Add another admin in Ubuntu server

There are several reasons why we need extra admin user in Ubuntu server. One of the reason perhaps it's an account for your boss. Yes, in several occasions, your boss needs root privilege to do whatever 'his job' that need to be done.

Well, whatever your reason is, here is how you can add another user in the admin group in Ubuntu server:

Login into Ubuntu server using user in admin group username(user with root privilege). This is the user that can use 'sudo' command, or the default user you created during Ubuntu server installation.

In the command prompt, type:

luzar@ubuntu:~$ sudo adduser jimi admin
Adding user `jimi' to group `admin' ...
Adding user jimi to group admin
Done.
luzar@ubuntu:~$

Replace jimi with a username that you want to add to the admin group. Let's check the /etc/group file to see whether the user has been added to the admin group:

luzar@ubuntu:~$ cat /etc/group

Here is the result:

luzar:x:1000:
lpadmin:x:112:
sambashare:x:113:
admin:x:114:luzar,jimi
programmer:x:1001:luzar
dhcpd:x:115:
jimi:x:1002:

That's it. Now jimi can run whatever commands that needs root privilege by using sudo command. He has the same power as you now.

How to check Ubuntu server Linux version

If you are a Windows user before, there is no ver command in Linux that can be used to check the version of Ubuntu server.  In  Linux  or  Ubuntu  server specifically, there are many commands that can be used to check operating system version.

The first command that can be used to check Ubuntu server version is, as Ubuntu suggest, the lsb_release -a command. Here is the example:

luzar@ubuntu:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 8.10
Release:        8.10
Codename:       intrepid
luzar@ubuntu:~$

Second command that we can use to check Linux version is cat /proc/version. See example below:

luzar@ubuntu:~$ cat /proc/version
Linux version 2.6.27-14-server (buildd@palmer) (gcc version 4.3.2 (Ubuntu 4.3.2-1ubuntu12) ) #1 SMP Wed Apr 15 19:44:38 UTC 2009
luzar@ubuntu:~$
 
We can also view all information about Ubuntu server using uname -a option:

luzar@ubuntu:~$ uname -a
Linux ubuntu 2.6.27-14-server #1 SMP Wed Apr 15 19:44:38 UTC 2009 i686 GNU/Linux

There you go. We've got more information than what we ask for. Well, that's good, isn't it?

How to add user to a group in Linux operating system

We can assign user to a group during adding a new user account. But how do we add existing user to a group? This tutorial is a guide on how to add user to a new group. The right Linux command for the job is the usermod command.

This is some information about Linux usermod command from manual page:

NAME
       usermod - modify a user account

SYNOPSIS
       usermod [options] LOGIN

DESCRIPTION
       The usermod command modifies the system account files to reflect the
       changes that are specified on the command line.

As you can see, the Linux usermod command can be used to modify a user account. However in this tutorial, we'll only use usermod command to add user to a new group. For this example, we'll create a new group to practice. Use the groupadd command to create a new group:

luzar@ubuntu:~$ groupadd programmer
groupadd: unable to lock group file
luzar@ubuntu:~$ sudo groupadd programmer
[sudo] password for luzar:
luzar@ubuntu:~$

Don't forget to use sudo command in Ubuntu, else you'll get the groupadd: unable to lock group file error as in the example above. Check whether the programmer group has been created in /etc/group file:

luzar@ubuntu:~$ less /etc/group | grep programmer
programmer:x:1001:
luzar@ubuntu:~$

Next, we are going to add user to a new group. For this example, we are going to add a user called luzar to the programmer group. Below are step by step instructions.

Use usermod -G option to add user to a new group:

luzar@ubuntu:~# sudo usermod -G programmer luzar

Use Linux groups command to check whether the programmer group has been added to luzar's group:

luzar@ubuntu:~# groups luzar
luzar : users programmer
luzar@ubuntu:~#

As you can see, the user luzar now has programmer as a second group. We can also check /etc/group to verify user currently in the programmer group:

luzar@ubuntu:~$ less /etc/group | grep programmer
programmer:x:1001:luzar
luzar@ubuntu:~$

That's all.

How to mount external hard drive in Ubuntu server

This is a step by step guide on how to mount external hard drive in Linux for Ubuntu server beginner and Linux beginner in general. The guide includes error happened during the process to show how it to mount device in real situation.

Mount external hard drive in Ubuntu server

Insert external hard drive usb connector into the Ubuntu server usb port.  Ubuntu server automatically detect the external hard drive as a usb device. Below is the example screenshot when ubuntu detected the external hard drive:

 

We can see that the external hard drive has been detected as sdb. That is the name of the external hard drive to use when we are going to mount the device. We can check the device in /proc/scsi/scsi file. To do that, issue the command as in the example below:

luzar@ubuntu:~$ cat /proc/scsi/scsi
Attached devices:
Host: scsi1 Channel: 00 Id: 00 Lun: 00
  Vendor: NECVMWar Model: VMware IDE CDR10 Rev: 1.00
  Type:   CD-ROM                           ANSI  SCSI revision: 05
Host: scsi2 Channel: 00 Id: 00 Lun: 00
  Vendor: VMware,  Model: VMware Virtual S Rev: 1.0
  Type:   Direct-Access                    ANSI  SCSI revision: 02
Host: scsi3 Channel: 00 Id: 00 Lun: 00
  Vendor: Generic  Model: USB Disk         Rev: 9.02
  Type:   Direct-Access                    ANSI  SCSI revision: 02
luzar@ubuntu:~$

Create a proper directory in Ubuntu server to mount the external hard drive. In this example, we create a directory named extdisk in /mnt directory:

luzar@ubuntu:~$ sudo mkdir /mnt/extdisk
[sudo] password for luzar:
luzar@ubuntu:~$ ls /mnt/
dvd  extdisk  usb  win

Now we can mount the external hard drive with Linux mount command:

luzar@ubuntu:~$ sudo mount /dev/sdb /mnt/extdisk/
mount: you must specify the filesystem type

The external hard drive cannot be mounted. This happened when we mount a windows formatted external hard drive. We must specify the filesystem. Windows filesystem format is known as nsfs-3g in Linux. So we mount the external hard drive again with the complete command:

luzar@ubuntu:~$ sudo mount -t ntfs-3g /dev/sdb /mnt/extdisk/
NTFS signature is missing.
Failed to mount '/dev/sdb': Invalid argument
The device '/dev/sdb' doesn't have a valid NTFS.
Maybe you selected the wrong device? Or the whole disk instead of a
partition (e.g. /dev/hda, not /dev/hda1)? Or the other way around?

We still cannot mount the external hard drive. Again, we mount the external hard drive but this we change the device name from /dev/sdb to /dev/sdb1 as suggested by Ubuntu message above.

luzar@ubuntu:~$ sudo mount -t ntfs-3g /dev/sdb1 /mnt/extdisk/
luzar@ubuntu:~$ ls /mnt/extdisk/
ghost dell170l  ghost mimos  RECYCLER  System Volume Information
luzar@ubuntu:~$

We successfully mounted the external hard drive this time. Now that the external drive has been mounted, we can use it as other directory in Ubuntu.

To unmount the external hard drive, we can use the Linux umount command like in the example below:

luzar@ubuntu:~$ sudo umount /mnt/extdisk/
[sudo] password for luzar:
luzar@ubuntu:~$

That's all.

How to power off Ubuntu server with Linux shutdown command

The Linux shutdown command has several options that you can use to bring down the Linux system. In the previous post, we've seen how to reboot Ubuntu server with shutdown command. In this post,  we are going to use the Linux shutdown command again. This time is to power off the Ubuntu server.

There are several options available with shutdown command that can be used to power off Linux system. One example is -h option, which means to halt the system after it has been brought down. We can add other things such as a comment message when invoking shutdown -h command. As you can see from the example of Ubuntu restart post before, we have to specify a time argument after the shutdown option so the system know when to shutdown the system. Here are some examples on how to power off Ubuntu server using shutdown command with other things that you can do:

1) Using Linux shutdown command with -h option example:

luzar@ubuntu:~$ sudo shutdown -h now
[sudo] password for luzar:

Broadcast message from luzar@ubuntu
        (/dev/pts/0) at 11:32 ...

The system is going down for halt NOW!

The example above show a basic shutdown command used to power off Ubuntu server. We used '-h' option and a time argument 'now' which means to bring down the system after we press enter.

 2) Using Linux shutdown command -p option example:

luzar@ubuntu:~$ sudo shutdown -h -P +1

Broadcast message from luzar@ubuntu
        (/dev/pts/0) at 11:47 ...

The system is going down for power off IN ONE MINUTE! 

The example above shows the '-P' option is added after the '-h' option. The -P option means 'power off'. When -P is used after -h option, it means we tell the system to power off after the system halt. Also this time we used +1 in the time argument. That means we want to bring down the system after 1 minute.

3) If you have to warn all your users, you can write a message after the time argument. See the example below:

luzar@ubuntu:~$ sudo shutdown -h -P +3 Please save your work now!

Broadcast message from luzar@ubuntu
        (/dev/pts/0) at 11:57 ...

The system is going down for power off in 3 minutes!
Please save your work now!
shutdown: Shutdown cancelled

If you want to cancel shutdown after invoked the command, you can press Ctrl+C combination keys. That will work if you do not use the 'now' time argument. If you just want to warn users to log out and prevent other user to login without actually bring the system down, you can use '-k' option.

luzar@ubuntu:~$ sudo shutdown -k +3 Please save your work now!

Broadcast message from luzar@ubuntu
        (/dev/pts/0) at 12:11 ...

The system is going down for maintenance in 3 minutes!
Please save your work now!
luzar@ubuntu:~$

That's all.