Karl Marx CooleyTukey

Motivatation

modern CMake is required for building a lot of new software
CMake is dependency for many packages (e.g. ROS related)
we don't want to remove CMake (which would remove packages that depend on it)
we want safe procedure to update CMake that can be reversed easily

Current version in OS

Check current version

sysrq magic keys

This is useful for trying to recover from an unresponsive system. However, by default, Ubuntu disables the key to gain raw keyboard access.\

Sometimes part of the issue is that X/Wayland display servers have crashed due to bad graphics drivers and keyboard input isn't processed anymore, whereby changing to another console, e.g. ctrl + alt + F1 doesn't work. Since the default disables keyboard control, alt + sysrq + r, can't help salvage the situation. Hence the suggestion to at least enable system request raw keyboard control when trying to recover a system.

Ubuntu doesn't enable control of keyboard by default

Ubuntu 16.04 LTS default value:

set http or socks proxy environment variables

# set http proxy
export http_proxy=http://PROXYHOST:PROXYPORT

# set http proxy with user and password
export http_proxy=http://USERNAME:PASSWORD@PROXYHOST:PROXYPORT

# set http proxy with user and password (with special characters)

To remove a submodule you need to:

Delete the relevant section from the .gitmodules file.
Stage the .gitmodules changes git add .gitmodules
Delete the relevant section from .git/config.
Run git rm --cached path_to_submodule (no trailing slash).
Run rm -rf .git/modules/path_to_submodule (no trailing slash).
Commit git commit -m "Removed submodule "
Delete the now untracked submodule files rm -rf path_to_submodule

To limit a CPU to a certain C-state, you can pass the processor.max_cstate=X option in the kernel line of /boot/grub/grub.conf.

Here we limit the system to only C-State 1:

    kernel /vmlinuz-2.6.18-371.1.2.el5 ... processor.max_cstate=1

On some systems, the kernel can override the BIOS setting, and the parameter intel_idle.max_cstate=0 may be required to ensure sleep states are not entered:

	#include <iostream>


	// get_type<i, Ts...>::type -> Ts[i] (Compile error of i >= length(Ts))
	template<size_t i, typename T, typename... Ts>
	struct get_type {
	typedef typename get_type<i - 1, Ts...>::type type;
	};

	template<typename T, typename... Ts>

	### KERNEL TUNING ###

	# Increase size of file handles and inode cache
	fs.file-max = 2097152

	# Do less swapping
	vm.swappiness = 10
	vm.dirty_ratio = 60
	vm.dirty_background_ratio = 2

	SAN_CMP := -fno-omit-frame-pointer -fsanitize=address
	SAN_STAT := -static-libstdc++ -static-libasan

	BIN_CMP := -std=c++11 -c -I. main.cpp -O -g3 -o main.o
	LIB_CMP := -std=c++11 my.cpp -o libmy.so -shared -fPIC -g3

	RUN := LD_LIBRARY_PATH=. ASAN_OPTIONS=symbolize=1 ASAN_SYMBOLIZER_PATH=$(shell which llvm-symbolizer)
	PRELOAD := LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libasan.so.1

	lib-gcc:

	from threading import Thread
	import Queue
	import time

	class TaskQueue(Queue.Queue):

	def __init__(self, num_workers=1):
	Queue.Queue.__init__(self)
	self.num_workers = num_workers
	self.start_workers()

	1. Execute make first. This will result in a netlinkKernel.ko output among many others.
	2. Execute $ gcc netlinkUser.c -o netlinkUser
	3. Insert kernel module by :$ sudo insmod netlinkKernel.ko
	4. Run ./netlinkUser to see message and run dmesg to see debug messages
	5. Remove module by : $ sudo rmmod netlinkKernel
	6. Finally make clean to remove output files.