Category Archives: unsorted

I spent a lot of hours before realizing that Ubuntu 14.04 blocks tcp by default.

One can check this by

ps aux | grep X
root      1127  0.1  3.4 364380 71748 tty7     Ss+  12:08   0:00 /usr/bin/X -core :0 
   -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch

Notice the -nolisten option in output.

To enable it, add xserver-allow-tcp=true to lightdm:

sudo vi /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf

 [SeatDefaults]
 # Dump core
 xserver-command=X -core
 xserver-allow-tcp=true

Restart X (or reboot) and forward X11 desktop by launching:

# server
export DISPLAY=<your-localhost-ip>:0

# client
xhost +

You can test Display forwarding by launching on server

xeyes

credits

Install Trac

# install trac package from Ubuntu repo
sudo apt-get install trac

# init the project files
sudo mkdir -p /var/trac/myproject
cd /var/trac/myproject
sudo trac-admin . initenv

# basic authentication
sudo apt-get install apache2-utils
sudo htpasswd -c .htpasswd adminusername
sudo trac-admin . permission add adminusername TRAC_ADMIN

# folder permissions
sudo chown -R www-data: .
sudo chmod -R 775 .

cp wsgi_trac.py -> /var/trac/myproject/

import os
import sys
import trac.web.main
sys.stdout=sys.stderr
os.environ['TRAC_ENV'] = '/var/trac/myproject'
application = trac.web.main.dispatch_request

cp to /etc/nginx/sites-enabled/trac.conf or add to /etc/nginx/nginx.conf

server {
  listen  80;
  server_name  trac.local;

  location / {
    auth_basic_user_file /var/trac/myproject/.htpasswd;
    auth_basic 'this is not for you';
    uwsgi_param REMOTE_USER $remote_user;

    include  uwsgi_params;
    uwsgi_pass  127.0.0.1:5544;
  }
}

cp trac_uwsgi.ini -> /etc/uwsgi/apps-enabled/

[uwsgi]
uid=trac
gid=tracsys
chmod-socket=777
chown-socket=trac
chdir = /var/trac/myproject
socket = 127.0.0.1:5544
module = wsgi_trac:application
processes = 2
master = 1

restart the services

sudo service nginx restart && sudo service uwsgi restart

Credits: dev-smart, habrahabr.

P.S. Don’t forget about Nginx uwsgi_param REMOTE_USER for authentication to work.
I spent a lot of nerves fixing Trac Error: Authentication information not available 🙂

Add at the beginning of /etc/rsyslog.d/50-default.conf:

$template PerHostLog,"/var/log/filename.log"
if $fromhost-ip != ’127.0.0.1′ then -?PerHostLog
& ~

Uncomment the lines in /etc/rsyslog.conf:

$ModLoad imudp
$UDPServerRun 514
$ModLoad imtcp
$InputTCPServerRun 514

Restart the service

sudo service rsyslog restart

Don’t forget to tune the permissions:

sudo chown syslog:syslog /var/log

This method is generally used if you are targeting a specific output file size and output quality from frame to frame is of less importance. This is best explained with an example. Your video is 10 minutes (600 seconds) long and an output of 50 MB is desired. Since bitrate = file size / duration:
(50 MB * 8192 [converts MB to kilobits]) / 600 seconds = ~683 kilobits/s total bitrate
683k – 128k (desired audio bitrate) = 555k video bitrate

avconv -y -i video.mkv -c:v libx264 -preset medium -b:v 555k -pass 1 -an -sn -f matroska /dev/null && \
avconv -i video.mkv -c:v libx264 -preset medium -b:v 555k -pass 2 -c:a libmp3lame -ac 2 -b:a 128k \ 
 -c:s copy -map 0:0 -map 0:1 -map 0:2 -map 0:3 video_out.mkv

• “Vanilla” JavaScript (without jQuery)

  sendPost = function(url, data) {
      var xmlhttp = new XMLHttpRequest();
      var params = serialize(data);
  
      xmlhttp.open("POST", url, true);
      xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
      xmlhttp.setRequestHeader("Content-length", params.length);
      xmlhttp.setRequestHeader("Connection", "close");
  
      xmlhttp.send(params);
  
      xmlhttp.onreadystatechange = function() {
          if (xmlhttp.readyState === 4 && xmlhttp.status === 200){
              console.log(xmlhttp.responseText);
          }
      };
  }
  
  serialize = function(obj, prefix) {
      var str = [];
      for(var p in obj) {
          var k = prefix ? prefix + "[" + p + "]" : p, v = obj[p];
          str.push(typeof v == "object" ?
                  serialize(v, k) :
                  encodeURIComponent(k) + "=" + encodeURIComponent(v));
      }
      return str.join("&");
  }
  
  sendPost("http://some/host", {login: 'me@abc.def', password: 'mypassword'});
  

• Or just use curl:

  curl 'http://some/host' --data 'login=me%40abc.def&password=mypassword'
  

In the next example, mongoimport takes data passed to it on standard input (i.e. with a | pipe.)
Without the output specification (i.e. “-o collection.json”), mongoexport writes output to standard output (i.e. “stdout”).

mongoexport -d dbname -c colname | gzip > dump.txt.gz
zcat dump.txt.gz | mongoimport -d dbname -c colname

В консоли браузера:

GALLERY_DATA.images[0].urls['full'];

Массовые действия:

for(var i=0;i<50;i++){
    var win=window.open(
        GALLERY_DATA.images[i].urls['full'], '_blank'
    );
    win.focus();
}

Ссылка на сегодняшний день следующего вида:

https://files.geometria.ru/pics/original_hd/034/236/34236256.jpg?st=mUdcSH2treKdvMqsi2smUA&e=1388179689

034/236 – id альбома
34236256 – id фото
st, e – уникальные параметры для каждой фотографии