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Questions tagged [linux]

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.

1537
votes
6answers
157k 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 ...
1302
votes
9answers
1.0m 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?
486
votes
9answers
51k 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 ...
421
votes
5answers
991k 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 ...
400
votes
4answers
118k 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 ...
387
votes
33answers
279k 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 ...
384
votes
7answers
468k 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 ...
369
votes
14answers
180k 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?
355
votes
11answers
444k views

How to check which apache modules are enabled/installed?

Which is the most elegant way to check which apache modules are enabled?
337
votes
10answers
349k views

View list of files in ZIP archive on Linux

How can I view the list of files in a ZIP archive without decompressing it?
329
votes
6answers
777k 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?
314
votes
10answers
245k 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]?"?
312
votes
5answers
379k 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 ...
307
votes
5answers
336k 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 ...
288
votes
9answers
287k 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:...
286
votes
12answers
184k 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? ...
285
votes
18answers
304k 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 ...
282
votes
11answers
695k views

Test if a port on a remote system is reachable (without telnet)

In the old days, we used telnet to see if a port on a remote host was open: telnet hostname port would attempt to connect to any port on any host and give you access to the raw TCP stream. These days,...
281
votes
6answers
397k 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: ...
271
votes
14answers
423k 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 ...
269
votes
9answers
514k views

How to get the summarized sizes of directories and their subdirectories?

Let's say I want to get the size of each directory 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 ...
249
votes
14answers
310k 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, ...
238
votes
8answers
73k views

How to append to a file as sudo?

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 that. But the following also doesn't work. sudo echo "something" ...
236
votes
7answers
108k views

What is the difference between executing a Bash script vs sourcing it?

What is the difference between executing a Bash script like A and sourcing a Bash script like B? A > ./myscript B > source myscript
221
votes
4answers
99k 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 ...
221
votes
10answers
456k 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?
209
votes
15answers
157k 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 ...
209
votes
7answers
193k 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 ...
208
votes
8answers
17k 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.
206
votes
18answers
34k 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: ...
203
votes
8answers
527k 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 ...
202
votes
7answers
534k views

How do I exit a SSH connection?

I’m connecting to a server via SSH to send a message to a socket server using a command like: ssh 181.169.1.2 -p 5566 After the connection is established and I write the message and send it I can’...
202
votes
3answers
313k 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 ? ...
201
votes
11answers
368k 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....
199
votes
9answers
395k 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?
185
votes
11answers
26k 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 ...
181
votes
3answers
90k 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.
178
votes
7answers
212k 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) ...
174
votes
5answers
204k 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, ...
174
votes
8answers
544k 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 ...
171
votes
9answers
440k 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: /home/...
166
votes
4answers
239k 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 ?
165
votes
5answers
483k views

Get a list of Open Ports in Linux

I need a Linux command to list all free open ports for use in an application lsof -i TCP| fgrep LISTEN Does not seen to be helping as the Ports it lists are not necessarily free for use. How do I ...
164
votes
10answers
294k views

How to copy symbolic links?

I have directory that contains some symbolic links: user@host:include$ find .. -type l -ls 4737414 0 lrwxrwxrwx 1 user group 13 Dec 9 13:47 ../k0607-lsi6/camac -> ../../include 4737415 ...
157
votes
6answers
142k views

How to have Linux ls command show second in time stamp

Something annoying about ls -l command is it shows only hour and minute for a file(like 08:30). How can I see the second portion(like 08:30:44)? man 1 ls and search for 'second' does not give any ...
156
votes
13answers
429k 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 ...
151
votes
9answers
191k views

What to do when Ctrl + C can't kill a process?

Ctrl + C doesn't always work to kill the current process (for instance, if that process is busy in certain network operations). In that case, you just see "^C" by your cursor and can't do much else. ...
150
votes
2answers
194k views

Linux unzip command: Option to force overwrite?

I am writing a shell script that unzips a ZIP file into an existing hierarchy of files, potentially overwriting some of the files. The problem is that the unzip command asks for confirmation: replace ...
145
votes
10answers
189k 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.
142
votes
7answers
143k views

How can I avoid SSH's host verification for known hosts?

I get the following prompt everytime I try to connect a server using SSH. I type "yes", but is there a way to aovid this? The authenticity of host '111.222.333.444 (111.222.333.444)' can't be ...