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For the Ubuntu 14.04 category

Fix “The Update Information Is Outdated”

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Sometimes, the message “The Update Information Is Outdated” is displayed when you click on a red warning red icon in the status bar. It happened to me last week. This time, it was caused by a Google Chrome update that failed. First, open a terminal (Control + Alt + T) and run the command

sudo apt-get update

If you get an error message related to Google, you can fix it by editing the /etc/apt/sources.list.d/google-chrome.list file. You can do so by issuing the previously opened terminal window

sudo gedit /etc/apt/sources.list.d/google-chrome.list

Make sure that the repository line looks like

deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main

Change the Ubuntu login screen background?

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Changing the login screen background is easy but not obvious. The image file you want to use as the login screen background must have a read access for everyone. Open the image with the Image viewer installed by default. Select the option Set as Wallpaper from the Image menu.

The Appearance option of the Settings will only let you change the desktop background.

How to Install libnfc for PN532 NFC Readers on Linux

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Installing libnfc for PN532 based NFC reader is not exactly as described in the documentation. Some information is scattered in the documentation. This installation guide has been tested with the GO2NFC GO2NFC141U NFC Reader and the Adafruit PN532 NFC/RFID controller breakout board.

1) Install the dependencies:

sudo apt-get install libusb-0.1-4 libusb-dev libpcsclite1 libpcsclite-dev libccid pcscd

2) Create the configuration directory

sudo mkdir -p /etc/nfc/devices.d/

3) Create the file /etc/nfc/devices.d/pn532_uart.conf containing

name = "PN532 board via UART"
connstring = pn532_uart:/dev/ttyACM0
allow_intrusive_scan = true

Replace ttyACM0 with ttyUSB0 if you are using the Adafruit reader.

5) Create the file /etc/nfc/libnfc.conf containing

allow_autoscan = true

6) Download the libnfc library at https://bintray.com/nfc-tools/sources/libnfc. Decompress the archive somewhere. Go into the libnfc-x.x.x directory.

7) Build the library

sudo ./configure --sysconfdir=/etc --prefix=/usr --with-drivers=pn532_uart
sudo make
sudo make install

8) Test your installation. Execute the command utils/nfc-scan-device. You should get an output similar to this one:

nfc-scan-device uses libnfc 1.7.1
1 NFC device(s) found:
- pn532_uart:/dev/ttyACM0:
pn532_uart:/dev/ttyACM0

How To Setup an Internet Gateway using Ubuntu

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Setting up an Internet Gateway using Ubuntu is pretty straight forward. In order to do so, you will need:

  1. A computer with two network interfaces. One hooked to your WAN connection, the other one to your LAN.
  2. The computer needs Ubuntu installed with a minimum of software installed.
  3. Copy the script below to your gateway machine in /etc/network/if-up.d/00-my-gateway. Make sure that the script has the execute permission.
  4. Update the LAN and WAN variables in the script. For example, if eth0 is your WAN interface and eth1 is your LAN interface, then set WAN=eth0 and LAN=eth1.
  5. Reboot.

This script configures the Ubuntu Firewall to forward LAN traffic to the Internet but drops all unsolicited incoming traffic from the Internet. Your network will be stealth. You can use the online tool ShiedlsUP! at https://www.grc.com to test it.


#!/bin/bash

PATH=/usr/sbin:/sbin:/bin:/usr/bin

# Interfaces
LAN=lan
WAN=wan

#
# Delete all existing rules.
#
iptables -F
iptables -t nat -F
iptables -t mangle -F
iptables -X

# Enable routing.
echo 1 > /proc/sys/net/ipv4/ip_forward

# Loopback traffic.
iptables -A INPUT -i lo -j ACCEPT

# Allow established connections.
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -m state --state NEW -i $LAN -j ACCEPT
iptables -A FORWARD -i $WAN -o $LAN -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allow connections from the $LAN to the $WAN.
iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT

# Enable masquerading.
iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE

# No forwarding from the $WAN to the $LAN.
iptables -A FORWARD -i $WAN -o $WAN -j DROP

# Drop everything else from the WAN ... Stealth mode.
iptables -A INPUT -i $WAN -j DROP

Installing memcached to use it with php

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Installing Memcached with php support in Ubuntu is a matter of a few steps:

sudo apt-get install memcached php5-memcached
sudo service apache2 restart

You can test if memcached is active by running this command:
echo "stats settings" | nc localhost 11211
You will end up with a response like this one:

STAT maxbytes 67108864
STAT maxconns 1024
STAT tcpport 11211
STAT udpport 11211
STAT inter 127.0.0.1

STAT item_size_max 1048576
STAT maxconns_fast no
STAT hashpower_init 0
STAT slab_reassign no
STAT slab_automove 0
END

phpMyAdmin session timeout

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phpMyAdmin session timeout is controlled through two parameters. The first one can be found in /etc/php5/apache2/php.ini. It is called session.gc_maxlifetime. The other one can be found in the phpMyAdmin configuration file often named /etc/phpmyadmin/config.inc.php. The name of the parameter is LoginCookieValidity.

The one located in /etc/php5/apache2/php.ini superseeds the one given in /etc/phpmyadmin/config.inc.php if it is smaller.

phpMyAdmin might also have a local php.ini that can override /etc/php5/apache2/php.ini.

Java Applets are no longer working in Linux

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NPAPI support was dropped in Chrome version 35 introduced in Spring 2014. One of the consequences is that Java Applets running with IcedTea no longer works.

Upgrading to Ubuntu 14.04 install the newest version of Chrome. You then lose the ability to run IcedTea in Chrome. The only alternative I have found is using Firefox.

Issues after upgrading to Ubuntu 14.04.1

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After upgrading to Ubuntu 14.04.01, I ran into two issues: One with Apache2 and one with Samba 4.

Apache has been upgraded from 2.2.22 to 2.4.7. The content was no longer accessible. The site configuration directives Order, Allow and Deny such as

Order allow,deny
Allow from all

are now replaced with the Require directive. Detailed information can be found at Apache Module mod_authz_core.

Samba has been upgraded from version 3.6.3 to 4.1.6. The “valid users” behavior changed. It works if the user given in the “force user” directive is listed in the “valid users”. For example, datacloud has to be listed in the “valid users”.

valid users = ctheroux,datacloud
force user = datacloud

How to rename a user in Linux

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Simply issue this command:

usermod -m -d /home/new-account-name -l new-account-name old-account-name

It creates the home directory if it does not exists. It also copy the stuff of the old user into the new user account.

preinst: line 118: a2query: command not found

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If you are getting the following errors while trying to install Apache on Trusty (Ubuntu 14.04), execute the commands below and try to re-install it.


Preparing to unpack .../apache2_2.4.7-1ubuntu4_amd64.deb ...
/var/lib/dpkg/tmp.ci/preinst: line 118: a2query: command not found
dpkg: error processing archive /var/cache/apt/archives/apache2_2.4.7-1ubuntu4_amd64.deb (--unpack):
subprocess new pre-installation script returned error exit status 1
Errors were encountered while processing:
/var/cache/apt/archives/apache2_2.4.7-1ubuntu4_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

The commands to resolve this issue are:

dpkg --fsys-tarfile /var/cache/apt/archives/apache2_2.4.7-1ubuntu4_amd64.deb | tar xOf - ./usr/sbin/a2query > /usr/sbin/a2query

chmod 755 /usr/sbin/a2query

Replace /var/cache/apt/archives/apache2_2.4.7-1ubuntu4_amd64.deb with the name of the file given in the error messages. Note that the first command is splitted on two lines in the above. So, copy both lines at once before pasting it in a terminal window.

How To Restore Skype Status Bar Icon In Ubuntu 14.04

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After installing Skype on Ubuntu 14.04, there is no icon in the status bar. To restore it, simply execute the following command:

sudo apt-get install sni-qt:i386
.

This procedure works on the 64 bits version of Ubuntu.

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