Shell command to shutdown or reboot Ubuntu

Open shell or terminal in Ubuntu;

Alt+F2 > Terminal

To shutdown or poweroff Ubuntu

Type the command:

$ sudo shutdown -h now
or
$ sudo halt

-----------------

To reboot Ubuntu

Type the command:

$ sudo reboot

-----------------

Linux Directory Structure

Directory    Description

/bin/         User commands and binaries.
/boot/       Files used by the boot loader.
/dev/         Device files.
/etc/          System configuration files.
/home/      User’s home directories.
/lib/           Shared libraries and kernel modules.
/media/     Removable media is usually mounted here.
/mnt/        Temporary mounted file systems are usually mounted here.
/opt/         Add-on application software packages.
/proc/       Kernel and process status data is stored in here in text-­ file format.
/root/       The root user’s home directory.
/sbin/        System binaries.
/srv/         Data for services provided by this host.
/tmp/        Directory for temporary files.
/usr/         User utilities, libraries, and applications.
/var/         Variable or transient files and data, for example logs, mail queues, and print jobs.

Protect Ubuntu from Fork Bombs

In computing, the fork bomb is a form of denial-of-service attack against a computer system which makes use of the fork operation (or equivalent functionality) whereby a running process can create another running process.
A fork bomb works by creating a large number of processes very quickly in order to saturate the available space in the list of processes kept by the computer's operating system. If the process table becomes saturated, no new programs may start until another process terminates.

the following example may look innocent, but running it on an unprotected system may take the whole system down:

Do not run this code on an unprotected system!

$ :(){ :|:& }; :

The above shell script will actually keep forking at an exponential rate until system resources are exhausted.
To protect a system against such attacks, there is a file for limiting the number of processes per user. It is /etc/security/limits.conf. Add the following two lines to it:

*            hard       nproc                    20

user       hard       nproc                   300

or

@users          soft       nproc                  100
@users          hard       nproc                  150

These lines prevent anyone in the users group from having more than 150 processes, and issue a warning at 100 processes.
Your system may not have a users group, so you may want to edit the lines to match your needs.

LuckyBackup

LuckyBackup

... a powerful, fast and reliable backup & sync tool.
schedule, manage backup/sync, restore procedures, and much more...



luckyBackup is an application for data back-up and synchronization powered by the rsync tool.

It is simple to use, fast (transfers over only changes made and not all data), safe (keeps your data safe by checking all declared directories before proceeding in any data manipulation ), reliable and fully customizable.

http://luckybackup.sourceforge.net/index.html

Install;

Alt+F2 > Terminal

$ sudo apt-get install luckybackup

Boot-Repair

Boot-Repair is a small graphical tool to restore access to Ubuntu and other OS (Windows..).
One "Recommended repair" button to repair most frequent boot problems. (generally repair filesystems and reinstall Grub2)

Another button to create a Boot-Info-Script summary in 1 click

Options to reinstall Grub2 easily (OS by default, purge, unhide, kernel options..), and other advanced options (MBR restore...).

Boot-Repair is a free software, licensed under GNU-GPL. Boot-Repair is not officially supported by Canonical, use it at your own risks.



ALT+F2 > Terminal or Terminator

$ sudo add-apt-repository ppa:yannubuntu/boot-repair
$ sudo apt-get update
$ sudo apt-get install -y boot-repair && boot-repair

ALT+F2 > boot-repair