I created an Ubuntu server. Do I have a «root» user?

The main two commandline possibilities are:

• Use su and enter the root password when prompted.
• Put sudo in front of the command, and enter your password when prompted.

You shouldn’t need to use root to get rid of a segmentation fault. If root is the only thing that fixes a segfault, then the program has a bug. Programs should not fail like that just because they don’t have root.

If you install the package only for yourself (your own home-dir), you don’t need to become root at all. Neither should you have to become root to «install» it so you can then create a binary-package of it. You only need to become root to actually install the package you created system-wide with the package-manager.

How can I install an RPM on a machine where I don’t have root permissions? I want to install a package for my use only in a personal work directory. I’m running SuSe SLES10.

Please don’t flame me with «This idea is so dumb, you shouldn’t do it because all requests must go through the corporate root god, may he live forever.»

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asked Nov 11, 2010 at 18:08

answered Nov 12, 2010 at 9:52

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OK, so I know you shouldn’t install as root

/etc/apache2/envvars

export APACHE_RUN_USER=www-data
export APACHE_RUN_GROUP=www-data

Debian for instance asks at the installation if you want to use root; if not sudo based system is installed.

1 important thing: make sure you use a strong password when using root and don’t give it out to others.

Who is this running as, root or www-data?

• the original service is run as root
• apache then spawns childs processes that are run as the apache user (in this case www-data)

Sudo runs the installer program as root. This does not mean that the program will run as root. All normal program installation is performed by root, because only root can write to the system directories and modify the database of installed packages. With very few exceptions (setuid or setgid programs), when you run the program, it runs with exactly the same privileges you already have — because “your privileges” actually means “the privileges of the processes that are running in your session”.

sudo: ./install: command not found.

I also tried running gksu ./install in which case it asks for my password in a separate window and then proceeds to do nothing. I just see the terminal with nothing going on. Can anyone tell me how I can run the install as root?

EDIT: Something weird may be going on. When I do ls I see the correct contents of the mounted disk. Then when I start typing sudo inst and press tab to autocomplete I see a list of files that are not in the mounted disk. Perhaps in some deeper

EDIT2: ls output

activate.ini  help                  install_guide.pdf  readme.txt
archives      install               java               sys
bin           installer_input.txt   license.txt        trademarks.txt    
etc           InstallForMacOSX.app  patents.txt        version.txt

EDIT3: its a christmas miracle, it works! I added the command exec to mount as exucutive and then did su — in the terminal and proceeded to install with no problems. Thanks so much everybody!

asked Mar 3, 2012 at 17:25

To become actually root:

sudo su

To HAVE a root account:

sudo passwd root 

(then type a new password, and that will be your new root account’s password.)

answered Mar 3, 2012 at 17:28

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On every Linux system, there is a root account. It’s safer to not use it for everyday tasks though, because careless typos on the command shell or bugs in software could otherwise seriously mess up your system.

By running sudo passwd, you can set a password for root if you really need it, but it’s likely that you don’t and will just invite accidents like accidental file deletions.

answered Mar 3, 2012 at 18:45

Daniel Beck

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If you need a root shell for a longer time you could use the -s option with the sudo command:

sudo -s

to create a permanent root shell. And type

exit

to leave the root shell when you’re done with your work.

answered Mar 3, 2012 at 18:34

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Let’s start with a bit of theory, to give you the context, and then I’ll show you how to enable root if you really want it, either in a terminal or even for SSH usage.

Is there a root user on Ubuntu Server?

The “root” still exists on Ubuntu Server and most Linux distributions, but can’t be used by default. The account is disabled for security reasons.

Why is the root user disabled on Ubuntu?

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Sudo: a better way to run root commands

You can basically do everything with sudo, so, in theory, there is no need to use “root” anymore.

What is the root password on Ubuntu Server?

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Use the exit command to get back to your normal privileges.
exit

I have explained that using “sudo” should be sufficient in most cases and that you can even temporarily switch to the root prompt in a terminal by using “sudo su”. You shouldn’t need anything more, but let’s discuss how to enable root if you really want to do this (not recommended).

Enable root login on Ubuntu Server

Before using the “root” account directly on Ubuntu Server, a password should be set via the command:
sudo passwd

As explained previously, having root enabled on your system is a major security issue, so at least try to use a strong password for it. Length is key, using a password generator like this one can help you to get something long enough but easy to remember.

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Here is how to allow logging in as root via SSH:

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Additional Resources

Lost with the command line?
You don’t need to learn and remember everything, just download my cheat sheet where I explain the most important commands on Linux, with a brief explanation and some examples.
Download my free PDF cheat sheet.

tar -xvzf root_v6.10.04.source.tar.gz root-6.10.04/

sudo apt-get install git dpkg-dev cmake g++ gcc binutils libx11-dev libxpm-dev libxft-dev libxext-dev

sudo apt-get install gfortran libssl-dev libpcre3-dev \
xlibmesa-glu-dev libglew1.5-dev libftgl-dev \
libmysqlclient-dev libfftw3-dev libcfitsio-dev \
graphviz-dev libavahi-compat-libdnssd-dev \
libldap2-dev python-dev libxml2-dev libkrb5-dev \
libgsl0-dev libqt4-dev

mkdir root
cd root

cmake ../root-6.10.04/ -Dall=ON

cmake --build . -- -j3

. bin/thisroot.sh

root

.q

pwd

/home/anil/Products/root

gedit ~/.bashrc

# For ROOT

export ROOTSYS=/home/anil/Products/root
export PATH=$ROOTSYS/bin:$PATH
export LD_LIBRARY_PATH=$ROOTSYS/lib/:$LD_LIBRARY_PATH

cmake ../root-6.18.04/

cmake ../root-6.18.04/ -Dminuit2=ON

mkdir root
cd root
cmake ../root-6.18.04/
make -j8
make install

Arch + Ubuntu 16.04 via Efi, Gpt, grub2

sda1                  -> efi boot
sda2                  -> encrypted, lvm on top
dev/mapper/vg-arch    -> my arch linux
dev/mapper/vg-ubuntu  -> my ubuntu installation

Arch is running fine. After the ubuntu installation I updated grub, so both are now bootable.

Problem: after booting into Ubuntu, I get the error:

root device mounted successfully, but /sbin/init does not exist ubuntu

/etc/default/grub

GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR='lsb_release -i -s 2> /dev/null || echo Debian'
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX="cryptdevice=/dev/sda2/luksvg"

grub-mkconfig -o /boot/grub/grub.cfg
grub-install --target=x86_64-efi --efi-directory=/boot --recheck

grub.cfg

# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#
### BEGIN /etc/grub.d/00_header ###
insmod part_gpt
insmod part_msdos
if [ -s $prefix/grubenv ]; then
  load_env
fi
if [ "${next_entry}" ] ; then
   set default="${next_entry}"
   set next_entry=
   save_env next_entry
   set boot_once=true
else
   set default="0"
fi

if [ x"${feature_menuentry_id}" = xy ]; then
  menuentry_id_option="--id"
else
  menuentry_id_option=""
fi

export menuentry_id_option

if [ "${prev_saved_entry}" ]; then
  set saved_entry="${prev_saved_entry}"
  save_env saved_entry
  set prev_saved_entry=
  save_env prev_saved_entry
  set boot_once=true
fi

function savedefault {
  if [ -z "${boot_once}" ]; then
    saved_entry="${chosen}"
    save_env saved_entry
  fi
}

function load_video {
  if [ x$feature_all_video_module = xy ]; then
insmod all_video
  else
    insmod efi_gop
    insmod efi_uga
    insmod ieee1275_fb
    insmod vbe
    insmod vga
    insmod video_bochs
    insmod video_cirrus
  fi
}

if loadfont unicode ; then
  set gfxmode=auto
  load_video
  insmod gfxterm
  set locale_dir=$prefix/locale
  set lang=de_DE
  insmod gettext
fi
terminal_input console
terminal_output gfxterm
if [ x$feature_timeout_style = xy ] ; then
  set timeout_style=menu
  set timeout=5
# Fallback normal timeout code in case the timeout_style feature is
# unavailable.
else
  set timeout=5
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/10_linux ###
menuentry 'Arch Linux' --class arch --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    load_video
    set gfxpayload=keep
    insmod gzio
    insmod part_gpt
    insmod fat
    set root='hd0,gpt1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1     --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  9E14-B35F
    else
  search --no-floppy --fs-uuid --set=root 9E14-B35F
    fi
    echo    'Linux linux wird geladen …'
    linux   /vmlinuz-linux root=/dev/mapper/luksvg-arch rw     cryptdevice=/dev/sda2:luksvg quiet
    echo    'Initiale Ramdisk wird geladen …'
    initrd  /initramfs-linux.img
}
submenu 'Erweiterte Optionen für Arch Linux'     $menuentry_id_option     'gnulinux-advanced-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    menuentry 'Arch Linux, mit Linux linux' --class arch --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-linux-    advanced-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    load_video
    set gfxpayload=keep
    insmod gzio
    insmod part_gpt
    insmod fat
    set root='hd0,gpt1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1     --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  9E14-B35F
    else
      search --no-floppy --fs-uuid --set=root 9E14-B35F
    fi
    echo    'Linux linux wird geladen …'
    linux   /vmlinuz-linux root=/dev/mapper/luksvg-arch rw     cryptdevice=/dev/sda2:luksvg quiet
    echo    'Initiale Ramdisk wird geladen …'
    initrd  /initramfs-linux.img
}
menuentry 'Arch Linux, with Linux linux (fallback initramfs)'     --class arch --class gnu-linux --class gnu --class os     $menuentry_id_option 'gnulinux-linux-fallback-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    load_video
    set gfxpayload=keep
    insmod gzio
    insmod part_gpt
    insmod fat
    set root='hd0,gpt1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1     --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  9E14-B35F
    else
      search --no-floppy --fs-uuid --set=root 9E14-B35F
    fi
    echo    'Linux linux wird geladen …'
    linux   /vmlinuz-linux root=/dev/mapper/luksvg-arch rw cryptdevice=/dev/sda2:luksvg quiet
        echo    'Initiale Ramdisk wird geladen …'
        initrd  /initramfs-linux-fallback.img
    }
}

### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_linux_xen ###
### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/30_os-prober ###
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f  ${config_directory}/custom.cfg ]; then
  source ${config_directory}/custom.cfg
elif [ -z "${config_directory}" -a -f  $prefix/custom.cfg ]; then
  source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###

so I thought maybe I have to set hooks in Ubuntu like I did in arch /etc/mkinitcpio.conf, but how?

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There are no such things as «stupid» questions. However if you think your question is a bit stupid, then this is the right place for you to post it. Please stick to easy to-the-point questions that you feel people can answer fast. For long and complicated questions prefer the other forums within the support section.
Before you post please read how to get help. Topics in this forum are automatically closed 6 months after creation.

Installing a program as root

I am not a COMPLETE noob, since I’ve installed Mint on several machines, but this one is a problem.

New NVIDIA driver updates keep telling me that they must be installed as «root». I’ve searched the web and forums and all I can find is people telling me NEVER to run, or install anything, as root. Apparently it’s just not supposed to be done, and no one will SAY how to do it because it’s too dangerous.

I tried myself to go to the Login Window Preferences and under Options selected «Allow Root Login», but that doesn’t seem to do a thing.

So, how does one install new driver updates?

Last edited by LockBot on Wed Dec 28, 2022 7:16 am, edited 1 time in total.

Reason: Topic automatically closed 6 months after creation. New replies are no longer allowed.

Re: Installing a program as root

by » Mon Jan 02, 2017 4:46 pm

The only driver that appears there is .132 which is 2D. I downloaded .134 from NVIDIA for 3D graphics in order to run X-Plane 10.

The installation worked fine on a computer I built from a motherboard with a GTX-650 graphics card, but now I’m trying to install on an older HP Pavilion laptop with the NVIDIA C67 card. When I run the program, it hangs trying to initialize OpenGL. It may just be the card.

jimallyn

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Posts: 9075

Joined: Thu Jun 05, 2014 7:34 pm

Location: Wenatchee, WA USA

Re: Installing a program as root

by jimallyn » Mon Jan 02, 2017 5:18 pm

I agree with MintBean, the best way to install drivers is with Mint’s Driver Manager. If you want the newest version, you may have to install from Nvidia’s latest release. Try this: open a terminal, navigate to wherever you have saved the driver file, then enter sudo NVIDIA-Linux-x86_64-304.134.run. That will ask for your password, then will run the installer as root. Note: it is possible that this could screw up your video and make it impossible to boot into the GUI. I had that happen once, and had to boot to terminal and remove the drivers from there, then reboot. Let’s hope that doesn’t happen, but if it does, people on the forums can almost surely walk you through it.

“If the government were coming for your TVs and cars, then you’d be upset. But, as it is, they’re only coming for your sons.” — Daniel Berrigan

Re: Installing a program as root

by » Mon Jan 02, 2017 5:19 pm

The recommended driver is for GeForce7 series cards, which appears to be what you have from a quick Google or am I mistaken? I’ve never heard of this concept of a driver for 2D and a separate driver for 3D — are you sure you have this straight?

If you’re running the Mint Cinnamon edition and it’s not complaining about running in software rendering mode, you’re running in 3D accelerated mode.

Open a terminal (Applications->Accessories->Terminal).

if step 4 fails with a message including ‘permission denied’, try entering sudo ./some-app.run (you will need to enter your password for this).

karlchen

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Posts: 17344

Joined: Sat Dec 31, 2011 7:21 am

Location: Germany

Re: Installing a program as root

by karlchen » Mon Jan 02, 2017 5:29 pm

This must be some kind of misunderstanding: software which is installed system-wide is always installed with root privileges, no matter whether you use Software Manager, Synaptic or an apt-get commandline. The same is also true if you install software system-wide manually; you will do so with root privileges.

So in order to install the downloaded NVidia driver software you would proceed like this:

• cd /path/to/folder/where/you/saved/the_file
• chmod +x NVIDIA-Linux-x86_64-304.134.run
• sudo ./NVIDIA-Linux-x86_64-304.134.run

Re: Installing a program as root

by » Mon Jan 02, 2017 5:30 pm

Still working on it. I scrapped the HD and re-loaded Mint MATE instead of Cinnamon. Now I get the NVIDIA .132 drivers to load (which WERE on the driver updater) without crashing Cinnamon. MATE seems to be better at accepting the «recommended» drivers.

karlchen

Level 22

Posts: 17344

Joined: Sat Dec 31, 2011 7:21 am

Location: Germany

Re: Installing a program as root

by karlchen » Mon Jan 02, 2017 5:39 pm

Cinnamon insists on having 3D hardware acceleration. Mate does not. This is why some problems with video driver software will be encountered on Cinnamon desktops only.

Re: Installing a program as root

by » Mon Jan 02, 2017 5:47 pm

Ahah! And I need 3D capability for X-Plane. That why it WILL run on my other computer using Cinnamon with the GTX card. It MUST be the drivers for this HP laptop then that are the problem. So now I need to find some way of installing the .124 drivers from NVIDIA without having to install as root.

If I was smarter and already KNEW how to run as root, this whole thing would have been over 12 hours ago.

Re: Installing a program as root

by » Mon Jan 02, 2017 5:49 pm

Mate was not working anyhow. I downloaded the DVD drivers from X-Plane and keep getting «BadValue» and «Major Opcode Failed» errors. I’m off to scrape the drive again and return to Cinnamon.

austin.texas

Level 20

Posts: 12003

Joined: Tue Nov 17, 2009 3:57 pm

Location: at /home

Re: Installing a program as root

by austin.texas » Mon Jan 02, 2017 5:51 pm

flaugher wrote: I’ve searched the web and forums and all I can find is people telling me NEVER to run, or install anything, as root. Apparently it’s just not supposed to be done, and no one will SAY how to do it because it’s too dangerous.

Mint 18.2 Cinnamon, Quad core AMD A8-3870 with Radeon HD Graphics 6550D, 8GB DDR3, Ralink RT2561/RT61 802.11g PCI
Linux Linx 2018

Re: Installing a program as root

by » Mon Jan 02, 2017 5:55 pm

Well, see, that’s what I THOUGHT to begin with. I usually install things using ./ which normally works fine. I think the REAL problem is that I’m an Aggie! Woo-ahh! (I wish they had a maroon icon)

austin.texas

Level 20

Posts: 12003

Joined: Tue Nov 17, 2009 3:57 pm

Location: at /home

Re: Installing a program as root

by austin.texas » Mon Jan 02, 2017 6:04 pm

flaugher wrote: I think the REAL problem is that I’m an Aggie! Woo-ahh! (I wish they had a maroon icon)

Happy New Year!

Mint 18.2 Cinnamon, Quad core AMD A8-3870 with Radeon HD Graphics 6550D, 8GB DDR3, Ralink RT2561/RT61 802.11g PCI
Linux Linx 2018

su -c 'service apache restart'

The command to run must be passed using the -c option. Note that you need quotes so that the command is not parsed by your shell, but passed intact to the root shell that su runs.

To run multiple commands as root, it is more convenient to start an interactive shell.

$ su
# command 1
# command 2
...
# exit

On some systems, you need to be in group number 0 (called wheel) to use su. (The point is to limit the damage if the root password is accidentally leaked to someone.)

How to install sudo

In most of the Linux distributions, sudo is pre-installed on the system. However, if you do not find the sudo package on the system, you can install it from the default package management repositories.

To install sudo on CentOS, Fedora, and RHEL

# yum install sudo

To install sudo on Ubuntu and Debian

# apt install sudo

Syntax for sudo command

Some of the options available in sudo command are:

• -V: display version information of sudo
• -h: display help message and exit
• -l: list user’s privileges or check a specific command
• -k: reset the user’s timestamp
• -u: run the command as a different user

Editing a file as root

See How do I edit a file as root?

How to build binaries as a non-root

./configure --prefix=$HOME && make && make install

answered Feb 18, 2014 at 15:07

Another option is to install from source, where you can usually change the install directory using the --prefix switch.

answered Nov 13, 2010 at 15:38

John T

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There are clever tricks to help you in the manual build process. For example, you can utilize the dependencies already listed in an RPM to get all of your dependencies: https://stackoverflow.com/a/13877738/1236128.

answered Oct 21, 2019 at 7:18

You can try --prefix and --dbpath options. Not all RPMs will support --prefix, but if your rolling your own RPMs that won’t be an issue, just make them relocatable.

rpm -ivh --dpath ~/rpmdb --prefix ~/ mypkg-1.0-1.el8.x86_64.rpm

You could also ask your IT to make the system RPM DB writable.

Also answered here How to install packages on Linux without root-access?

answered Jun 25, 2022 at 5:14

Running a graphical command as root

See also Wikipedia.

PolicyKit (preferred when using GNOME)

Simply prefix your desired command with the command pkexec. Be aware that while this works in most cases, it does not work universally.

KdeSu, KdeSudo (preferred when using KDE)

kdesu and kdesudo are graphical front-ends to su and sudo respectively. They allow you to run X Window programs as root with no hassle. They are part of KDE. Type

kdesu -c 'command --option argument'

and enter the root password, or type

kdesudo -c 'command --option argument'

and enter your password (if authorized to run sudo). If you check the “keep password” option in KdeSu, you will only have to type the root password once per login session.

Other programs

Ktsuss (“keep the su simple, stupid”) is a graphical version of su.

Beesu is a graphical front-end to the su command that has replaced Gksu in Red Hat-based operating systems. It has been developed mainly for RHEL and Fedora.

Obsolete methods

gksu and gksudo

gksu and gksudo are graphical front-ends to su and sudo respectively. They allow you to run X Window programs as root with no hassle. They are part of Gnome. Type

gksu command --option argument

and enter the root password, or type

gksudo command --option argument

and enter your password (if authorized to run sudo).

gksu and gksudo are obsolete. They have been replaced by PolicyKit in GNOME, and many distributions (such as Ubuntu) no longer install them by default. You should not depend on them being available or working properly.

Manually via one of the shell-based methods

Use one of the methods in the «running a shell command as root section». You will need to ensure that neither the DISPLAY environment variable nor the XAUTHORITY environment get reset during the transition to root. This may require additional configuration of those methods that is outside the scope of this question.

Further Reading

man page for sudo command

Different examples to use sudo command

1. Use sudo to run command as a root user

$ sudo command

2. Use sudo to run command as a different user

golinux@ubuntu-PC:~$ sudo -u deepak whoami

golinux@ubuntu-PC:~$ sudo passwd deepak 
New password: 
Retype new password: 
passwd: password updated successfully

3. List user privileges with sudo command

$ sudo -l

$ sudo --list

deepak@ubuntu:~$ sudo -l

Use -l twice for longer output:

deepak@ubuntu:~$ sudo -ll
Matching Defaults entries for deepak on ubuntu:
    env_reset, mail_badpass,
    secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin

User deepak may run the following commands on ubuntu:

Sudoers entry:

As you can see, it does not run the command but only checks where it is located in the system.

golinux@ubuntu-PC:~$ sudo -l adduser

4. Display privileges for another user with sudo command

5. sudo command to add a user to the sudo group

On RHEL, CentOS, and Fedora, you can use:

6. sudo command to add users to the sudoers file

$ sudo visudo

7. Run command in the background with sudo

The -b or --background option can be used to run the given command in the background. When you use this option, you cannot use shell job control to manipulate the process.

$ sudo -b command

$ sudo --background command

8. Update sudoers files using sudo command

$ sudo -e file

$ sudo --edit file

You can only edit files on the directory which is non-writable. It opens a nano editor to edit a file.

$ sudo -e /etc/sudoers.d/01-sudo-rule

deepak@ubuntu:~$ sudo -e /etc/sudoers.d/01-sudo-rule
>>> /etc/sudoers.d/01-sudo-ssh: syntax error near line 2 <<<
sudo: parse error in /etc/sudoers.d/01-sudo-rule near line 2
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

9. sudo command to update the user’s cached credentials

$ sudo -v

$ sudo --validate

golinux@ubuntu-PC:~$ sudo -v
[sudo] password for golinux:

10. sudo command to invalidate user’s cached credentials

$ sudo -k 

$ sudo --reset-timestamp

11. sudo command to remove the user’s timestamp completely

$ sudo -K

$ sudo --remove-timestamp

How to extract tar. gz packages to the current directory

export file=foo-bar.tar.gz
# Note that `xovf` switch order *matters*
gzip -dc $file | tar -xovf -

How to extract rpm packages contents

export ins=foo-bar.rpm
rpm2cpio $ins | cpio -idv

Other programs

Calife

Op

Super

How to extract tar. gz archive

gzip -dc foo-bar.tar.gz | tar xvf –
cd foo-bar-dir

Logging in as root

If there is a root password set and you are in possession of it, you can simply type root at the login prompt and enter the root password. Be very careful, and avoid running complex applications as root as they might do something you didn’t intend. Logging in directly as root is mainly useful in emergency situations, such as disk failures or when you’ve locked yourself out of your account.

Sudo (preferred when not running a graphical display)

This is the preferred method on most systems, including Ubuntu, Linux Mint, (arguably) Debian, and others. If you don’t know a separate root password, use this method.

Sudo requires that you type your own password. (The purpose is to limit the damage if you leave your keyboard unattended and unlocked, and also to ensure that you really wish to run that command and it wasn’t e.g. a typo.) It is often configured to not ask again for a few minutes so you can run several sudo commands in succession.

sudo service apache restart

If you need to run several commands as root, prefix each of them with sudo. Sometimes, it is more convenient to run an interactive shell as root. You can use sudo -i for that:

$ sudo -i
# command 1
# command 2
...
# exit

Instead of sudo -i, you can use sudo -s. The difference is that -i reinitializes the environment to sane defaults, whereas -s uses your configuration files for better or for worse.