ...
33
votes
8answers
13k views

List explicitly installed packages

In Gentoo there is the file /var/lib/portage/world that contains packages that I explicitly installed. By explicit I mean, packages that I choose, not including anything installed by default, or ...
31
votes
8answers
25k views

Differences between Debian and Ubuntu

I'm getting sick of Ubuntu's seemingly random changes. I'm thinking of switching to Debian permanently. Does anyone know if there's a list of changes between the two distros somewhere? I want to know ...
29
votes
4answers
34k views

How can I update to a newer version of Git using apt-get?

I've just set up a new machine with Ubuntu Oneiric 11.10 and then run apt-get update apt-get upgrade apt-get install git Now if I run git --version it tells me I have git version 1.7.5.4 but on my ...
29
votes
2answers
70k views

How can I restart the SSH daemon on Ubuntu?

When I type in service sshd restart I get a sshd: unrecognized service error. I do have, in /etc/ssh/ a file sshd_config that I use to set config. I can also putty into the Ubuntu box (it is remote). ...
29
votes
1answer
17k views

What does adduser do that useradd doesn't?

In addition to the more widespread useradd, Debian based systems also contain an additional adduser command which provides a higher level interface for adding users and some related tasks. There are ...
27
votes
9answers
2k views

Uninstalling programs on Linux

I've been using Windows and Mac OS for the past 5 years and now I'm considering to use Linux on a daily basis. I've installed Ubuntu on a virtual machine and trying to understand how I can use Linux ...
27
votes
5answers
21k views

How can I play a sound when script execution is ready?

I am executing every now and then some python scripts which take quite long to execute. I execute them like this: $ time python MyScript.py How can I play a sound as soon as the execution of the ...
27
votes
7answers
7k views

Force directory to always be in cache

I've been testing out different methods to improve the time it takes to compile my entire c++ project. Currently it takes ~5 minutes. I experimented with distcc, ccache, and others. Recently, I ...
26
votes
6answers
57k views

File permission issues with shared folders under Virtual Box (Ubuntu Guest, Windows Host)

I am using Ubuntu on Virtual Box and I have a folder which is shared between the host (Windows) and the VM (Ubuntu). When I open any file in the share folder in Ubuntu, I can not change it as its ...
25
votes
3answers
98k views

“Input/output error” when accessing a directory

I want to list and remove the content of a directory on a removable hard drive. But I have experienced "Input/output error": $ rm pic -R rm: cannot remove `pic/60.jpg': Input/output error rm: cannot ...
24
votes
6answers
3k views

Why is it risky to give sudo vim access to ordinary users?

I'd like to create a new user and give him sudo access. To be specific, I want him to use sudo vim and edit httpd.conf. I wrote this in sudoers: user ALL=(ALL) /usr/bin/vim ...
23
votes
5answers
10k views

What is the difference between ls and l?

I accidentally typed l instead of ls today and found that the command still printed a list of the files in my current directory. Trying l --help brings up the help file for ls suggesting that l is ...
23
votes
5answers
24k views

rsync all files of remote machine over SSH without root user?

I have this command to backup a remote machine. The problem is that I need root rights to read and copy all files. I have no root user enabled for security reasons and use sudo the Ubuntu way. Would I ...
23
votes
4answers
69k views

SSH login with clear text password as a parameter?

I need to login to a user that I've created on a remote host running Ubuntu. I can't use an ssh key because the ssh login will happen from a bash script ran within a server that I won't have access to ...
23
votes
2answers
53k views

Sorting down processes by memory usage

I am able to see the list of all the processes and the memory via ps aux and going through the VSZ and RSS Is there a way to sort down the output of this command by the descending order on RSS ...
23
votes
4answers
53k views

Shell script fails: Syntax error: “(” unexpected

I've been working on a script that automates setting up a development environment for Raspberry Pi development (step by step details that work are here). The script is linked in that article but ...
22
votes
4answers
10k views

What doesn't need defragmentation? Linux or the ext2 ext3 FS?

Why don't you have to defrag a Linux system? Because it's using the ext2/ext3 file system or because it's Linux? That's relevant, because a have a double boot system (W7 / Ubuntu) and a common ...
22
votes
2answers
9k views

Run script on screen lock/unlock

I'd like to run a screen if the Gnome session is locked and unlocked. Is there a way that I can intercept this and perform certain actions when the desktop is locked or unlocked?
20
votes
1answer
4k views

Meaning of colours in htop

Given the option: [ ] Detailed CPU time (System/IO-Wait/Hard-IRQ/Soft-IRQ/Steal/Guest) In htop (Version 1.0.1) what are the meanings of the colours? In the following image, I'm seeing rather a lot ...
20
votes
4answers
23k views

How to record Skype video calls on Linux?

I'd like to conduct recorded video interviews with Skype and am looking for a reliable tool to accomplish that. Is there anything out there that's not slow or buggy? I'm running (K)Ubuntu.
19
votes
6answers
43k views

Ubuntu12.04: How to disable a daemon process at startup

I normally use service start/stop or initctl start/stop to start or stop a daemon process but now what I am looking for is to disable a daemon process from starting at startup example mysqld. ...
19
votes
4answers
3k 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 ...
18
votes
2answers
2k views

Is there an online/web interface to search and list apt-get packages and see summaries and recommendations?

I'm looking for sort of an 'app-store' or Google Play store type functionality for apt-get packages. What I'd really like to do is select a category, like 'Music' or 'Internet' and see the list of ...
18
votes
3answers
2k views

How to prevent shutdown when an SSH user is logged in?

I'm administrating a networked environment and I had an interesting situation arise yesterday. When a host is required to shutdown by a regular user, it refuses to do so if other users are logged in ...
17
votes
3answers
8k views

bulk rename (or correctly display) files with special characters

I have a bunch of directories and subdirectories that contain files with special characters, like this file: robbie@phil:~$ ls test�sktest.txt test?sktest.txt Find reveals an escape sequence: ...
16
votes
5answers
4k views

Advantages of Debian over Ubuntu

What are the main advantages of using Debian instead of Ubuntu?
16
votes
2answers
17k views

Zip everything in current directory

I'd like to compress and package everything, including files and folders in current directory, into a single ZIP file on Ubuntu. What would be the most convenient command for this (and name of the ...
15
votes
5answers
29k views

delete line in vi

How can I delete a line in VI? Here what I am doing right now: Open up the terminal alt + ctrl + t vi a.txt I move my cursor to the line which I wan to delete, then what key-combination is should ...
15
votes
3answers
11k views

LXC: How do I mount a folder from the host to the container?

I'm trying to mount a folder on the host to an LXC container. The host has a folder /mnt/ssd/solr_data created (this is currently on the root filesystem, but later I'll mount an SSD drive there, so ...
15
votes
2answers
11k views

What is the “/usr/local/src” folder meant for?

I wanted to put my work files (code) in /usr/local/src, but I think it's already a folder that has some other semantic meaning. What is that? Should I put source code there, or is there a better ...
15
votes
5answers
15k views

Why doesn't docker container start at boot w/ upstart script on Ubuntu 12.04?

Using instructions for Docker auto-start on Linode VPS running Ubuntu 12.04 and Docker 0.8.1, the specified container does not start on reboot. Once booted, I am able to ~$ sudo start [service-name] ...
14
votes
4answers
483 views

What specific vulnerabilities am I creating by disabling the sudo password?

Here are some instructions on how to disable your sudo password. These carry the following warning If you disable the sudo password for your account, you will seriously compromise the security of ...
14
votes
2answers
6k views

(SSH) Is it dangerous to close terminal without “exit”?

This happened many times. While the SSH active, I'm so tired and just close the terminal without exit Is it dangerous to doing like that?
14
votes
3answers
30k views

VirtualBox: two network interfaces (NAT and host-only ones) in a Debian guest on Ubuntu

I created a Debian VM on VirtualBox with two interfaces: a NAT one (for accessing internet) and a host-only one. However, I do not know how to make both interfaces work at the same time. If I the ...
14
votes
1answer
4k views

What happens in each step of the Linux kernel-building process?

I've read many tutorials about how to build custom kernels and boot Ubuntu using those kernels, and successfully followed the guides and booted custom kernels, but I have no understanding about what ...
14
votes
3answers
11k views

What is the proper way to manage multiple python versions?

I have a machine with Python 2.6 installed as the default Python. Then, I installed Python 2.7, and manually created /usr/bin/python as a symlink to the new installation. Then, I was running into ...
14
votes
1answer
732 views

How do command-line tools have their own autocomplete list?

How does Bash in Ubuntu know a tool's specific list of actions? For example if I type apt-get and tab twice I only see remove, update, upgrade ...etc, but not the actions for another command or the ...
14
votes
1answer
6k views

What does a kernel source tree contain? Is this related to Linux kernel headers?

In books, I typically read references to the Linux Source Tree at /usr/src/linux with the usual set of subdirectories (arch, block, crypto, ...). I was expecting this tree to contain the binary files ...
14
votes
3answers
5k views

Are multiple @daily crontab entries processed in order, serially?

I want two jobs to run sometime every day, serially, in exactly the order I specify. Will this crontab reliably do what I want? @daily job1 @daily job2 I'm assuming they run one after the other, ...
13
votes
4answers
2k views

Is there a way to auto turn-on Ubuntu?

Like a command line or a small piece of software I know that there are many ways to auto-shutdown, but I'm concerned about auto-turn-on.
13
votes
6answers
2k views

Is there a root password on OS X and Ubuntu?

When you setup a new Ubuntu or OS X installation a user is generally created for you. On OS X it is whatever username you pick. On Ubuntu (the server version) usually the ubuntu user is created. The ...
13
votes
3answers
2k views

How can I de-fragment a drive using Ubuntu?

Is it necessary to defrag drives in Ubuntu? If so, how do I do it and how often should it be done?
13
votes
4answers
46k views

How can I look up a username by id in linux?

The command id can be used to look up a user's uid, for example: $ id -u ubuntu 1000 Is there a command to lookup up a username from a uid? I realize this can be done by looking at the /etc/passwd ...
13
votes
4answers
26k views

What program do I use to check mail?

I'm receiving "You have mail" messages and according to How to remove “You have mail” welcome message I should read my mail with mail. However I cannot find the command in my system (Ubuntu 10.04 ...
13
votes
5answers
20k views

keyserver timed out when trying to add a GPG public key

I am trying to add a public key for installing a program with CPG. But i am pretty new to this but every command i found gave me the same error: gpg --keyserver keyserver.ubuntu.com --recv-keys ...