A family of Unix-like operating systems using the Linux kernel. If your question is about a certain distribution only, use a more specific tag.

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1441
votes
7answers
152k views

How do I make a machine “blank screen” for a period of time (as a penalty) if certain noise levels are reached?

My kids (4 and 5) yell a lot when playing games on the computer. I found an effective cure for this. When I hear loud noises, I ssh into the game computer and do: chvt 3; sleep 15; chvt 7 This ...
806
votes
8answers
575k views

How can I sort the output of 'ls' by last modified date?

How can I sort the output of ls by last modified date?
421
votes
9answers
41k views

Did I just get hacked?

I am developing a consumer product, and it is supposed to be connected to the Internet, so as expected, it is connected to the Internet so that I can properly develop it. I went away for an hour or ...
264
votes
5answers
615k views

How to find a directory on linux?

I have a VPS with Suse Linux 10.3. I've logged in via SSH/putty and am trying to find where my web files are located. Since I'm uploading via FTP in a directory called httpdocs, I assume that this ...
251
votes
4answers
62k views

How to turn off word-wrap in less

Short version: How can I make the less utility in Linux not wrap lines? Long version: Often I need to view huge CSV files using less with hundreds of columns. I frequently only care about the first ...
238
votes
27answers
136k views

How to execute a command whenever a file changes?

I want a quick and simple way to execute a command whenever a file changes. I want something very simple, something I will leave running on a terminal and close it whenever I'm finished working with ...
238
votes
8answers
250k views

What is the “You have new mail” message in Linux/UNIX?

Sometimes, when I log into a box and 'su' to root, I get a cute little message saying I have mail (thank GOD it's not AOL). Where is this mail? What does it contain? Who/What sent it? How important ...
214
votes
10answers
243k views

How to check which apache modules are enabled/installed?

Which is the most elegant way to check which apache modules are enabled?
197
votes
10answers
89k views

Get colors in less or more

When I read a file in Linux with the command less or more, how can I get the content in colors?
189
votes
18answers
24k views

What is the advantage of using 'tar' today?

I know that tar was made for tape archives back in the day, but today we have archive file formats that both aggregate files and perform compression within the same logical file format. Questions: ...
186
votes
5answers
200k views

How can I resume a stopped job in Linux?

How can I resume a stopped job in Linux? I was using emacs and accidentally hit ctrl-z which blasted me back to the console. I can see it when I type 'jobs' [*****]$ jobs [1]+ Stopped ...
185
votes
14answers
176k views

How do I detach a process from Terminal, entirely?

I use Tilda (drop-down terminal) on Ubuntu as my "command central" - pretty much the way others might use GNOME Do, Quicksilver or Launchy. However, I'm struggling with how to completely detach a ...
185
votes
8answers
13k views

What do the parentheses and number after a Unix command or C function mean?

I keep seeing parentheses and a number after a command in Unix or Linux or C function. For example: man(8), ftok(2), mount(8), etc. What do these mean? I see them in man too.
181
votes
3answers
189k views

Go back to previous directory in shell

Is there a way to go back to previous directory we were in using bash,tcsh without using pushd/popd ? I'd like to type something like "back" and got returned to the previous directory I was in. Edit: ...
180
votes
7answers
393k views

How to decompress a .bz2 file

I have a file as: filename.bz2 I need to decompress. I have tried the command: tar xvjf filename.tar.bz2, but it didn't work as the file is not a tar file. How do I decompress this file?
178
votes
8answers
297k views

How to get the summarized sizes of folders and their subfolders?

Let's say I want to get the size of each folder of a linux file system. When I use ls -la I don't really get the summarized size of the folders. If I use df I get the size of each mounted file system ...
176
votes
7answers
166k views

chown is not changing symbolic link

I'm trying to change the user/group of a symbolic link with the command: $ chown -h myuser:mygroup mysymbolic/ But it's not changing. I'm logged in as root. The current user/group is set to root:...
166
votes
11answers
242k views

How do I compare binary files in Linux?

I need to compare two binary files and get the output in the form <fileoffset-hex> <file1-byte-hex> <file2-byte-hex> for every different byte. So if file1.bin is 00 90 00 11 in binary ...
157
votes
8answers
147k views

View files in ZIP archive on Linux

How can I view the files in a ZIP archive without decompressing it?
154
votes
9answers
18k views

I accidentally typed password into bash command line

I accidentally typed my password into bash command line, mistaking the Last login: ... line for Wrong password (I was in a hurry). What do I do to cover my trace? What I did was editing .bash_history ...
153
votes
6answers
123k views

How do you gunzip a file and keep the .gz file?

The default behavior of gunzip is to delete the .gz file after it decompresses. How do I prevent it from deleting the file?? If this functionality is not included then is there an alternative ...
149
votes
3answers
63k views

What's the equivalent of Linux's updatedb command for the Mac?

If I want to use the locate command on a Linux machine, I usually run sudo updatedb first to update the database. I can run the locate command on OS X 10.5 but I can't find updatedb. What's the ...
148
votes
7answers
93k views

Automatically answer 'Yes' when using apt-get install

Is there a way to make apt-get install answer "yes" to the "Do you want to continue [y/N]?"?
140
votes
10answers
153k views

Is it possible to ping an address:port?

I am not into networking, and I have the following question related to the Linux ping command. Can I only ping an address? For example: miner@raspberrypi ~ $ ping onofri.org PING onofri.org (67.222....
140
votes
13answers
143k views

How to clear the contents of a file from the command line?

I have a log file that has a bunch of stuff in it that I don't need anymore. I want to clear the contents. I know how to print the contents to the screen: cat file.log I know how to edit the file, ...
139
votes
7answers
235k views

How do I find out what version of Linux I'm running?

Is there a way to determine what version (distribution & kernel version, I suppose) of Linux is running (from the command-line), that works on any Linux system?
133
votes
7answers
112k views

Why does Ctrl + V not paste in Bash (Linux shell)?

When I copy something to the clipboard and press Ctrl + V in Bash, nothing happens; However, right clicking and selecting Paste does the job. Why? Is there any reasonable issue (I'm sure there is) ...
131
votes
2answers
32k views

How to append to a file as sudo? [duplicate]

Possible Duplicate: sudo unable to write to /etc/profile I want to do: echo "something" >> /etc/config_file But, since only the root user has write permission to this file, I can't do ...
129
votes
13answers
84k views

How to reliably keep an SSH tunnel open?

I use an SSH tunnel from work to go around various idotic firewalls (it's ok with my boss :)). The problem is, after a while the ssh connection usually hangs, and the tunnel is broken. If I could at ...
128
votes
5answers
12k views

How does Linux know that the new password is similar to the previous one?

A few times I tried to change a user password on various Linux machines and when the new password was similar to the old one, the OS complained that they were too similar. I always wondered, how does ...
128
votes
3answers
189k views

ps aux output meaning

When typing ps aux, what does each column of the output mean? For example $ ps aux timothy 29217 0.0 0.0 11916 4560 pts/21 S+ 08:15 0:00 pine root 29505 0.0 0.0 38196 2728 ? ...
125
votes
3answers
53k views

Rename screen session

Is it possible to change the name of a GNU screen session? Say I called started it with "screen -S foo" and I want to rename it to bar.
124
votes
5answers
164k views

Permissions on private key in .ssh folder?

I changed my permissions in my .ssh folder and now when I use a piece of software that uses my private key, I have to type my password each time. What should my permissions be on my id_rsa file to ...
122
votes
9answers
9k views

What is the danger of inserting and browsing an untrusted USB drive?

Suppose someone wants me to copy some files to their USB stick. I'm running fully-patched Windows 7 x64 with AutoRun disabled (via Group Policy). I insert the USB drive, open it in Windows Explorer ...
122
votes
5answers
273k views

How can I list all IPs in the connected network, through Terminal preferably?

Using Ubuntu 10.10, I was wondering if there was a command line command that can list all the IPs of devices connected to the network? I would use this for example, to list all the computers ...
122
votes
5answers
12k views

How to identify whether my Linux computer was hacked?

My home PC is usually on, but the monitor is off. This evening I came home from work and found what looks like a hack attempt: in my browser, my Gmail was open (that was me), but it was in compose ...
116
votes
5answers
109k views

Recursively count all the files in a directory [duplicate]

Possible Duplicate: How can I count the number of folders in a drive using Linux? I have a really deep directory tree on my Linux box. I would like to count all of the files in that path, ...
116
votes
9answers
12k views

Why is Zip able to compress single file smaller than multiple files with the same content?

Suppose that I have 10,000 XML files. Now suppose that I want to send them to a friend. Before sending them, I would like to compress them. Method 1: Don't compress them Results: Resulting Size: ...
114
votes
7answers
193k views

If I know the PID number of a process, how can I get its name?

If I have the PID number for a process (on a UNIX machine), how can I find out the name of its associated process? What do I have to do?
113
votes
8answers
69k views

Reload a Linux user's group assignments without logging out

When assigning a user's secondary group list using: # usermod -G <grouplist> <user> is it possible to force this group assignment to take effect without logging out all running sessions?...
113
votes
3answers
146k views

How to convert .ppk key to OpenSSH key under Linux?

I know that is possible to convert .ppk under puttygen in Windows, but how to do that on Linux? Is this possible ?
112
votes
9answers
294k views

How do I get an entire directory in sftp?

I'm just learning to use sftp, and I want to copy a directory from the remote computer to my local computer. If I try get [directory] it gives me this error: Cannot download non-regular file: /...
112
votes
14answers
290k views

How do I figure out which /dev is a USB flash drive?

I want to mount a USB drive, two of them and I need two different mount points. Unfortunately, the Linux kernel underwent a name change and I can't figure out which /dev location is the right one. Is ...
112
votes
9answers
430k views

How to install the real Firefox on Debian?

Debian 6 ("Squeeze") uses a rebranded version of Firefox called Iceweasel. It, however, lacks plugin support, and most of my favorites don't work. So what is best way to install the "real" Firefox on ...
111
votes
6answers
312k views

How can I give write-access of a folder to all users in linux?

I installed apache2 on Ubuntu just now, and noticed that the /var/www folder is protected. I can just sudo everything but I would rather just give it write access. How can I do this? I tried sudo ...
106
votes
16answers
89k views

How to delete all files in a directory except some?

I need to delete all files in a directory, but exclude some of them. For example, in a directory with the files a b c ... z, I need to delete all except for u and p. Is there an easy way to do this?
106
votes
16answers
172k views

How to wipe free disk space in Linux?

When a file is deleted, its contents may still be left in the filesystem, unless explicitly overwritten with something else. The wipe command can securely erase files, but does not seem to allow ...
104
votes
7answers
48k views

What is the difference between executing a bash script and sourcing a bash script?

What is the difference between executing a bash script like A and sourcing a bash script like B? A >./myscript B >source myscript
102
votes
7answers
32k views

How can I create a file with a specific size from a command line?

How can I create a file (e.g. using the touch command or another similar way), but with a specific size (e.g. 14 MB)? The use case is to test FTP with various file sizes. If we can create a file with ...
101
votes
8answers
118k views

Batch converting PNG to JPG in linux

Does anyone know a good way to batch-convert a bunch of PNGs into JPGs in linux? (I'm using Ubuntu). A png2jpg binary that I could just drop into a shell script would be ideal.