Fixing corrupted GPT backup

When you setup system on a fresh disk you may encounter a problem of corrupted GPT backup. This will happen even more likely when you messed with MBR before on that disk. Free and Open GDISK utility will help you. GDISK will tell you current state of the disk and partition tables, also warn you on possible problems. When you print available partitions (‘p’) and they seem okay, you can simply write out (‘w’) the partition table, that would fix the GPT backup corruption problem :-)

Mac OSX USB installer

In order to create OSX installer on USB memory drive you need to:

  • Download the Mac OSX Yosemite installer from AppStore on you Mac.
  • Create installation media from Terminal by executing following command (remember to adjust YOURUSBVOLUME value):

    sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/YOURUSBVOLUME --applicationpath /Applications/Install\ OS\ X\ Yosemite.app --nointeraction
  • Boot target Mac from USB by pressing ALT/OPTION key while powering-on the computer.
  • Remember to format target drive first with Disk Utility if you want to perform clean installation.

Mac OSX Bluetooth Modem resource busy

In case you wonder why your device does not connect as Modem via Bluetooth to the Mac OSX, or you cannot see COM port on Windows, your mobile device may not simply support or provide DUN (Dial Up Network) and/or SPP (Serial Port Profile) profile.

On Mac OSX I got following error, until I tried another device and/or starting by hand DUN service on a mobile/client machine:

cannot open /dev/cu.Bluetooth-Modem: Resource busy

Notes:

  • Read Bluetooth specification for Serial Port Profile.
  • Read Bluetooth specification for Dial-Up Network Profile.
  • Modern mobile phones / USB 3G dongles, unfortunately, do not provide direct AT/Hayes access to the Radio Modem anymore.
  • You can install DUN application for your smartphone, but it will be only a simple dummy wrapper imitating modem for simple applications, but they do not provide full modem functionality, beware, its a fake.
  • Its only necessary for devices to be paired first in order to get SPP/DUN working. If device does not provide serial port over bluetooth when devices are paired and online, probably its just not there implemented.

OSX 10.10 Yosemite install/runtime problem

If you want to perform a fresh installation of OSX 10.10 Yosemite on an older MacBook(Pro) you can obtain the installer with AppStore and then create the USB installation media.

In case you encounter an Installer Verification Error that prevents you from installing the new system try the following. Its not the system date not bad download as internets says.

This may also help you when encountering problems (i.e. USB Mass Storage) after system upgrade to Yosemite.

Try these boot keyboard shortcuts until you hear boot sound two times:

  • Cmd+Alt+R+P when powering on the Mac (NVRAM Reset)
  • Alt+Ctrl+Shift+PowerON alltogether (SMC Reset)

No problem, you are wolcome :-)

FreeBSD + PPP + GSM/3G/LTE Modem

If you want to use GSM/3G/LTE modem on your FreeBSD box you need to use PPP and following configuration:

default:
 set log Phase Chat LCP IPCP CCP tun command
 ident user-ppp VERSION 
 set device /dev/cuaU0
 set phone *99\#
 set redial 5 10
 set speed 115200
 set dial "ABORT BUSY ABORT NO\sCARRIER TIMEOUT 5 \
           \"\" ATH OK ATZ OK AT OK-AT-OK ATE1Q0 OK \
           AT+CFUN=1 OK-AT-OK \
           AT+CPIN? READY-AT+CPIN=\"1234\"-OK \
           AT+CGDCONT=1,\"ip\",\"internet\" OK \
           \dATDT\T TIMEOUT 40 CONNECT"
 set timeout 10
 enable dns
 set ifaddr 10.0.0.1/0 10.0.0.2/0 255.255.255.255 0.0.0.0
 add default HISADDR

GRUB2 default boot menu entry

Q: How to change the default boot menu entry in GRUB2 used widely on Linux systems?

A: You can do it easily as root in three following steps:

  1. Run update-grub program and copy entry name that you want to make default.
  2. Edit /etc/default/grub and add or modify existing GRUB_DEFAULT="your_menu_entry_here".
  3. Run update-grub program again to update the grub bootloader configuration.

Screenshots in Android 4

If you wonder where did the power menu option to make a screenshot go in Android 4 – you need to long press Power + Volume Down buttons together :-)

Still I don’t know how to disable screen inside ongoing call when my Power button is assigned to end call, or how to end call when screen is locked and Power button is assigned to lock screen ;-) Design Fail or hidden solution somewhere there deep inside..? Apple simply use one button to end/diall call and separate mechanical switch to lock the device – simple functional and elegant.. but hey why Android does not use this solution as well, is “button switch pair” already patented by Apple? ;-)

YouTube and HTML5

I have found very simple solution on how to access YouTube videos that require Flash using HTML5 player. Although front site may not support HTML5 video player, YouTube usually allows to embed videos to other sites, they also should use WebM codec developed by Google. If you have a video that does not work in HTML5 by default try to run it in embed player by URL modification – replace “/watch?v=” with “/embed/” and it should work! :-)

Example: http://www.youtube.com/watch?v=M84Y6VXAIaU -> http://www.youtube.com/embed/M84Y6VXAIaU