UNetbootin

The best software to create bootable USB drives/sticks: UNetbootin

Cross-platform, I discovered that after finding out that Ubuntu 14.04 LTS "Startup Disk Creator" was not getting the job done.

Under Debian: $ sudo apt-get install unetbootin

MySQL quick setup reference

MySQL quick setup reference

$ mysql -u root -p
> CREATE DATABASE some_db;
> CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'clear-text-password';
> GRANT ALL PRIVILEGES ON some_db.* TO 'newuser'@'localhost';
> FLUSH PRIVILEGES;
> quit

Note: before going to production, it's always a good idea to run:

$ sudo mysql_secure_installation

This will make you review some less secure MySQL default setings

Using Android Virtual Device (AVD) Emulator on Linux

Scenario: under Linux, setup Android SDK, to be able to use an AVD (android virtual device) to test any given .apk - without using an IDE like Eclipe.

Preparing the system

# cd /opt (or any preferred install directory)
# wget ADT_DOWNLOAD_LINK
# unzip ADT_VERSION.zip
# chown -R your_user.your_user adt-bundle-linux-SYSTEM-VERSION

# ln -sf /opt/adt-bundle-linux-SYSTEM-VERSION/sdk/platform-tools/adb /usr/local/bin/adb
# ln -sf /opt/adt-bundle-linux-SYSTEM-VERSION/sdk/tools/emulator /usr/local/bin/emulator
# ln -sf /opt/adt-bundle-linux-SYSTEM-VERSION/sdk/tools/android /usr/local/bin/android


Using SDK GUI


$ android
will open SDK manager - use it if you want to install additional packages, including other targets/android versions for AVDs.

$ android avd
will open virtual devices manager - use to create/define/remove AVDs


Note 1
One may face difficulties to add specific brand emulators (ex: Samsung Galaxy S, Galaxy Tab, etc); you'll need to:
a) SDK manager > tools > manage add-on sites > user defined sites > new
OR
b) unzip/uncompress a downloaded add-on package in a new directory under sdk/add-ons/
(ref: http://developer.samsung.com/android/tools-sdks/Samsung-GALAXY-Tab-Emulator)


Note 2
AVDs do not support WiFi emulated connections, only 3G - so if you need to test i.e. a different behavior, likely your only option is to use a real/physical device
(ref: http://stackoverflow.com/questions/7876302/enabling-wifi-on-android-emulator)


Note 3
AppInventor 2 requires WiFi to work with the "MIT AI2 Companion" app (that syncronizes AppInventor with a device)


Note 4
By Jan/2014 AI2 doesn't support emulators under Linux, but to test your AppInventor .apk on an AVD, you can:
$ adb install your_package.apk (1st time)
$ adb install -r your_package.apk (when reinstalling)


Refs:
http://developer.android.com/tools/devices/managing-avds-cmdline.html
http://developer.android.com/tools/devices/emulator.html

Cloning a VirtualBox machine running CentOS

Link: Cloning a VirtualBox machine running CentOS causes network interfaces to fail

Protecting VBox Virtual Networks

Be careful in a host having "ip_forwarding" (routing) kernel option enabled. Consider aways set iptables "filter" (firewall) rules. Setting up just iptables "masquarade" (nat) may allow access from outside.

$ sudo su -

# vi /etc/iptables_FW_rules
*filter
#
# Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT
-A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT
#
# Accepts all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Accepts all established routed connections
-A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
#
# VIRTUALBOX VIRTUAL NETWORKS PROTECTION
# vboxnetX is created by type "host-only network" on VBox Manager
-A FORWARD -i eth+ -o vboxnet+ -j REJECT
-A FORWARD -i wlan+ -o vboxnet+ -j REJECT
# allow VMs access outside
-A FORWARD -i vboxnet+ -o eth+ -j ACCEPT
-A FORWARD -i vboxnet+ -o wlan+ -j ACCEPT
#
# Allows all outbound traffic
# You may want to modify this to only allow certain traffic
-A OUTPUT -j ACCEPT
#
# Allow ping request to host
-A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT
#
# log host denied calls (access via 'dmesg' command)
#-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7
#
# Reject all other inbound - default deny unless explicitly allowed policy:
-A INPUT -j REJECT
-A FORWARD -j REJECT
COMMIT


# vi /etc/init.d/iptables-on-boot.sh
#!/bin/sh
/sbin/iptables-restore < /etc/iptables_FW_rules


# chmod ug+x /etc/init.d/iptables-on-boot.sh


# runlevel


# ln -s /etc/init.d/iptables-on-boot.sh /etc/rc2.d/S30iptables-on-boot



---- useful commands ---

Flush (clear) rules to test:
# iptables -F (flush default type filter/FW rules)
# iptables -t nat -F (flush masquerade/NAT rules)

For a complete report on iptables rules:

# iptables -L -v -n
# iptables -t nat -L -v -n

VBox Virtual Networks Quick Guide

While I'm writing this post, VirtualBox 4.3.4 "NAT networks" (Network Address Translation Service) don't work properly (still experimental), so to have an internal network where VMs are accessible by Host but NOT from outside, and VMs are able to access networks outside host (as internet), I had to:

1) on Host VirtualBox Manager > file > preferences >  network > host-only networks > add; on the (guest) VM settings > network > attached to > host-only adapter > set proper name

2) on Host, enable routing on the kernel:
$ sudo vi /etc/sysctl.conf
uncomment "net.ipv4.ip_forward=1"

3) on Host, enable NAT outside:
$ sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
$ sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE

To make it persistent under a Debian/Linux Mint host, create a new ifup rule:

$ sudo vi /etc/network/if-up.d/iptables_NAT_vboxnet_out

#!/bin/sh
#
# Don't bother to do anything for lo or VBoxNets.
IFTYPE=$(echo "$IFACE" | cut -c1-2)
if [ "$IFTYPE" = lo -o "$IFTYPE" = vb ]; then
    exit 0
fi
# Only run from ifup.
if [ "$MODE" != start ]; then
    exit 0
    else
    iptables -t nat -A POSTROUTING -o "$IFACE" -j MASQUERADE
fi

$ sudo chmod ugo+x /etc/network/if-up.d/iptables_NAT_vboxnet_out

Reestart the Host to test.

Installing VirtualBox (Bin Package)

Go to

https://www.virtualbox.org/wiki/Linux_Downloads

download "All distributions" (runs a bin installer)

$ sudo sh VirtualBox-VERSION-SYSTEM.run

After installing, go to https://www.virtualbox.org/wiki/Downloads

then click on "VirtualBox 4.3.2 Oracle VM VirtualBox Extension Pack"

choose open download directly on VirtualBox


To make VM fit on host screen etc:
running VM > devices > insert guest additions cd image
execute cd installer via SO


To update/upgrade VirtualBox, just make the same process; you'll need to reinstall Extension Pack