Ubuntu these days comes with [UFW - Uncomplicated Firewall][1]. UFW is an easy-to-use method of handling iptables rules.

Try using this command to allow a port:

    sudo ufw allow 1701

To test connectivity, you could try shutting down the VPN software (freeing up the ports) and using [netcat][2] to listen, like this:

    nc -l 1701

Then use telnet from your Windows host and see what shows up on your Ubuntu terminal. This can be repeated for each port you&#39;d like to test.

  [1]: https://help.ubuntu.com/community/UFW
  [2]: https://en.wikipedia.org/wiki/Netcat




If you want to open it for a range and for a protocol 

    ufw allow 11200:11299/tcp
    ufw allow 11200:11299/udp


This is weird.  This is what happens at the JavaScript console in Chrome (version 42.0.2311.135, 64-bit).

&lt;!-- language: lang-none --&gt;

    &gt; 0
    &lt; 0
    &gt; 00
    &lt; 0
    &gt; 0.0
    &lt; 0
    &gt; 00.0
    X Uncaught &gt; SyntaxError: Unexpected number

Firefox 37.0.2 does the same, although its error message is:

&lt;!-- language: lang-none --&gt;

    SyntaxError: missing ; before statement

There&#39;s probably some technical explanation regarding the way JavaScript parses numbers, and perhaps it can only happen when tinkering at the console prompt, but it still seems wrong.

Why does it do that?


Why does 00.0 cause a syntax error?

When commiting files using VSCode&#39;s Git integration, is there any way of writing a multiline commit message, or am I limited to a single line only? 

As of now, VSCode is great at staging files. But it seems I&#39;ll still have to write most of my commit messages from the terminal.

Multiline git commit message in VSCode

I know a little about Linux. Today I created a [VPN][1] server on my Ubuntu installation according to *[Set up a simple IPsec/L2TP VPN server for Ubuntu, Arch Linux and Debian][2]*.

But when I finish the installation, I use my iPhone to connect the [IPsec][3] VPN, bur it shows the VPN Server has no response.

The GitHub document shows

&gt; Ports 1701, 500 and 4500 must be opened for the VPN to work!

So I have tried to open these ports on my Ubuntu server.

I use the [iptables][4] command to open these ports, but it failed. Maybe I don&#39;t known how to use this command correctly. How can I open these ports on my Ubuntu server?

And if these ports have been opened successfully, can it be proved by the Windows [CMD][5] window through [telnet][6]&#39;ting the port?


  [1]: https://en.wikipedia.org/wiki/Virtual_private_network
  [2]: https://github.com/philplckthun/setup-simple-ipsec-l2tp-vpn
  [3]: https://en.wikipedia.org/wiki/IPsec
  [4]: https://en.wikipedia.org/wiki/Iptables
  [5]: https://en.wikipedia.org/wiki/Cmd.exe
  [6]: https://en.wikipedia.org/wiki/Telnet







How can I open some ports on Ubuntu?

I know a little about Linux. Today I created a <a href="https://en.wikipedia.org/wiki/Virtual_private_network" target="_blank" rel="noopener noreferrer">VPN</a> server on my Ubuntu installation according to <a href="https://github.com/philplckthun/setup-simple-ipsec-l2tp-vpn" target="_blank" rel="noopener noreferrer">Set up a simple IPsec/L2TP VPN server for Ubuntu, Arch Linux and Debian</a>.
But when I finish the installation, I use my iPhone to connect the <a href="https://en.wikipedia.org/wiki/IPsec" target="_blank" rel="noopener noreferrer">IPsec</a> VPN, bur it shows the VPN Server has no response.
The GitHub document shows
> Ports 1701, 500 and 4500 must be opened for the VPN to work!
So I have tried to open these ports on my Ubuntu server.
I use the <a href="https://en.wikipedia.org/wiki/Iptables" target="_blank" rel="noopener noreferrer">iptables</a> command to open these ports, but it failed. Maybe I don't known how to use this command correctly. How can I open these ports on my Ubuntu server?
And if these ports have been opened successfully, can it be proved by the Windows <a href="https://en.wikipedia.org/wiki/Cmd.exe" target="_blank" rel="noopener noreferrer">CMD</a> window through <a href="https://en.wikipedia.org/wiki/Telnet" target="_blank" rel="noopener noreferrer">telnet</a>'ting the port?

I need to run a `CRON` job every 10 seconds from started time.

In Linux how to run a `CRON` job on every 10 seconds from the time its started? 

I am trying to solve that as following: **when I make a request (or start) at 04:28:34 it should start at 04:28:44 not at 4:28:40**

This is what I have done
```
# m h  dom mon dow   command
*/10 * * * * /usr/bin/wget http://api.us/application/
```
What did I do wrong? Why does this not trigger `wget` every 10 seconds?

How to setup CRON job to run every 10 seconds in Linux?

I just started setting up a centos server today and noticed that the default version of python on centos is set to 2.6.6. I want to use python 2.7 instead. I googled around and found that 2.6.6 is used by system tools such as YUM so I should not tamper with it. Then I opened up a terminal on my mac and found that I had python 2.6.8 and 2.7.5 and 3.3.3 installed. Sorry for the long story. In short I just want to know how to lookup all the version of python installed on centos so I don&#39;t accidentally install it twice.

How to check all versions of python installed on osx and centos

I&#39;ve just installed [Linux Mint][1] 17 and faced a problem that I couldn&#39;t use the Russian language in the terminal. (I see `?` instead of letters.)

On one forum I found this solution:

&gt; Added in ~/.profile:

    export LANG=ru_RU.UTF-8
    export LC_CTYPE=ru_RU.UTF-8
    export LC_ALL=ru_RU.UTF-8

It helped, but also changed my interface language to Russian (which I didn&#39;t want). That&#39;s not even a problem, but anyway, I would like to know, how this code works (every line).

  [1]: https://en.wikipedia.org/wiki/Linux_Mint







Explain the effects of export LANG, LC_CTYPE, and LC_ALL

I understand I can use `find . -name &quot;.DS_Store&quot;` to [find all the .DS_Store files][1]  in the current folder and all subfolders. But how could I delete them from command line simultaneously? I found it&#39;s really annoying to switch back and forth to all folders and delete it one by one.

  [1]: https://stackoverflow.com/questions/5905054/how-can-i-recursively-find-all-files-in-current-and-subfolders-based-on-wildcard

Delete .DS_STORE files in current folder and all subfolders from command line on Mac

Is it possible to copy text from a file, opened with `nano`, to the shell?

I have a text file, and I want to copy several lines to the console, but I cannot find a keyboard shortcut to copy the text.

Copy text from nano editor to shell

Ubuntu apt-get unable to fetch packages

I just tried out Docker. It is awesome but seems not work nicely with ufw. By default, docker will manipulate the iptables a little bit. The outcome is not a bug but not what I expected.
For more details you can read [The dangers of UFW + Docker][1]

My goal is to set up a system like

        Host (running ufw) -&gt; docker container 1 - nginx (as a reverse proxy)
                           -&gt; docker container 2 - node web 1
                           -&gt; docker container 3 - node web 2
                           -&gt; .......
I want to manage the incoming traffic (e.g. restrict access) through ufw therefore I don&#39;t want docker to touch my iptables. Here is my test

**Environment:**

- a newly installed Ubuntu 14.04 (kernel: 3.13.0-53 )
- Docker 1.6.2 
- ufw forwarding is enabled.( [Enable UFW forwarding] [2] )
- `--iptables=false` was added to the Docker daemon.


**First Attempt**

    docker run --name ghost -v /home/xxxx/ghost_content:/var/lib/ghost -d ghost
    docker run --name nginx -p 80:80 -v /home/xxxx/nginx_site_enable:/etc/nginx/conf.d:ro --link ghost:ghost -d nginx

No luck. The first command is fine but the second command will throw an error

    Error response from daemon: Cannot start container

**Second Attempt**

Then I found this: [unable to link containers with --iptables=false #12701][3]

After running the following command, everything looks OK.

    sudo iptables -N DOCKER

However, I noticed that I can not establish any outbound connections inside containers. For example:

    xxxxg@ubuntu:~$ sudo docker exec -t -i nginx /bin/bash
    root@b0d33f22d3f4:/# ping 74.125.21.147
    PING 74.125.21.147 (74.125.21.147): 56 data bytes
    ^C--- 74.125.21.147 ping statistics ---
    35 packets transmitted, 0 packets received, 100% packet loss
    root@b0d33f22d3f4:/# 

If I remove `--iptables=false` from the Docker daemon, then the internet connection of containers will be back to normal but the ufw will not work &#39;properly&#39;  (well...by my definition).

So, what is the best practice of docker + ufw? Can anyone provide some help?

  [1]: http://blog.viktorpetersson.com/post/101707677489/the-dangers-of-ufw-docker
  [2]: https://docs.docker.com/installation/ubuntulinux/#enable-ufw-forwarding &quot;Enable UFW forwarding&quot;
  [3]: https://github.com/docker/docker/issues/12701

What is the best practice of docker + ufw under Ubuntu

I&#39;m trying to install package with pip on Ubuntu server:

    $ pip install MySQLdb
    Downloading/unpacking MySQLdb
    Killed

And it&#39;s getting killed. There is enough free RAM on server. Why it is killed?

UPD
Logs:

&gt; Out of memory: Kill process 6627 (pip) score 297 or sacrifice child

Thats strange, because I have about 150 mb free RAM.

pip install - killed

I installed docker on a Debian 7 machine in the following way 

    $ echo deb http://get.docker.io/ubuntu docker main &gt; /etc/apt/sources.list.d/docker.list
    $ sudo apt-get update
    $ curl -sSL https://get.docker.com/ubuntu/ | sudo sh

After that when I first tried creating an Image it failed with the following error


     time=&quot;2015-06-02T14:26:37-04:00&quot; level=info msg=&quot;[8] System error: write /sys/fs/cgroup/docker/01f5670fbee1f6687f58f3a943b1e1bdaec2630197fa4da1b19cc3db7e3d3883/cgroup.procs: no space left on device&quot;

Here is the docker info 

    Containers: 2
    Images: 21
    Storage Driver: aufs
    Root Dir: /var/lib/docker/aufs
    Backing Filesystem: extfs
    Dirs: 25
    Dirperm1 Supported: true
    Execution Driver: native-0.2
    Kernel Version: 3.16.0-0.bpo.4-amd64
    Operating System: Debian GNU/Linux 7 (wheezy)
    CPUs: 2
     Total Memory: 15.7 GiB
   
    
    WARNING: No memory limit support
     WARNING: No swap limit support


How can I increase the memory? Where are the system configurations stored?

From Kal&#39;s suggestions:

When I got rid of all the images and containers it did free some space and the image build ran longer before failing with the same error. So the question is, which space is this referring to and how do I configure it?




Docker error : no space left on device

I have a spring boot application (using embedded tomcat 7), and I&#39;ve set `server.port = 0` in my `application.properties` so I can have a random port.  After the server is booted up and running on a port, I need to be able to get the port that that was chosen.

I cannot use `@Value(&quot;$server.port&quot;)` because it&#39;s zero.  This is a seemingly simple piece of information, so why can&#39;t I access it from my java code?  How can I access it?  



Spring Boot - How to get the running port

I&#39;m trying to run a container but I get the following issue :

    Error response from daemon: Cannot start container b005715c40ea7d5821b15c44f5b7f902d4b39da7c83468f3e5d7c042e5fe3fbd: iptables failed: iptables --wait -t filter -A DOCKER ! -i docker0 -o docker0 -p tcp -d 172.17.0.43 --dport 80 -j ACCEPT: iptables: No chain/target/match by that name.
     (exit status 1)

Here is the command I use :

    docker run -d -p 10080:80 -v /srv/http/website/data:/srv/http/www/data -v /srv/http/website/logs:/srv/http/www/logs myimage

Isn&#39;t opening port 80 on my server enough? Is there something I missed with docker interface?
I use iptables with a script like this :

    #!/bin/sh
    
    # reset :
    iptables -t filter -F
    iptables -t filter -X
    
    # Block all :
    iptables -t filter -P INPUT DROP
    iptables -t filter -P FORWARD DROP
    iptables -t filter -P OUTPUT DROP
    
    # Authorize already established connections :
    iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
    iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
    
    # Authorize backloop :
    iptables -t filter -A INPUT -i lo -j ACCEPT
    iptables -t filter -A OUTPUT -o lo -j ACCEPT
    
    # Authorize ssh :
    iptables -t filter -A INPUT -p tcp --dport 22 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 22 -j ACCEPT
    
    # Authorize HTTP :
    iptables -t filter -A INPUT -p tcp --dport 80 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 80 -j ACCEPT
    
    # Authorize HTTPS :
    iptables -t filter -A INPUT -p tcp --dport 443 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 443 -j ACCEPT
    
    # Authorize DNS :
    iptables -t filter -A INPUT -p tcp --dport 53 -j ACCEPT
    iptables -t filter -A OUTPUT -p udp --dport 53 -j ACCEPT
    iptables -t filter -A INPUT -p udp --dport 53 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 53 -j ACCEPT
    
    # Ping :
    iptables -t filter -A INPUT -p icmp -j ACCEPT
    iptables -t filter -A OUTPUT -p icmp -j ACCEPT
    
    # Authorize FTP :
    iptables -t filter -A INPUT -p tcp --dport 20 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 20 -j ACCEPT
    iptables -t filter -A INPUT -p tcp --dport 21 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 21 -j ACCEPT
    
    # # Authorize NTP :
    # iptables -t filter -A INPUT -p udp --dport 123 -j ACCEPT
    # iptables -t filter -A OUTPUT -p udp --dport 123 -j ACCEPT
    
    # Authorize IRC :
    iptables -t filter -A INPUT -p tcp --dport 6667 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 6667 -j ACCEPT
    
    # Authorize port 10000 (for Node.JS server) :
    iptables -t filter -A INPUT -p tcp --dport 10000 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 10000 -j ACCEPT
    
    # Authorize port 631 (Cups server) :
    iptables -t filter -A INPUT -p tcp --dport 631 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 631 -j ACCEPT
    
    # Authorize port 9418 (git) :
    iptables -t filter -A INPUT -p tcp --dport 9418 -j ACCEPT
    iptables -t filter -A OUTPUT -p tcp --dport 9418 -j ACCEPT

How could I fix this?

Running docker container : iptables: No chain/target/match by that name

I started redis server on ubuntu by typing this on terminal: $redis-server

This results in following &gt; http://paste.ubuntu.com/12688632/

    aruns ~ $ redis-server
    27851:C 05 Oct 15:16:17.955 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
    27851:M 05 Oct 15:16:17.957 # You requested maxclients of 10000 requiring at least 10032 max file descriptors.
    27851:M 05 Oct 15:16:17.957 # Server can&#39;t set maximum open files to 10032 because of OS error: Operation not permitted.
    27851:M 05 Oct 15:16:17.958 # Current maximum open files is 4096. maxclients has been reduced to 4064 to compensate for low ulimit. If you need higher maxclients increase &#39;ulimit -n&#39;.
    27851:M 05 Oct 15:16:17.958 # Creating Server TCP listening socket *:6379: bind: Address already in use

How can I fix this problem, it there any manual or automated process to fix this binding.

redis-server in ubuntu14.04: Bind address already in use

I set up a simple Node server in Docker.

**Dockerfile**

    FROM node:latest
    RUN apt-get -y update
    ADD example.js .
    EXPOSE 1337   
    CMD node example.js

**example.js**

&lt;!-- language: javascript --&gt;

    var http = require(&#39;http&#39;);
    http.createServer(function (req, res) {
      res.writeHead(200, {&#39;Content-Type&#39;: &#39;text/plain&#39;});
      res.end(&#39;Hello World\n&#39;+new Date);
    }).listen(1337, &#39;127.0.0.1&#39;);
    console.log(&#39;Server running at http://127.0.0.1:1337/&#39;);

Now build the image

    $ docker build -t node_server .

Now run in container

    $ docker run -p 1337:1337 -d node_server  
    $ 5909e87302ab7520884060437e19ef543ffafc568419c04630abffe6ff731f70

Verify the container is running and ports are mapped:

    $ docker ps  

    CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                    NAMES
    5909e87302ab        node_server         &quot;/bin/sh -c &#39;node exa&quot;   7 seconds ago       Up 6 seconds        0.0.0.0:1337-&gt;1337/tcp   grave_goldberg

Now let&#39;s attach to the container and verify the server is running inside:

    $ docker exec -it 5909e87302ab7520884060437e19ef543ffafc568419c04630abffe6ff731f70 /bin/bash 

And in the container command line type:

    root@5909e87302ab:/# curl http://localhost:1337
    Hello World
    Mon Feb 15 2016 16:28:38 GMT+0000 (UTC)

Looks good right?

**The problem**

When I execute the same curl command on the host (or navigate with my browser to http://localhost:1337) I see nothing.

Any idea why the port mapping between container and host doesn&#39;t work?

Things I already tried:

 - Running with the `--expose 1337` flag

Containerized Node server inaccessible with server.listen(port, &#39;127.0.0.1&#39;)

I have PostgreSQL 9.3 installed on a server running Ubuntu Server 14.04.

If I ssh into the server via terminal, I&#39;m able to connect with psql. But when I try to configure pgAdmin III to do the remote connection, I get:

&gt; Server doesn&#39;t listen The server doesn&#39;t accept connections: the
&gt; connection library reports  could not connect to server: Connection
&gt; refused Is the server running on host &quot;172.24.3.147&quot; and accepting
&gt; TCP/IP connections on port 5432?

When I run on the server `service postgresql status` it gives me:

    9.3/main (port 5432): online

So of course I&#39;m missing something important here.

EDIT

When running `netstat -na` on the server, I get (relevant portion, I guess):

    Active Internet connections (servers and established)
    Proto Recv-Q Send-Q Local Address           Foreign Address         State      
    tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN     
    tcp        0      0 127.0.0.1:5432          0.0.0.0:*               LISTEN     
    tcp        0      0 172.24.3.147:22         172.24.3.240:61950      ESTABLISHED
    tcp        0      0 172.24.3.147:22         172.24.3.240:60214      ESTABLISHED



Content Type	Original Author	Original Content on Stackoverflow
Question	elsonwx	View Question on Stackoverflow
Solution 1 - Linux	shane	View Answer on Stackoverflow
Solution 2 - Linux	Sanjeev Rohila	View Answer on Stackoverflow

How can I open some ports on Ubuntu?

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

Solution 2 - Linux

Multiline git commit message in VSCode

Why does 00.0 cause a syntax error?

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