Ubuntu.txt

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-1) For BINP local network it is mandatory to disalbe avahi daemon:
	sudo systemctl disable avahi-daemon
	sudo systemctl stop avahi-daemon
    Check with:
    	service --status-all
UPD: Firefox seems to restart it constantly anyway. Had to
	sudo apt-get remove avahi-daemon
UPD: Or use
	systemctl mask avahi-daemon.socket

 0) It's better to use Dolphin File Manager (default in SL7):
	via Software Center (easier than using bash)

 1) Ubuntu 15.10 GUI copy bug: coping form shared directory (owned by root, I gather this is the issue for any not user ownned
directory, but haven't checked) to some directory will fail if files with such names had been already copied to the target
location, even if they were later removed! Instead of coping of new files old ones are either stay or restored. This was on
Oracle Virtual Box machine. Use terminal's >cp $from_file $to_file instead.

 2) Virtual Box can change the number of processors without worry in between guest OS launch.

 3) mouting shared folder:
Install virtual drive drivers: VBox's menu (left Ctrl+Home by default): Devices->Insert Guest Additions CD Image
then auto installation will run

	>sudo -i //enter root
	>password entering
	>mount -t vboxsf $HostFolderNameInVirtualBox $where to mount (must exist - not created)
change of owner (does not seem to work):
	>chown $USER -R $path_to_folder //$USER is a real env. var.
	>exit //from root

 5)

 6)Commands
echo - display:
	>echo $GARFIELD_HOME
prints the value of GARFIELD_HOME environment variable
	>export GARFIELD_HOME=/home/perser/Documents/GarfieldPP
	>export HEED_DATABASE=$GARFIELD_HOME/Heed/heed++/database
creates env. variables
	>source $file_name.sh
runs .sh file. Works when simple file_name.sh is denied access.
use this command to initialize root env. vars. (thisroot.sh)
https://superuser.com/questions/46139/what-does-source-do
	>cp $from_file $to_file
copy
	>ls
list directories
	>rmdir
removes dir
	>apt-get target install $package_name
loads and installs package
	>./CellTest
executes CellTest program (in the same directory)
	>command && (command1 ; command2) || (command3)
executes command. If it exists with error code (returns not 0) command3 executed otherwise command1 and 2 are consecuvely
executed. If any fails 3 executed.
example:>make && (echo -e "make ok\n"; .Cell)|| (echo -e "make error\n")
-e flag enables special characters
; allows several commands in one line

 7) In order to change vhd disk location in the host OS modification of Oracle VM file required, it is impossible to do
via GUI (disconnecting disk, relocating it and connecting again yields 'the disk with number ... is already registered' error)
Go to C:\Users\$(USER_NAME)\VirtualBox VMs\$(VM_NAME) and change disk path in the .vbox file.

 8) Installing SWAP disk (optionnaly may delete previous swap):
	1) Add disk to virtual machine
	2) Format it (was done via Disks GUI programm)
	3) (NOT optionally for the swap disk:) set mount options (mount at startup, select label and mount point(folder))
	4) In mounted point (/media/perser/swapDisk in my case) create a file with desired swap size):
>fallocate -l 21g /media/perser/swapDisk/swap
(if file size exceeds available space file will be created with all available space used)
	5) >sudo chmod 600 /media/perser/swapDisk/swap
For security
	6) >sudo mkswap /media/perser/swapDisk/swap
	7) >sudo swapon /media/perser/swapDisk/swap
Now swap is set up but after reboot 'sudo swapon /media/perser/swapDisk/swap' will have to be repeated.
	8) In order to set up swap at setup add line to /etc/fstab (i.g. via >sudo gedit /etc/fstab):
	/media/perser/swapDisk/swap none swap sw 0 0
Beware that this line must go after /media/perser/swapDisk has been mounted (that's why 3rd point was required, note that
disk mount is listed in the /etc/fstab), because file can't be used as swap if system has not connected the disk
containing it yet. In case of automount of swap disk this line has no effect.

 9) Setting environment variables and launching scripts at statup.
	1) move .sh script to /etc/profile.d
Note that LD_LYBRARY_PATH is an exception and can only be set interactively in terminal or using /etc/ld.so.conf.d/*.conf
configuration files. (Required for Elmer for example)
	2) Add files to /etc/ld.so.conf.d/*.conf with path to libraries, e.g.:
	>sudo touch /etc/ld.so.conf.d/elmer.conf
	add "/mnt/formerSwap/Elmer/install/lib" to that file
	and >sudo ldconfig
		(only once, not required at the system boot)

	3) //UPD: does not work.// Also mounting is impossible in /etc/profile.d, so mounting shared with Host folder must be
done via 
	adding <name_of_share>   /path/to/mountpoint   vboxsf   <options>  0   0
	to the /etc/fstab file:
		1) For mount of shared with host folder to be available user (perser in my case) must be int vboxsf group:
		>sudo usermod -a -G groupName userName
		>sudo usermod -a -G vboxsf perser	
		2) Next instead of
		>sudo mount -t vboxsf SharedVirt /home/perser/Shared
		use 
		SharedVirt   /home/perser/Shared   vboxsf   auto  0   0
		in the /etc/fstab
	3) >sudo mount -t vboxsf SharedVirt /home/perser/Shared
Only this seems to work 

10) For Eclipse remote debugging:
	Make /proc/sys/kernel/yama/ptrace_scope permanent to 0 by setting ptrace_scope to 0 in /etc/sysctl.d/10-ptrace.conf

11) For Eclipse profiling (perf): //UPD: does not work at all
	Install perf (google, via apt-get)
Determine current value: >cat /proc/sys/kernel/perf_event_paranoid
	How to change /proc/sys/kernel/perf_event_paranoid (to 0 or 1) (otherwise permission denied error):	   
	add line
		kernel.perf_event_paranoid=1
	to /etc/sysctl.conf (Persistant change)
	OR
	sudo -i
	echo 1 >/proc/sys/kernel/perf_event_paranoid
	exit (Per session change)

12) Archives:
	create simple zip from "input" folder:
	> zip -9 -r output.zip input
	-r means recursion (zip subfolders). -9 is a mamimal compression level (slowest). default is -6 (from 0 to 9).
	By default zip uses deflation algorithm. bzip2 may be better:
	> zip -Z bzip2 -r output.bz2 input
	But archive manager cannot view content of bz2 files.
	Delete folder/files from existing archive (WILL unzip/create temporary .zip):
	>zip -d foo foo/tom/junk foo/harry/\* \*.o
	will  remove  the  entry  foo/tom/junk,  all  of  the  files  that  start  with
	foo/harry/,  and  all  of  the files that end with .o (in any path).
	It is not recursive, so if archive has files in 191128/f1/data1.dat, data2.dat ...
	use >zip -d archive archive/190228/f1/\* to detele these files
	To add password pretection use -e flag:
	>zip -e -9 -r output.zip input

13) Remote disk (at lab)
	Conntcted via File Manager
	smb://192.168.162.104/NAS2_Vol1/
	To operate with it via bash mountpoint is required.
	To get how File Manager set it: open it -> open in teminal.
	In my case it's /run/user/1000/gvfs/smb-share:server=192.168.162.104,share=NAS2_Vol1/
	Works as usual path.

14) Lost files restoration
	TestDisk:
	> sudo apt-get install testdisk
	To run it on the main device run
	> sudo testdisk /dev/nvme0n1p2
	To get disk mount locations use	
	> sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL
	to list devices and
	> mount
	to get mountpoints

	testdisk is quite smart and will highlight correct choices to select by default
	Up until Partition menu with [Type] [Superblock] [List] ... on the bottom
	Select [List] there and navigate to lost file/folfer
	Select them and copy to location where they should be restored
	Note that they will be put in folder with whole path!
	> sudo chown -R $USER Folder
	To change user for whole folder (after resoration the file will be be owned by root) 

15) Profiling on Ubuntu using QtCreator:
	Open QtCreator
	Create new project - plain c++ console application
	Build system - qmake
	After that - .pro file contains projects setups

	//For compiler flags use:
	QMAKE_CXXFLAGS += -fPIC
	QMAKE_CXXFLAGS += -pthread

	QMAKE_LFLAGS += -fPIC
	QMAKE_LFLAGS += -pthread
	QMAKE_LFLAGS += -pipe

	//For sources use:
	SOURCES += \
        src/ArgonParticle.cpp \
        src/ArgonVanDerWaals.cpp \
		... \
		src/main.cpp
	//Note that there is no '\' for the last file

	//It you want to pass file as parameter to Qt-built console application, it is necessary to add this file: 
	DISTFILES += \
    	settings.xml

	HEADERS += \
		include/ArgonParticle.h \
		include/ArgonVanDerWaalsParticle.h \
		... \
		include/ColoredInterval.h

	unix:!macx: LIBS += -L$(HOME)/Software/root_v6.14.06/build/lib/ \
		-lpthread \
		-lGui \
		-lCore \
		-lRIO \
		-lNet \
		-lHist \
		-lGraf \
		-lGraf3d \
		-lGpad \
		-lTree \
		-lRint \
		-lPostscript \
		-lMatrix \
		-lPhysics \
		-lMathCore \
		-lThread \
		-lMultiProc \
		-lGeom \
		-lm \
		-lSpectrum \
		-lThread

	INCLUDEPATH += $(HOME)/Software/root_v6.14.06/build/lib
	INCLUDEPATH += $(HOME)/Software/root_v6.14.06/build/include
	INCLUDEPATH += $(HOME)/Software/boost_1_67_0
	INCLUDEPATH += $(HOME)/Documents/QtThreeDimSimulation/QtThreeDimSimulation/include
	DEPENDPATH += $(HOME)/Software/root_v6.14.06/build/lib
	DEPENDPATH += $(HOME)/Software/root_v6.14.06/build/include
	DEPENDPATH += $(HOME)/Software/boost_1_67_0
	
	After project setup:
	Build app to check that everything is all right
	Setting up build configurations (Working directory/{Release, Debug, Profile}, etc):
	Left menu->Projects
	
	Profiling: Top Menu->Analyze->Performance Analyzer

16) convert all .*png to .pdf:
	cd $folder_with_files
	for f in $(find . -name '*.png'); do convert "$f" "${f%.*png}.pdf"; done

17) Checking SSD health:
    sudo smartctl -a /dev/nvme0
  Do not use /dev/nvme0n1p1 - namespace or partition, otherwise there will be NVMe Status 0x4002 error.

18) Finding and replacing every occurrence of oldtext with newtext in every text file under the /some/folder/ directory tree recursively:
	grep -rl --include=\*.h oldtext . | xargs sed -i 's/oldtext/newtext/g'
	
19) Setting up gnome / dock interface:

# Docks (left panels) are separate for each wokspace
gsettings set org.gnome.shell.extensions.dash-to-dock isolate-workspaces true
# Remove trash icon from the Dock
gsettings set org.gnome.shell.extensions.dash-to-dock show-trash false
# Remove mounted discs from the Dock
gsettings set org.gnome.shell.extensions.dash-to-dock show-mounts false

20) Making global aliases: add
    alias python='python3'
to /etc/bash.bashrc script (profile.d may be ignored)

21) Saving and loading terminal settings:
	dconf dump /org/gnome/terminal/ > gnome_terminal_settings.txt
	dconf load /org/gnome/terminal/ < gnome_terminal_settings.txt
	
22) Extend virtual drive from guest ubuntu
    https://unix.stackexchange.com/questions/196512/how-to-extend-filesystem-partition-on-ubuntu-vm :
    sudo growpart /dev/sda 1
    sudo resize2fs /dev/sda1
    
23) Fix _apt missing write permissions (Download is performed unsandboxed as root as file '...' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied):
	https://askubuntu.com/questions/908800/what-does-this-apt-error-message-download-is-performed-unsandboxed-as-root :
	sudo chown -Rv _apt:root /var/cache/apt/archives/partial/
	sudo chmod -Rv 700 /var/cache/apt/archives/partial/
	
24) Alt+Shift language changing:
	# gsettings set org.gnome.desktop.wm.keybindings switch-input-source "['<Alt>Shift_L']"
	# gsettings set org.gnome.desktop.wm.keybindings switch-input-source-backward "['<Alt>Shift_L', '<Shift>XF86Keyboard']"
	# gsettings set org.gnome.desktop.wm.keybindings switch-input-source "['<Alt>Shift_L', 'XF86Keyboard']"
	UPD: Do not use above, it has language popup that forcefully exits fullscreen. Instead use:
	1. Disable default combintation for layout switching in Settings => Keyboard Shortcuts => Typing
	2. Install gnome-tweaks and turn on your new key layouts: gnome-tweaks => Additional Layout Options => Switching to another layout

25) For Hyper-V guest, to make ubuntu see virtual disk at its maximum capacity
    sudo apt-get install cloud-guest-utils -y
    sudo growpart /dev/sda 1
    sudo resize2fs /dev/sda1