1.&lt;kbd&gt;Control&lt;/kbd&gt;+&lt;kbd&gt;a&lt;/kbd&gt;, then &lt;kbd&gt;Escape&lt;/kbd&gt;. &lt;br&gt;2. after that, you should be able to move your cursor around using the arrow keys:&lt;br&gt;&lt;kbd&gt;&amp;uarr;&lt;/kbd&gt;, &lt;kbd&gt;&amp;darr;&lt;/kbd&gt;, &lt;kbd&gt;PgUp&lt;/kbd&gt;, &lt;kbd&gt;PgDn&lt;/kbd&gt; and sometimes works mouse wheel
&lt;br&gt;
3. return control: &lt;kbd&gt;q&lt;/kbd&gt; or &lt;kbd&gt;Esc&lt;/kbd&gt;

Press &lt;kbd&gt;Ctrl&lt;/kbd&gt;-&lt;kbd&gt;a&lt;/kbd&gt; then &lt;kbd&gt;[&lt;/kbd&gt; will enter the copy mode, and you can scroll up and down like _vim_ editor.
Leave the copy mode by pressing &lt;kbd&gt;Escape&lt;/kbd&gt;.

&lt;kbd&gt;Ctrl&lt;/kbd&gt;-&lt;kbd&gt;a&lt;/kbd&gt; (default prefix) + &lt;kbd&gt;[&lt;/kbd&gt;: Enter copy mode.

&lt;kbd&gt;Esc&lt;/kbd&gt;: Quit copy mode.

Within copy mode:

&lt;kbd&gt;Ctrl&lt;/kbd&gt;-&lt;kbd&gt;u&lt;/kbd&gt;, &lt;kbd&gt;Ctrl&lt;/kbd&gt;-&lt;kbd&gt;d&lt;/kbd&gt;: Page up/down by certain amount of lines while preserving cursor position (default by half of the screen)

&lt;kbd&gt;Ctrl&lt;/kbd&gt;-&lt;kbd&gt;b&lt;/kbd&gt;, &lt;kbd&gt;Ctrl&lt;/kbd&gt;-&lt;kbd&gt;f&lt;/kbd&gt;: Page up/down by a full screen

Use &lt;kbd&gt;CTRL&lt;/kbd&gt; + &lt;kbd&gt;A&lt;/kbd&gt;, then &lt;kbd&gt;Escape&lt;/kbd&gt; to enter in &quot;_Copy mode_&quot;. After that, you should be able to move your cursor around using the arrow keys. To exit, press &lt;kbd&gt;Escape&lt;/kbd&gt; again.

Another way is to do the following to use *Mouse Scrollwheel*:

    echo &#39;termcapinfo xterm* ti@:te@&#39; &gt;&gt; ~/.screenrc

Scrolling works in screen with &#39;terminator&#39; in ubuntu.

    sudo apt-get install terminator

I&#39;ve been reading `passport.js` info and samples for two days, but I&#39;m not sure after that I did all the process of authenticating. 

How do I know if I&#39;m logged in, for example, I&#39;ll have a navigation bar with a login or logout button, is there some variable like code below?

    if (login)
       &lt;button&gt;logout&lt;/button&gt;
    else 
       &lt;button&gt;login&lt;/button&gt;

How to know if user is logged in with passport.js?

In Unix shell, I have a env file (*env file defines the parameters required for running the user script like log file name and path, redirect outputs and errors to log file, database connection details, etc*) which redirects all the outputs (*echo messages*) and errors to the log file from the executed script using the following code:

    exec 1&gt;&gt;${LOG_FILE}
    exec 2&gt;&gt;${LOG_FILE}

 
The env file is executed at the beginning of each script. Due to the above code in env file all the console outputs that might be user outputs or errors are directly output to the log file which is what I actually needed.

But there are some selective user outputs which I want to be displayed in both the console and the log file. But because of the above code I am not able to do so.

I know that if I remove the above code I can get the desired result for this case, but I will have to manually write all other outputs to the log file which is not an easy task.

Is there a way to get the output in both the console and the log file without removing the above codes?


 

Writing outputs to log file and console

I just installed `screen` and like the idea to divide linux terminal into multiple pieces. But I can&#39;t figure out one thing: How to scroll up and down, when I&#39;m in `screen`. When I&#39;m using regular linux terminal I can achieve this with &lt;kbd&gt;Shift&lt;/kbd&gt; + &lt;kbd&gt;Pg Up&lt;/kbd&gt; or &lt;kbd&gt;Shift&lt;/kbd&gt; + &lt;kbd&gt;Pg Dn&lt;/kbd&gt;`. but unfortunatelly it doesn&#39;t work in divided terminal.

That&#39;s what I mean when saying `screen` and divided terminal:
![enter image description here][1]


And that&#39;s a regular termina (just in case):
![enter image description here][2]


  [1]: http://i.stack.imgur.com/0N9vH.png
  [2]: http://i.stack.imgur.com/586le.png

How to scroll up and down in sliced &quot;screen&quot; terminal

I just installed <code>screen</code> and like the idea to divide linux terminal into multiple pieces. But I can't figure out one thing: How to scroll up and down, when I'm in <code>screen</code>. When I'm using regular linux terminal I can achieve this with <kbd>Shift</kbd> + <kbd>Pg Up</kbd> or <kbd>Shift</kbd> + <kbd>Pg Dn</kbd>`. but unfortunatelly it doesn't work in divided terminal.
That's what I mean when saying <code>screen</code> and divided terminal:
<img src="http://i.stack.imgur.com/0N9vH.png" alt="enter image description here">
And that's a regular termina (just in case):
<img src="http://i.stack.imgur.com/586le.png" alt="enter image description here">

In my `.bashrc` I define a function which I can use on the command line later:

    function mycommand() {
        ssh user@123.456.789.0 cd testdir;./test.sh &quot;$1&quot;
    }


When using this command, just the `cd` command is executed on the remote host; the `test.sh` command is executed on the local host. This is because the semicolon separates two different commands: the `ssh` command and the `test.sh` command. 

I tried defining the function as follows (note the single quotes):

    function mycommand() {
        ssh user@123.456.789.0 &#39;cd testdir;./test.sh &quot;$1&quot;&#39;
    }

I tried to keep the `cd` command and the `test.sh` command together, but the argument `$1` is not resolved, independent of what I give to the function. It is always tried to execute a command

    ./test.sh $1

on the remote host. 

How do I properly define `mycommand`, so the script `test.sh` is executed on the remote host after changing into the directory `testdir`, with the ability to pass on the argument given to `mycommand` to `test.sh`?

How to execute a remote command over ssh with arguments?

This may sound silly, but I have a file/ script that need to run and in order to do it I must change it to become executable. I would want to use either `chmod a+x` or `chmod 755`. But is there a difference between using `chmod a+x` and `chmod 755`?


Difference between using &quot;chmod a+x&quot; and &quot;chmod 755&quot;

I&#39;m currently using tmux with xterm-256color $TERM variable. When in bash under tmux, pressing home/end would insert tilde characters (~). Outside of tmux the home/end keys work fine. 

Using cat and tput, I could see that there was a mismatch between the generated and expected sequences:

    $ cat -v # pressing home, then end
    ^[[1~^[[4~
    $ tput khome | cat -v; echo
    ^[OH
    $ tput kend | cat -v; echo
    ^[OF

To fix this, I decided to add the following to my .bashrc:

    if [[ -n &quot;$TMUX&quot; ]]; then
        bind &#39;&quot;\e[1~&quot;:&quot;\eOH&quot;&#39;
        bind &#39;&quot;\e[4~&quot;:&quot;\eOF&quot;&#39;
    fi

That fixed the problem for bash, however in other readline programs, such as within a REPL such as ipython, it still inserts a tilde for home/end. 

Why exactly is this a problem in the first place? Why is the generated sequence different when I&#39;m inside tmux vs outside it? How can fix this so that it&#39;s not an issue in any programs?

Home/End keys do not work in tmux

I have a simple BASH command that looks like

    for i in `seq 2`; do echo $i; done; &gt; out.dat

When this runs the output of `seq 2` is output to the terminal and nothing is output to the data file (out.dat)

I am expecting standard out to be redirected to out.dat like it does simply running the command `seq 2 &gt; out.dat`



Redirecting output of bash for loop

I&#39;m trying to find a line in a file and replace the next line with a specific value. I tried sed, but it seems to not like the \n. How else can this be done?

The file looks like this:

    &lt;key&gt;ConnectionString&lt;/key&gt;
    &lt;string&gt;anything_could_be_here&lt;/string&gt;

And I&#39;d like to change it to this

    &lt;key&gt;ConnectionString&lt;/key&gt;
    &lt;string&gt;changed_value&lt;/string&gt;

Here&#39;s what I tried:

    sed -i &#39;&#39; &quot;s/&lt;key&gt;ConnectionString&lt;\/key&gt;\n&lt;string&gt;&lt;\/string&gt;/&lt;key&gt;ConnectionString&lt;\/key&gt;\n&lt;string&gt;replaced_text&lt;\/string&gt;/g&quot; /path/to/file

find matching text and replace next line

When I restart the nginx service on a command line on an Ubuntu server, the service crashes when a nginx configuration file has errors. On a multi-site server this puts down all the sites, even the ones without configuration errors.

To prevent this, I run the nginx configuration test first:

    nginx -t

After the test ran successful, I could restart the service:

    /etc/init.d/nginx restart

**Or** only reload the nignx site configs without a restart:

    nginx -s reload

Is there a way to combine those two commands where the restart command is conditional to the configuration test&#39;s result?

I couldn&#39;t find this online and [the official documentation][1] on this is rather basic. I don&#39;t know my way around Linux that well, so I don&#39;t know if what I&#39;m looking for is right in front of me or not possible at all.

I&#39;m using nginx v1.1.19.

  [1]: http://wiki.nginx.org/CommandLine



How do I restart nginx only after the configuration test was successful on Ubuntu?

I am getting the &quot;No space left on device&quot; error for pretty much anything i try to do. Even using tab to autocomplete a command!

but when i do df -h i get:

    ubuntu@ip-10-0-2-108:~$ df -h
    Filesystem      Size  Used Avail Use% Mounted on
    /dev/xvda1       99G  6.5G   88G   7% /
    udev            3.7G  8.0K  3.7G   1% /dev
    tmpfs           1.5G  184K  1.5G   1% /run
    none            5.0M     0  5.0M   0% /run/lock
    none            3.7G     0  3.7G   0% /run/shm
    none            100M     0  100M   0% /run/user
    /dev/xvdb       414G  199M  393G   1% /mnt
    overflow        1.0M  1.0M     0 100% /tmp

which to me looks like there is tons of space. df -i also looks similar:

    ubuntu@ip-10-0-2-108:~$ df -i
    Filesystem       Inodes IUsed    IFree IUse% Mounted on
    /dev/xvda1      6553600 94227  6459373    2% /
    udev             951353   393   950960    1% /dev
    tmpfs            953649   274   953375    1% /run
    none             953649     3   953646    1% /run/lock
    none             953649     1   953648    1% /run/shm
    none             953649     1   953648    1% /run/user
    /dev/xvdb      27525120    11 27525109    1% /mnt
    overflow         953649    12   953637    1% /tmp

I am on an Amazon EC2 ubuntu 12.04 instance.

Here are some examples of the error popping up:

    ubuntu@ip-10-0-2-108:~$ sudo crontab -e
    /tmp/crontab.RvYjrR/crontab: No space left on device

    ubuntu@ip-10-0-2-108:~$ ls /va (hit tab for autocomplete)
    
    -bash: cannot create temp file for here-document: No space left on device
    -bash: cannot create temp file for here-document: No space left on device

however the server seems to be running and everything seems to be working.
what on earth is going on??




ubuntu &quot;No space left on device&quot; but there is tons of space

I am trying to use 

    sudo npm install
to install all my dependencies for an application written in nodejs. My OS is Ubuntu 13.04

However, I keep getting this warning:

    The authenticity of host &#39;github.com (192.30.252.131)&#39; can&#39;t be established.
    RSA key fingerprint is 16:27:ac:a5:76:28:1d:52:13:1a:21:2d:bz:1d:66:a8.
    Are you sure you want to continue connecting (yes/no)?

Has anyone encountered this warning before? Is it possible to authenticate and store the fingerprint locally? So I won&#39;t need to authenticate again when I enter sudo npm install another time. 

Right now, I am unable to enter anything, not even &quot;yes&quot;. My terminal just gets stuck, i have to press &lt;kbd&gt;Ctrl&lt;/kbd&gt;+&lt;kbd&gt;C&lt;/kbd&gt; to terminate.


The authenticity of host &#39;github.com (192.30.252.128)&#39; can&#39;t be established

I am new to system administration. After installing nginx [via puppet][1] on Ubuntu I get the following output:

    [alert] could not open error log file: open() &quot;/var/log/nginx/error.log&quot; failed (13: Permission denied)
    
    [warn] 1898#0: the &quot;user&quot; directive makes sense only if the master process runs with super-user privileges, ignored in /etc/nginx/nginx.conf:1
    
    [emerg] 1898#0: open() &quot;/var/log/nginx/access.log&quot; failed (13: Permission denied)

How do I get rid of all of these messages?

I don&#39;t want to use command line directly (chown / chmod) and repeat it every time I create a new server. Therefore, I am thinking of what has to be added to the puppet manifest.

What is the best sysadmin practice in this case: to change owner / permissions for /var/log/nginx or to store logs in different location? If chown / chmod is the way to go, which specific permissions would ensure the highest level of security?

I tried this, but it didn&#39;t help:

      file { &#39;/var/log/nginx&#39;:
        ensure  =&gt; directory,
        mode    =&gt; &#39;0755&#39;,
        owner   =&gt; &#39;www-data&#39;,
        group   =&gt; &#39;www-data&#39;,
        recurse =&gt; true
      }

Edited:

    vagrant@precise64:~$ ps aux | grep [n]ginx
    root      1001  0.0  0.1  62908  1388 ?        Ss   08:47   0:00 nginx: master process /usr/sbin/nginx
    www-data  1002  0.0  0.1  63260  1696 ?        S    08:47   0:00 nginx: worker process
    www-data  1003  0.0  0.1  63260  1696 ?        S    08:47   0:00 nginx: worker process
    www-data  1004  0.0  0.1  63260  1696 ?        S    08:47   0:00 nginx: worker process
    www-data  1005  0.0  0.1  63260  1696 ?        S    08:47   0:00 nginx: worker process

  [1]: https://github.com/kasperisager/puppet-nginx


Nginx: Permission denied for nginx on Ubuntu

I am using Ubuntu 12.04 and Postgress 9.2.

I need to create this user with this password e.g.

    postgres://admin:test101@127.0.0.1:5432

How to do that from the command line?  I need to automate with a bash script.  I have a fresh install.

How to create a user for Postgres from the command line for bash automation

I&#39;m trying to find UNIX or bash command to run a command after connecting to an ssh server.  For example:

    ssh name@ip &quot;tmux list-sessions&quot;

The above code works, it lists the sessions, but it then immediately disconnects.  Putting it in the sshrc on the server side works, but I need to be able to type it in client side.  I want to be able to run a command, it logs in, opens up the window, then runs the command I&#39;ve set. Ive tried 

    [command] | ssh name@ip

    ssh name@ip [command]

    ssh name@ip &quot;[command]&quot;

    ssh -t name@ip [command]

Run ssh and immediately execute command

I&#39;m debugging a shell script and trying to find out the task performed by the following command:

    sed -i &#39;1,+999d&#39; /home/org_user/data.txt

I need to change this command as its failing with the following error:

    illegal option sed -i

But before changing, I need to understand the BAU functioning.

Appreciate any inputs in this regard.

What does sed -i option do?

In my bash script I do:

    mkdir product;

When I run the script more than once I get:

    mkdir: product: File exists

In the console.

So I am looking to only run mkdir if the dir doesn&#39;t exist.  Is this possible?

Only mkdir if it does not exist

What is the difference between assigning to a variable like `var=foo` and using let like `let var=foo`? Or cases like `var=${var}bar` and `let var+=bar`? What are the advantages and disadvantages of each approach?

Bash: let statement vs assignment

As I write my bash scripts for my OS X that do general things, I am wondering where is a good place to keep them. Is there a directory I can put them all in where they will be picked up automatically?  Or should I create my own directory and then reference this directory from .profile or something?


Where do you keep your own scripts on OSX?

How would I change all files to 644 and all folders to 755 using `chmod` from the `linux` command prompt? (Terminal)



Change all files and folders permissions of a directory to 644/755

I have no real idea what I&#39;m doing here so please bear that in mind if you can help me!

I am trying to connect to my virtual server through a proxy but I can&#39;t connect, it just hangs. I&#39;m assuming this is because it&#39;s not getting through our proxy.

I have tried exactly the same thing at home and it works perfectly. I&#39;m on OSX using Terminal to connect.

Can anyone advise me how I can get through the proxy with SSH?

Connect with SSH through a proxy

I want to disable beep sound in terminal. Im not able to find an option to disable the beep sound in preferences. Could you please help me out?

-cherryhitech

I want to disable beep sound in Terminal - Mac OSX

I&#39;m trying to set-up Sublime Text 3 on OS X Mavericks and getting levels of frustration. 

I&#39;ve followed all of the usual suspects in regards to installation and setup, i.e. Googling the Sublime Text website, and Stack Overflow. Inevitably it&#39;s something minor I&#39;m missing, but it&#39;s causing me major heartburn.

What I&#39;ve done so far:

 1. Downloaded Sublime Text 3, sitting in my /Applications directory
 2. Followed the guide [Launch Sublime Text 2 from Mac Terminal][1] 
      
The problems starts here. I know that the symlink presented in this link is using ST2, but I want to use &quot;`sublime`&quot; instead of the &quot;`subl`&quot;(personal preference). I searched around and found what I need to paste into Terminal for ST3:
    
    ln -s &quot;/Applications/Sublime Text.app/Contents/SharedSupport/bin/subl&quot; ~/usr/local/bin/sublime
 
 3. Already had a ~/.bash_profile: `export PATH=/usr/local/bin:$PATH`. However, when I `echo $PATH` I get:

        /usr/local/bin:/usr/local/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/bin:/usr/sbin:/sbin

     Does this look correct?
 4. Now when I type `sublime` into the terminal I get `command not found`

What am I missing. This is driving me crazy as I fell that I have followed all the steps, but ST3 is still not working for me

     
 


  [1]: https://gist.github.com/artero/1236170

Sublime Text 3 and Terminal prompt for OS X Mavericks?

I had Screen running inside an SSH session.  Terminal froze.  After restarting Terminal, that Screen session still thinks it&#39;s attached.  Maybe it is.  Perhaps I don&#39;t really know what that means.

I&#39;d like to attach to that Screen session from a fresh SSH login.  I do not want to kill that Screen session as important things are happening over there.  : )

The options I think I have ( none of which I know how to solve ):

- How do I detach that Screen session?
- How do I kill the SSH session that that Screen session is attached to?



How do I force detach Screen from another SSH session?

How can I run a shell script and immediately *background* it, however keep the ability to inspect its output any time by tailing `/tmp/output.txt`.

It would be nice if I can *foreground* the process too later.

---
### P.S.  
It would be really cool if you can also show me how to &quot;send&quot; the backgrounded process in to a GNU screen that may or may not have been initialized.

Run a shell script and immediately background it, however keep the ability to inspect its output

How do you check the login tokens for all running jupyter notebook instances?

Example: you have a notebook running in `tmux` or `screen` permanently, and login in remotely through `ssh`. Sometimes, particularly if you&#39;re logging in after a long time, the token is requested again in order to access the notebook session. How do you get hold of the token without having to kill and restart the notebook session with a new token?

Content Type	Original Author	Original Content on Stackoverflow
Question	Vor	View Question on Stackoverflow
Solution 1 - Linux	Anthony	View Answer on Stackoverflow
Solution 2 - Linux	Wei-Yan Lin	View Answer on Stackoverflow
Solution 3 - Linux	galactica	View Answer on Stackoverflow
Solution 4 - Linux	Eduardo Cuomo	View Answer on Stackoverflow
Solution 5 - Linux	Sugan	View Answer on Stackoverflow

How to scroll up and down in sliced "screen" terminal

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

Solution 2 - Linux

Solution 3 - Linux

Solution 4 - Linux

Solution 5 - Linux

Writing outputs to log file and console

How to know if user is logged in with passport.js?

Attributions