Mike's tips

Various stuff I forget, sometimes.

Turning off ASLR on Linux

We can see the ASLR status in the file

/proc/sys/kernel/randomize_va_space

The following values are supported:

0 – No randomization. Everything is static.
1 – Conservative randomization. Shared libraries, stack, mmap(), VDSO and heap are randomized.
2 – Full randomization. In addition to elements listed in the previous point,
    memory managed through brk() is also randomized.

So, to disable it:

echo 0 | sudo tee /proc/sys/kernel/randomize_va_space

and to enable it again, run

echo 2 | sudo tee /proc/sys/kernel/randomize_va_space

This won't survive a reboot, so you'll have to configure this in sysctl. Add a file /etc/sysctl.d/01-disable-aslr.conf containing:

kernel.randomize_va_space = 0

should permanently disable this.

Various tips for diffing two files

Diffing files in two columns

diff -y -W 160 dqn.py others/VashishtMadhavan/dqn.py |less

where -y means line by line. and -W 160 means width (in chars of the output).

Good visual-style vim-related diff

vimdiff dqn.py others/dqn.py

How to print all variables in a tensorflow graph

tf.get_collection(tf.GraphKeys.GLOBAL_VARIABLES)

How to run tensorflow computation only on one GPU

It is done by setting an environment variable CUDA_VISIBLE_DEVICES to a comma separated list of wanted GPUs.

import os
os.environ['CUDA_VISIBLE_DEVICES'] = "1"

How to run exploit so you can still type things into shell

if we finish the first process before the pipe, we won't be able to pass input to the second!

(python exploit.py; cat) | /opt/protostar/bin/stack5

How to screenshot part of screen in Ubuntu 16

gnome-screenshot -a

How to quickly kill a process using port 8000 in Linux?

fuser -k 8000/udp

fuser comes from apt-get install psmisc

How to show all network connections in unix?

netstat -natpe

You can also grep it netstat -natpe | grep 7001

netstat comes from sudo apt-get install net-tools

How to stop displaymanager

systemctl isolate multi-user.target
# disable the graphical target

sudo service lightdm stop
# manual stop of window manager often still needed ¯\_(ツ)_/¯

sudo service gdm3 stop

modprobe -r nvidia-drm
#  Unload the drivers

rmmod
# also unloads the drivers

systemctl start graphical.target
# restarts the graphical target

Various other tricks for installing NVIDIA CUDA etc

dpkg -l | grep nvidia search

sudo apt-get purge nvidia*
sudo apt-get autoremove
sudo sh cuda-*.run --silient --override

Driver:   Installed
Toolkit:  Installed in /usr/local/cuda-10.2/
Samples:  Installed in /home/mike/, but missing recommended libraries

Please make sure that
 -   PATH includes /usr/local/cuda-10.2/bin
 -   LD_LIBRARY_PATH includes /usr/local/cuda-10.2/lib64, or, add /usr/local/cuda-10.2/lib64 to /etc/ld.so.conf and run ldconfig as root

To uninstall the CUDA Toolkit, run cuda-uninstaller in /usr/local/cuda-10.2/bin
To uninstall the NVIDIA Driver, run nvidia-uninstall

How to setup the standard python env

pipenv --python=python3.7

Check what ubuntu / debian you have

lsb_release -a

check what stuff you have connected HW-wise

lscpu. The lscpu command reports information about the cpu and processing units. ...
lshw - List Hardware. ...
hwinfo - Hardware Information. ...
lspci - List PCI. ...
lsscsi - List scsi devices. ...
lsusb - List usb buses and device details. ...
Inxi. ...
lsblk - List block devices

list installed packages in apt

sudo apt list --installed

show where debian package is installed

dpkg -L linux-tools-4.15.0-197

check linux kernel version

uname -r

super hardcore system reboot in linux

systemctl --force --force reboot

What are the various keybindings that work both in Emacs and by default in Mac OS?

Shortcut	Wat it does
C-a	go to beginning of the line
C-e	go to end of the line
C-l	redisplay
C-k	Erase from cursor to end of line
C-d	Erase next character
C-h	Erase last character
C-w	Erase previous word
C-p	Show previous command
C-n	Show next command
C-b	Move back one char
C-f	Move forward one char
M-b	Move back one word
M-f	Move forward one word
C-j	Execute command
C-t	Transpose last two chars
M-t	transpose two last words
`<Del>`	Delete the character just before the cursor
C-h	#SHELL ONLY# Delete the character just before the cursor
C-d	Delete the next character after the cursor
M-`<Del>`	Kill the word immediately before the cursor
C-w	#SHELL ONLY# Kill the word immediately before the cursor
C-d	delete next character
M-d	Kill the next word after the cursor
C-k	Kill from the cursor position to end of line
M-k	Kill to the end of the current sentence

emacs	Wat does it does xD
C-x C-f	Find a file
C-g	Cancel whatever you trying to do
C-x C-s	Save a file
C-x C-b	List buffers
C-x C-f	Find file
C-x C-s	Save file
C-x s	Save some buffers
C-x C-b	List buffers
C-x b	Switch buffer
C-x C-c	Quit Emacs
C-x 1	Delete all but one window
C-x u	Undo
C-x 1	kill all screens but this one
C-x 2	make 2 windows
C-x 3	make 2 windows vert
C-x 0	switch to the other window
C-s	search

Rarer vim trix

Vim
C-e	move screen up one line
C-y	move screen up one line
C-u	move screen up half page
C-d	move screen up half page
C-b	move screen up one page
C-f	move screen up one page
`:%!xxd`	to switch into hex mode
`:%!xxd` -r	switch back from hex mode
ZZ	same as :qw but in normal

Compression, tar, etc

general	Wat it does
tar cvf arch.tar file1 file2 ....	creates an arch
tar xvf arch.tar	extract an arch
tar tvf arch.tar	table contents of an arch
find /dir/to/search -name whatfile.txt -print	self-explainatory
grep search-dis-pattern where (-A -B -C 10)	grep for a pattern
du -sh * \| gsort -h	display disk usage sorted
zip -r archive.zip *	packup dir to zip

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