Increase USBFS memory limit in Ubuntu

When using USB3 camera on Linux you may face this USB memory limit issue.
By default, Linux limits image capture to 2 MB. To capture images over 2 MB, extend the USBFS limit on how many buffers can be locked into the driver.

sudo sh -c 'echo 1000 > /sys/module/usbcore/parameters/usbfs_memory_mb'

To confirm that you have successfully updated the memory limit, run the following command:

cat /sys/module/usbcore/parameters/usbfs_memory_mb

To set the maximum usbfs memory limit permanently:
Open the /etc/default/grub file in any text editor. Find and replace:


with this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash usbcore.usbfs_memory_mb=1000"

Update grub with these settings:

$ sudo update-grub

You need to reboot the system after updating grub.

Fail2ban – Prevent Postfix Brute Force


# apt-get install fail2ban

To limit memory usage, add to /etc/default/fail2ban:

+ulimit -s 256

Local config file
Create a local config file /etc/fail2ban/jail.local to override settings in jail.conf:

To ban authentication via SSH after 3 failed attempts add the following to /etc/fail2ban/jail.local:

enabled   = true
port      = ssh
filter    = sshd
logpath   = /var/log/auth.log
maxretry  = 3


# /etc/init.d/fail2ban restart

Postfix and Dovecot
To ban authentication to Postfix and Dovecot after 3 failed attempts add the following to /etc/fail2ban/jail.local:

enabled = true
port = pop3,pop3s,imap,imaps
filter = dovecot
logpath = /var/log/mail.log
maxretry  = 3

enabled  = true
port     = smtp,ssmtp
filter   = postfix
logpath  = /var/log/mail.log
maxretry  = 3

enabled   = true
port      = smtp,ssmtp,imap2,imap3,imaps,pop3,pop3s
filter    = sasl
logpath   = /var/log/mail.log
maxretry  = 3

Fail2ban (Debian Squeeze) isn’t shipped with a configuration for Dovecot, so create /etc/fail2ban/filter.d/dovecot.conf:

failregex = (?: pop3-login|imap-login): .*(?:Authentication failure|Aborted login \(auth failed|Aborted login \(tried to use disabled|Disconnected \(auth failed).*rip=(?P\S*),.*
ignoreregex =

Restart fail2ban:

# /etc/init.d/fail2ban restart

To ban IPs after 3 failed login attempts add the following to /etc/fail2ban/jail.local:

enabled = true
port    = http,https
filter  = apache-auth
logpath = /var/log/apache*/*error.log
maxretry = 3

Copy Large amount of data using rsync

Copying large amount of data,like 300 or 400GB’s from one hdd to another using nautilus or any file manager may fail on some occasions. Using the command rsync will be a better idea to copy large piles of data. This will show the progress percentage and the amount of data copied.

rsync -ah --info=progress2 SOURCE_PATH DESTINATION_PATH

change SOURCE and DESTINATION path according to your needs.

Install and Configure OpenCV in Code Blocks

First install dependency packages

Install Code Blocks IDE

sudo apt-get install codeblocks

Required packages

sudo apt-get install build-essential
sudo apt-get install cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev

Optional packages

sudo apt-get install python-dev python-numpy libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libjasper-dev libdc1394-22-dev

Clone the latest OpenCV from github

git clone

Compile and Install

cd ~/opencv
mkdir release
cd release

For using with QT and OpenGL and for sample code snippets use this cmake


Screenshot from 2016-08-02 23:45:46

Screenshot from 2016-08-03 00:17:29

sudo make install

Screenshot from 2016-08-03 00:17:58

Now open CodeBlocks.Now go to settings –>compiler
Under the compiler settings tab select the other options tab and copy the following command into the pane.

`pkg-config opencv --cflags`

Screenshot from 2016-08-09 21:01:57

Now open the Linker Settings Tab and copy the following command int the other linker options pane:

`pkg-config opencv --libs`

Screenshot from 2016-08-09 21:02:48

Click OK to save the settings.

Happy Hacking 🙂

Syncing Heroku and GitHub repos

First add them:

git remote add origin 
git remote add herkou

In case if you want to clone and add

git clone
git remote add origin

Push and Pull in Github

git remote -v
git pull origin master -- pull from Github Master branch
git push origin master -- push to Github Master branch

Pushing to Heroku

git remote add origin 
git remote add herkou
git push heroku master -- push to Heroku

Authentication token manipulation error

One of my friend forgot his ubuntu password and i tried to fix it by going to recovery mode dropping into root shell and resetting the password for the user

root@username-PC:~# passwd username
Enter new UNIX password:
Retype new UNIX password:
passwd: Authentication token manipulation error
passwd: password unchanged

But this time it didn’t work as usual. It showed an error “Authentication token manipulation error”.
I tried googling an found that the file system is not mounted with read/write permission.
From root shell remount file system with read/write permission.

mount -rw -o remount /

Then try changing the password using

passwd username

Some times it may may throw the same error again, then delete the password for the user from /etc/shadow file using the fllowing command

sudo passwd -d username

Replace username with your’s. Then again change the password using

passwd username

Happy Hacking 🙂

How to fix a “Problem with MergeList” or “status file could not be parsed” error

I recently got this error, usually may happen after a Heroku toolbelt setup

E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages
E: The package lists or status file could not be parsed or opened.

you wont be able to update through terminal too

Screenshot from 2016-04-30 14:56:09

Open Terminal and issue this command

sudo rm -vf /var/lib/apt/lists/*

Generate a new list by doing a update

sudo apt-get update

Happy Hacking 🙂