finding ip ranges via ASN

To obtain all the IP ranges of an ISP or large organization, got a procedure from this quora post -

https://www.quora.com/How-can-I-obtain-a-list-of-IP-addresses-owned-by-a-specific-company-I-would-like-to-provide-a-targeted-offer-to-site-visitors-if-they-work-at-a-certain-company-I-would-like-to-get-a-list-of-the-IP-addresses-that-this-organization-owns


https://www.peeringdb.com/net/1903 has Airtel's ASN.

Then, we can use that ASN in this whois query -

whois -h whois.radb.net -- '-i origin AS9498' | grep -Eo "([0-9.]+){4}/[0-9]+" > airtel.txt
whois -h whois.radb.net -- '-i origin AS9829' | grep -Eo "([0-9.]+){4}/[0-9]+" > bsnl.txt

boot from grub - link dump

https://www.linuxquestions.org/questions/linux-software-2/booting-windows-from-the-grub-prompt-275446/

root (hd0,0)
makeactive
chainloader --force +1
boot

But grub 2 is different.
https://www.linux.com/learn/how-rescue-non-booting-grub-2-Linux

grub> set root=(hd0,1)
grub> linux /vmlinuz root=/dev/sda1
grub> initrd /initrd.img
grub> boot

https://unix.stackexchange.com/questions/77263/use-grub-rescue-to-boot-from-windows-xp-partition-cd-or-usb

set prefix=(hd1,1)/grub
set root=(hd1,1)
insmod normal
normal

https://www.aioboot.com/en/boot-windows-grub2/

from grub rescue prompt,
search -s root -f /NTDETECT.COM
drivemap -s hd0 $root
ntldr /ntldr
boot

https://www.gnu.org/software/grub/manual/grub/grub.html#DOS_002fWindows

parttool (hd0,1) hidden-
parttool (hd0,2) hidden+
set root=(hd0,1)
chainloader +1
parttool ${root} boot+
boot

https://www.aioboot.com/en/boot-windows-grub2/

http://forums.justlinux.com/showthread.php?153121-Fun-with-GPT-partitioning

unable to make XP boot from a cloned volume on Intel Mac

Just a few lines of notes - trying making other partitions hidden to make XP boot - doesn't work, since partition is GPT, grub says hidden - unknown argument or whatever.

using dd to clone a usb drive

From
https://www.garron.me/en/bits/convert-store-copy-bootable-usb-iso-file-another-usb.html

• use df to find the device name, then
• dd if=/src/dev/path of=/dest/dev/path conv=notrunc
  for example dest can be a file also - 
  dd if=/dev/sdc of=/home/user/backup-usb.dd conv=notrunc
  
  (notrunc is useful only when writing to a file, https://stackoverflow.com/questions/20526198/why-using-conv-notrunc-when-cloning-a-disk-with-dd )

Linux Mint 18.1 not booting - solved

Linux Mint was not booting into graphical mode. It was not even dropping me into an emergency shell - a dialog box about not being able to connect to upstart would appear, your session lasted only 10 seconds etc, and the window manager would restart. Initially I thought this was due to some problem related to booting as in my previous post. But then, saw this post on the Linux Mint forums. So, hit Ctrl Alt F2 to get a shell, (in my case, fn+Ctrl+Option, since this is a Macbook), did
  apt remove virtualbox-guest*
and rebooted OK. 

link dump - ALSA etc - for software lock-in amplifier

ALSA tutorial for beginners - 2004 - http://www.linuxjournal.com/article/6735?page=0,1

PortAudio - http://www.portaudio.com/

ALSA example
https://gist.github.com/albanpeignier/104902

Another ALSA tutorial - http://equalarea.com/paul/alsa-audio.html

Checking the code and compiling from https://www.av8n.com/physics/lockin.htm

http://www.qtcentre.org/threads/53452-QtGui-QApplication-No-such-file-or-directorty

QApplication and Qwidgets derived classes are in widgets module in Qt 5 so to fix that you need to add QT += widgets in the .pro file and run qmake and also use #include <QApplication> instead of #include <QtGui/QApplication> (and the code becomes compatible with both Qt 4 and 5), you can read more here

Or download 10.04,

and
https://help.ubuntu.com/community/Installation/FromUSBStick#Install_and_run_Startup_Disk_Creator_alias_usb-creator

link dump for triple boot of Windows, Linux and MacOS on Macbook

1. https://lifehacker.com/how-to-run-a-portable-version-of-windows-from-a-usb-dri-1565509124

https://medium.com/@manujarvinen/setting-up-a-multi-boot-of-5-linux-distributions-ca1fcf8d502

2. Brief notes: Using rEFInd, need to allow drive to spin up for it to be visible on refind.

usb drive not seen with refind.

Windows XP installer did not allow installation to partition which was created after the mac partition, so creating a new partition by moving the mac partition - 8 hours!

3. EFI fix - https://apple.stackexchange.com/questions/57597/how-to-fix-broken-efi-partition

https://www.kubuntuforums.net/showthread.php/43221-GRUB-2-A-Guide-for-Users/page15?p=379352#post379352

Tried gdisk -> Advanced -> H

Finally. Install Mint alongside other partitions.

4. https://www.tecmint.com/command-line-tools-to-monitor-linux-performance/

5. EFI - Created with Linux mint install graphical using 200 MB at beginning.

Edit: 7 Nov 2019 - https://www.intowindows.com/how-to-create-live-usbcddvd-of-vistaxp/

Edit: 2 Jan 2021 - Possibly a portable Win10 using WintoUSB may be the easiest option, for Windows 7 and higher versions of Windows - the Macbook is supposed to boot from CD if we press and hold the C key. https://en.wikipedia.org/wiki/WinBuilder#Actively_developed_projects

restoring to a different path

 A link dump on restoring a cloned disk to a different path - 

https://drbl.org/faq/fine-print.php?path=./2_System/102_restore_image_to_different_partition.faq#102_restore_image_to_different_partition.faq

https://drbl.org/faq/fine-print.php?path=./2_System/119_larger_to_smaller_disk_restore_clone.faq#119_larger_to_smaller_disk_restore_clone.faq

http://clonezilla.org/clonezilla-live/doc/02_Restore_disk_image/advanced/09-advanced-param.php

recovering after overwriting EFI partition

Tried to install Windows XP on the Macbook running OS X 10.6 and Linux Mint 18.1 dual boot. Though a new primary partition was created at the beginning of the drive, Windows XP refused to install on it, saying there are too many partitions.

In the process, the EFI boot partition was overwritten. So, the machine would not boot. Tried creating a refind boot USB drive - that showed up the Mac and Linux boot loaders, but did not boot either of them - the Linux boot ended in an emergency shell, and the Mac boot ended with the Mac apple turning into a cross, and not booting.

Googled various options, and thought the easiest way would be to do another Linux install. Made another Linux Mint installable USB drive by doing dd of the Mint 18.3 iso to a 16 GB drive, recreated an EFI partition using the installer's GUI partitioning tool, installed the 18.3 to another partition created in free space, and after install, the 18.3 and MacOS were successfully booting.

The original Linux Mint 18.1 was still not booting - dropping into emergency shell. 'Welcome to emergency mode! After logging in, type "journalctl -xb" to view system logs, "systemctl reboot" to reboot, "systemctl default" to try again to boot into default mode.'

journalctl -xb showed that the reason for not booting up was that it was not able to mount /boot/efi with UUID - the UUID had changed, of course, since the boot partition had been re-created. So, just booted into the new 18.3 Linux install, mounted the 18.1 volume, sudo nano edited the /etc/fstab with the UUID from the 18.3's /etc/fstab, and then rebooted - all OK.

Here are some of the things I googled and found - something like rough notes -

enabling bios mode
https://superuser.com/questions/1133040/unable-to-boot-into-windows-10-with-refind-solved/1133052

By reinstalling
http://osxdaily.com/2016/07/28/fix-broken-efi-partition-mac/

in the comments,
https://xpcboot.weebly.com/

Install XP from OS X without bootcamp =
https://discussions.apple.com/thread/5305138

Repair OS X with fsck
https://support.apple.com/en-in/HT203176

Ctrl R for safe boot into OS X
https://kb.wisc.edu/helpdesk/page.php?id=7197

Installing grub alone
https://ubuntuforums.org/showthread.php?t=224351

Dual boot A-Z
https://ubuntuforums.org/showthread.php?t=1649050

leads to installing Windows after Ubuntu -
https://ubuntuforums.org/showthread.php?t=1649050&p=10278677#post10278677

gparted rightclick and set boot flag

https://askubuntu.com/questions/473641/make-boot-partition-using-gparted-in-boot-repair

For my timed out waiting for device
https://bbs.archlinux.org/viewtopic.php?id=213548

which leads to
https://wiki.archlinux.org/index.php/Fstab#Automount_with_systemd

Step by Step instructions on fixing at
https://askubuntu.com/questions/286108/failed-to-mount-boot-efi

Unified Threat Management - UTM devices, proxies etc

In the context of an outage of our Cyberoam device, and the general decrepitness of the college proxies, I took a look at some available options, tuning etc.

https://www.quora.com/Which-is-the-best-Open-Source-Unified-Threat-Management-System-UTM-in-the-market

mentions ClearOS

http://jonmoore.duckdns.org/index.php/network-security/32-open-source-utm

reviews pfsense , untangle and sophos. He has an additional VPN requirement.

Comodo offers a free download.

https://www.google.co.in/search?q=set+up+a+unified+threat+management+appliance+with+open+source+software

For squid tuning, cache size etc,
https://forum.pfsense.org/index.php?topic=24429.0

where a user suggests, for an admin who has trouble with 70 users,

 I recommend use 10KB to 16KB(thumbnail picture size) for object size.
On restart COSS contents will be lost(developent still on progress for this issue)

for your memory issues:
squid/lusca would use 10MB per GB of total cache(when full).
http://wiki.squid-cache.org/SquidFaq/SquidMemory#How_much_memory_do_I_need_in_my_Squid_server.3F

If your system starts to use SWAP file(due to lack of RAM) then it will definitely slows your internet.
Squid/lusca starts to grow Page faults it also affects performance.

You might need to consider changing your cache_mem and give them to your OS.
This FAQ would help you.
http://wiki.squid-cache.org/SquidFaq

temporary router

PB sent me his configuration changes when he put in a temporary router -

1. Editing /etc/network/interfaces to give our mail server a public id (earlier it was in the DMZ)
2. Physically connecting the server with LAN cable to one of the ports of the router.
3. Going to NAT Access Control under Network Options on the router's config page, to disable NAT for the mail server. 

lines seen on camera capture with new SDK

With QHYCCD's new SDK, lines were seen on captures. But on further study, found that the lines were seen when phone LED or LCD screen of computer is used as illumination, not otherwise.

So this is probably due to the effect of the rolling shutter + the repetition rate of the illumination.

We checked with sunlight - no lines - and with SLED illumination - no lines. So we are probably all good.

ways to add files to github

Not only the commandline method,

https://help.github.com/articles/adding-an-existing-project-to-github-using-the-command-line/

https://help.github.com/articles/adding-a-file-to-a-repository-using-the-command-line/

https://help.github.com/articles/changing-a-commit-message/

but also via web interface, which would be easier for me,

https://help.github.com/articles/adding-a-file-to-a-repository/

and creating a new file inside a new folder by directly typing the path like doc/newfile.md etc

https://stackoverflow.com/questions/18773598/creating-folders-inside-github-com-repo-without-using-git

Windows executable slower

Found that an opencv cross-platform executable was running slower on Windows - compiling in Release mode instead of Debug mode did not improve this. Most probably due to the DFT algorithm, which might not be optimized on Windows. There were multiple DFTs called within the image refresh loop. The linux binary ran at 100 fps for 16 bit 320x240 images and 200 fps for 8 bit 320x240, but the windows exe was limited to 64 fps for both 16 bit as well as 8 bit. Linux was running on an i7 Macbook running Mint 18.1, Windows 8.1 was running on an i5 I believe.

Edit - my analysis above seems to be wrong - the code only had the Hilbert transform (and hence the DFT) on press of s key - and the fps was low even when no keys were being pressed. Some other bottleneck. Display driver?  

QHY SDK - Windows and Linux

Found the answer to my query to the QHYCCD helpdesk in November - the difference between the behaviour of Windows software which uses the Windows QHY SDK, and software built using the Linux SDK (and between different versions of the SDK!) are due to different implementations of the SDK.

My query was:

....my question is about frame to frame variations.

For example, I closed the lens cap and took two snapshots. Gain=5, Exposure time = 20 ms. I find that the pixel values are like:

Frame1: 3168   3216   3184   3184 etc

Frame2: 3232   3152   3248   3184  etc

So when i subtract Frame 2 - Frame 1, I get

64  -64  64 0 etc. with a max value of 256.

And this difference increases when there is light falling on the camera.

Is there any way to reduce this frame to frame difference? Any way to reach the 6e performance?

Also, when reducing gain, I find that the image gets saturated at a value below the full 16-bit max value of 65535. For example, with a gain of 5, the saturation happens at an intensity of 27776.

The reply was that the 6e error is the readout noise. The rest of the noise is probably shot noise. 

 The gain values are the numbers entered in Sharpcap (latest version). I have checked with two different QHY5Lii-M cameras. On both, if gain is reduced below 30, saturation occurs below 65535 (in 16bit mode - in 8bit mode, below 255).

For example, as mentioned before, with a gain of 5, whether the exposure is 5 millisec or 5 sec, the max value is only 27776.

But when I code my own capture, using the SDK at
https://github.com/qhyccd-lzr/QHYCCD_Linux

there is a difference - if I change the parameter CONTOL_GAIN

with SetQHYCCDParam(camhandle, CONTROL_GAIN, camgain);

even for value of camgain=1, I am able to see saturation at 255 for 8 bit mode. So, I could use this for my work. Maybe Sharpcap uses a different set of numbers? or a different parameter? as gain. 

The QHY team did not reply, but I found that the Windows and Linux SDKs have a different range for the Gain parameter, and probably for other parameters as well!  The Linux SDK (Software Development Kit) and the Windows SDK are developed by different teams. So, the same functions have different implementations! For example, gain goes from 1-100 in the Linux SDK we tested. But gain goes 1-480 in the latest Windows SDK.

cross platform issues

In order to get the OpenCV code using the QHY camera SDK - originally written on Linux - running on Windows by compiling it with Visual Studio, the following items had to be done.

1. Install the latest Visual Studio Community edition (v. 15, Visual Studio 2017). OpenCV's latest binaries only work with v14 and v15, and if we use some other version of VS, we would have to recompile opencv, which would be a pain.
2. Install the latest QHY SDK from http://www.qhyccd.com/SWHIST_SDK.html - the latest version of the SDK has the lib files, h files and so on in addition to the dll binaries. Currently the latest version is at the bottom of the page!
3. Install the latest version of OpenCV for Windows from sourceforge, following the instructions at https://docs.opencv.org/2.4/doc/tutorials/introduction/windows_install/windows_install.html
4. The instructions on how to build an opencv application, https://docs.opencv.org/2.4/doc/tutorials/introduction/windows_visual_studio_Opencv/windows_visual_studio_Opencv.html#windows-visual-studio-how-to
   is reasonably similar to what we need to do, except for the fact that it would be better if we create a new property sheet called common and save it for future use as mentioned in the next point below - VS15 does not recommend .user property sheets.
5. In a newly created property sheet (called common, for reuse), add the additional include directories, linker files etc as mentioned in the documentation on point 4 above. Here, we need to add the QHY SDK includes and dlls also. The opencv libraries are now distributed as a single file, opencv_world.lib and not the multiple lib files as in the documentation above. So, in short,
   
   VC++ directories -> Include
   Linker General -> Additional Library directories
   Linker Input -> names of the lib files in Additional Dependencies 
6. The .cpp files need to have ifdefs for linux and windows standard headers separately. Code can be seen at https://github.com/hn-88/ASKlive/blob/master/ASKlive.cpp
7. For the C function sprintf to work, the following pre-processor directive has to be added - C++ -> Preprocessor - > Preprocessor definitions -> add _CRT_SECURE_NO_WARNINGS
8. In order to copy over the required DLLs, the following post build event has to be added -
   xcopy /y /d "D:\qhy\*.dll" "$(OutDir)"
   xcopy /y /d "$(OPENCV_DIR)\bin\*.dll" "$(OutDir)"
   It is safer to copy to the executable's directory, since there is quite a bit of confusion about copying to system folders - http://www.forceflow.be/2012/04/04/the-3264-bit-dll-confusion-on-windows-64-bit/
9. Arrays have to be pre-assigned sizes - can't be assigned sizes at runtime as with GNU C compiler. 

Edit 3 June 2018 - 10. Added this line of code to prevent the "exe has stopped working" Windows dialog box on exit - 

SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOGPFAULTERRORBOX);

via stackoverflow, with additional documentation at msdn. 

Raspberry PI configuration link dump

1. Installation - https://www.raspberrypi.org/documentation/installation/noobs.md
   http://qdosmsq.dunbar-it.co.uk/blog/2013/06/noobs-for-raspberry-pi/
   
   
2. Impressive - The Raspberry Pi 3 boots up in 25 seconds to Desktop. 10 seconds to open Chromium browser. 25 seconds to load a google spreadsheet. Overall, faster than my AMD64 Windows XP laptop from 2009. :)
   
   
3. Older version of RPi (Pi2?) - good for playing local videos - was pleasantly surprised to find that I could just put in the same micro-SD card which was running Raspbian 9 into a SD-card adapter and put it into the older Pi, and it booted and ran fine - did not need any reinstall.
   
   
   It is good for playing local videos. It could play 2 windows with 2 instances of VLC running local copies of 360p videos without any problems - 35% CPU for each instance, MP4 and DIVX respectively. But it could not play videos reliably over the network. Also, web browser Chromium takes a very very long time to open, web pages crawl to load. Probably because of the low RAM.
   
   
   But I can use it as a video player, with a status message at the bottom or something like that.
   
   
4. Ubuntu 64 bit on the new Pi - https://www.raspberrypi.org/forums/viewtopic.php?t=220079
   

   sudo cp ~/Desktop/pi-bootloader/boot/* /mnt

   
   

   
   

   Instead, doing this - 

   https://ubuntu-mate.org/raspberry-pi/

   
   

   with the image at

   http://cdimage.ubuntu.com/releases/18.04/release/ubuntu-18.04.2-preinstalled-server-arm64+raspi3.img.xz
   
   
5. Only xubuntu available for Pi - https://linuxconfig.org/install-ubuntu-16-04-mate-or-ubuntu-18-04-on-raspberry-pi#h7-1-ubuntu-server-unofficial
   
   
6. wifi driver installation - https://www.youtube.com/watch?v=nlLS8d4Z09c
   lspci -vvnn | grep 802
   
   
   lsusb does not show it when driver is not installed.
   https://askubuntu.com/questions/246236/compile-and-install-rtl8192cu-driver
   
   
   https://askubuntu.com/questions/629522/rtl8188ce-step-by-step-guide
   
   https://elinux.org/RPi_USB_Wi-Fi_Adapters
   
   
7. Cloning RPi with dd - https://www.raspberrypi.org/forums/viewtopic.php?t=46911
   sudo fdisk -l
   sudo dd bs=4M if=/dev/sdc | gzip > /home/your_username/image`date +%d%m%y`.gz
   sudo gzip -dc /home/your_username/image.gz | dd bs=4M of=/dev/sdc
   
   
8. Enabling monitoring on RPi wifi - https://raspberrypi.stackexchange.com/questions/36747/enable-monitoring-mode-for-rtl8188cus-via-usb-on-raspbian
   
   
9. How to loop in VLC - https://forum.videolan.org/viewtopic.php?t=78723 - and subtitles in vlc playlist maker.
   
   
10. Adjusting Overscan on the RPi - https://retropie.org.uk/forum/topic/2371/using-composite-video-can-t-see-everything-on-the-screen/16
    
    
11. Raspberry PI model comparison - http://socialcompare.com/en/comparison/raspberrypi-models-comparison
    
    
12. Shortcut to edit text file -  Exec=leafpad %U /home/pi/file.txt

securing lighttpd

Brief notes on securing lighttpd, the light-weight web-server - 

https://www.packtpub.com/mapt/book/networking_and_servers/9781847192103/7

# deny access to all files below a certain path
$HTTP["url"] =~ "/certain-path/" { url.access-deny = ("") }
# deny access on all jpeg images to the Google bot
$HTTP["useragent"] =~ "Google" { url.access-deny = (".jpg") }
# deny access by referrer
$HTTP["referrer"] !~ "^($|www.ourhost.com)" {
url.access-deny = ("")
}

under mod_access

and also passwd auth.

QHY camera glitch

After removing the new SDK files from Linux Macbook in order to test the camera again with the old SDK, the QHY5L-ii camera was not being recognized on the Linux machine at all. Both cameras, on both USB ports, LED does not light up, no dmesg messages either.

Tried on another Linux machine - Acer running Ubuntu 16 - without any drivers installed - again, no dmesg messages.

Tried changing the USB cable - then a dmesg message was seen, detecting on a 'slow port'. Tried on the Macbook again after reinstalling the new SDK, now it was showing dmesg messages as well as LED lighting up - detected OK. Changed back to the original USB cable - everything still OK.

So, probably a combination of hardware and firmware issues.