Andromeda Computer - Blog
Ilich Blanco

Ilich Blanco

Entusiasta de la naturaleza y apasionado de la tecnología desde que puedo recordar, inversionista y fiel creyente de la tecnología blockchain y criptomonedas. Estoy seguro que los problemas de la sociedad y la humanidad en general no serán resueltos por economistas o sociólogos si no por la mente brillante de científicos.
Website URL: http://https://www.linkedin.com/in/ilichblanco Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Friday, 16 August 2019 19:35

GNOME desktop: Best extensions

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Add functionality and features to your Linux desktop with these add-ons.

 

The GNOME desktop is the default graphical user interface for most of the popular Linux distributions and some of the BSD and Solaris operating systems. Currently at version 3, GNOME provides a sleek user experience, and extensions are available for additional functionality. We've covered GNOME extensions before, but to celebrate GNOME's 22nd anniversary, I decided to revisit the topic. Some of these extensions may already be installed, depending on your Linux distribution; if not, check your package manager.

 

 How to add extensions from the package manager
To install extensions that aren't in your distro, open the package manager and click Add-ons. Then click Shell Extensions at the top-right of the Add-ons screen, and you will see a button for Extension Settings and a list of available extensions.

  

To install extensions that aren't in your distro, open the package manager and clic Then clic Shell Extensions at the top-right of the Add-ons screen, and you will see a button for Extension Settings and a list of available extensions.

add-onsextensions_6.png

 

1. GNOME Clocks

GNOME Clocks is an application that includes a world clock, alarm, stopwatch, and timer. You can configure clocks for different geographic locations. For example, if you regularly work with colleagues in another time zone, you can set up a clock for their location. You can access the World Clocks section in the top panel's drop-down menu by clicking the system clock. It shows your configured world clocks (not including your local time), so you can quickly check the time in other parts of the world.

 

 

2. GNOME Weather

GNOME Weather displays the weather conditions and forecast for your current location. You can access local weather conditions from the top panel's drop-down menu. You can also check the weather in other geographic locations using Weather's Places menu.

 clocksweatherdropdown_6.png

 

GNOME Clocks and Weather are small applications that have extension-like functionality. Both are installed by default on Fedora 30 (which is what I'm using). If you're using another distribution and don't see them, check the package manager. You can see both extensions in action in the image below.

clocksweatherdropdown_6.png

3. Applications Menu
I think the GNOME 3 interface is perfectly enjoyable in its stock form, but you may prefer a traditional application menu. In GNOME 30, the Applications Menu extension was installed by default but not enabled. To enable it, click the Extensions Settings button in the Add-ons section of the package manager and enable the Applications Menu extension.

add-onsextensionsettings_6.png

Now you can see the Applications Menu in the top-left corner of the top panel.

 applicationsmenuextension_5.png

4. More columns in applications view
The Applications view is set by default to six columns of icons, probably because GNOME needs to accommodate a wide array of displays. If you're using a wide-screen display, you can use the More columns in applications menu extension to increase the columns. I find that setting it to eight makes better use of my screen by eliminating the empty columns on either side of the icons when I launch the Applications view.

Add system info to the top panel
The next three extensions provide basic system information to the top panel.

5. Harddisk LED shows a small hard drive icon with input/output (I/O) activity.
6. Load Average indicates Linux load averages taken over three time intervals.
7. Uptime Indicator shows system uptime; when it's clicked, it shows the date and time the system was started.

 

8. Sound Input and Output Device Chooser
Your system may have more than one audio device for input and output. For example, my laptop has internal speakers and sometimes I use a wireless Bluetooth speaker. The Sound Input and Output Device Chooser extension adds a list of your sound devices to the System Menu so you can quickly select which one you want to use.

9. Drop Down Terminal
Fellow writer Scott Nesbitt recommended the next two extensions. The first, Drop Down Terminal, enables a terminal window to drop down from the top panel by pressing a certain key; the default is the key above Tab; on my keyboard, that's the tilde (~) character. Drop Down Terminal has a settings menu for customizing transparency, height, the activation keystroke, and other configurations.

10. Todo.txt
Todo.txt adds a menu to the top panel for maintaining a file for Todo.txt task tracking. You can add or delete a task from the menu or mark it as completed.

todo.txtmenu_3.png

11. Removable Drive Menu
the editor Seth Kenlon suggested Removable Drive Menu. It provides a drop-down menu for managing removable media, such as USB thumb drives. From the extension's menu, you can access a drive's files and eject it. The menu only appears when removable media is inserted.

removabledrivemenu_3.png

 

12. GNOME Internet Radio
I enjoy listening to internet radio streams with the GNOME Internet Radio extension, which I wrote about in How to Stream Music with GNOME Internet Radio.

 

please read more at opensource.com

 

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Wednesday, 14 August 2019 11:31

Fantastic Tattoos: Naruto and Naruto Shippuden

 

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Hello everyone otakus and not otakus, the important thing is that they appreciate art. This time I want to share with you this super collection of Naruto tattoos! yes ... They are the best tattoos you will see dedicated to this great anime.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Tuesday, 06 August 2019 23:01

Fantastic Tattoos: Shingueki No Kyojin

It is one of the most popular anime of the moment, with a complicated plot, fantastic and characters with complicated and moving stories shigeki no kyojin inspires thousands of artists and fans around the world. In this occasion we will show you the most incredible tattoos of this fabulous anime.

 

 

1f28edc3031d9d9e8dc1a8fcbfd55b7a3d21b89a hq

 

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31706c7fad2d43ee2ef82dcf6f7425b5

 

 

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43375152 315593839234751 178875917791482764 n

 

 

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61074910 1298654776966297 7437632794112953660 n

 

61401718 370008620387090 89764174817401407 n

 

61923148 155564745490946 1170008567332178557 n

 

62247087 471468710330336 3584156933197092643 n

 

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65832120 2420633991491848 3843082408706315079 n

 

 

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BANNERGnulinuxrocks

 

Linux is fully capable of running not weeks, but years, without a reboot. In some industries, that’s exactly what Linux does, thanks to advances like kpatch and kgraph.

For laptop and desktop users, though, that metric is a little extreme. While it may not be a day-to-day reality, it’s at least a weekly reality that sometimes you have a good reason to reboot your machine. And for a system that doesn’t need rebooting often, Linux offers plenty of choices for when it’s time to start over.

 

 

Understand your options

Before continuing though, a note on rebooting. Rebooting is a unique process on each operating system. Even within POSIX systems, the commands to power down and reboot may behave differently due to different initialization systems or command designs.

Despite this factor, two concepts are vital. First, rebooting is rarely requisite on a POSIX system. Your Linux machine can operate for weeks or months at a time without a reboot if that’s what you need. There’s no need to "freshen up" your computer with a reboot unless specifically advised to do so by a software installer or updater. Then again, it doesn’t hurt to reboot, either, so it’s up to you.

Second, rebooting is meant to be a friendly process, allowing time for programs to exit, files to be saved, temporary files to be removed, filesystem journals updated, and so on. Whenever possible, reboot using the intended interfaces, whether in a GUI or a terminal. If you force your computer to shut down or reboot, you risk losing unsaved and even recently-saved data, and even corrupting important system information; you should only ever force your computer off when there’s no other option.

 

 

Click the button

The first way to reboot or shut down Linux is the most common one, and the most intuitive for most desktop users regardless of their OS: It’s the power button in the GUI. Since powering down and rebooting are common tasks on a workstation, you can usually find the power button (typically with reboot and shut down options) in a few different places. On the GNOME desktop, it's in the system tray: 

gnome-menu-power.jpg

It’s also in the GNOME Activities menu:

gnome-screen-power.jpg

On the KDE desktop, the power buttons can be found in the Applications menu:

kde-menu-power.jpg

You can also access the KDE power controls by right-clicking on the desktop and selecting the Leave option, which opens the window you see here:

kde-screen-power.jpg

Other desktops provide variations on these themes, but the general idea is the same: use your mouse to locate the power button, and then click it. You may have to select between rebooting and powering down, but in the end, the result is nearly identical: Processes are stopped, nicely, so that data is saved and temporary files are removed, then data is synchronized to drives, and then the system is powered down.

 

 

Push the physical button

Most computers have a physical power button. If you press that button, your Linux desktop may display a power menu with options to shut down or reboot. This feature is provided by the Advanced Configuration and Power Interface (ACPI) subsystem, which communicates with your motherboard’s firmware to control your computer’s state.

ACPI is important but it’s limited in scope, so there’s not much to configure from the user’s perspective. Usually, ACPI options are generically called Power and are set to a sane default. If you want to change this setup, you can do so in your system settings.

On GNOME, open the system tray menu and select Activities, and then Settings. Next, select the Power category in the left column, which opens the following menu:

gnome-settings-power.jpg

In the Suspend & Power Button section, select what you want the physical power button to do.

The process is similar across desktops. For instance, on KDE, the Power Management panel in System Settings contains an option for Button Event Handling.

 

kde-power-management.jpg

After you configure how the button event is handled, pressing your computer’s physical power button follows whatever option you chose. Depending on your computer vendor (or parts vendors, if you build your own), a button press might be a light tap, or it may require a slightly longer push, so you might have to do some tests before you get the hang of it.

Beware of an over-long press, though, since it may shut your computer down without warning.

 

 

Run the systemctl command

If you operate more in a terminal than in a GUI desktop, you might prefer to reboot with a command. Broadly speaking, rebooting and powering down are processes of the init system—the sequence of programs that bring a computer up or down after a power signal (either on or off, respectively) is received.

On most modern Linux distributions, systemd is the init system, so both rebooting and powering down can be performed through the systemd user interface, systemctl. The systemctl command accepts, among many other options, halt (halts disk activity but does not cut power) reboot (halts disk activity and sends a reset signal to the motherboard) and poweroff (halts disk acitivity, and then cut power). These commands are mostly equivalent to starting the target file of the same name.

For instance, to trigger a reboot:

sudo systemctl start reboot.target

 

Run the shutdown command

Traditional UNIX, before the days of systemd (and for some Linux distributions, like Slackware, that’s now), there were commands specific to stopping a system. The shutdown command, for instance, can power down your machine, but it has several options to control exactly what that means.

This command requires a time argument, in minutes, so that shutdown knows when to execute. To reboot immediately, append the -r flag:

sudo shutdown -r now

To power down immediately:

sudo shutdown -P now

Or you can use the poweroff command:

poweroff

To reboot after 10 minutes:

sudo shutdown -r 10

The shutdown command is a safe way to power off or reboot your computer, allowing disks to sync and processes to end. This command prevents new logins within the final 5 minutes of shutdown commencing, which is particularly useful on multi-user systems.

On many systems today, the shutdown command is actually just a call to systemctl with the appropriate reboot or power off option.

 

Run the reboot command

The reboot command, on its own, is basically a shortcut to shutdown -r now. From a terminal, this is the easiest and quickest reboot command:

sudo reboot

If your system is being blocked from shutting down (perhaps due to a runaway process), you can use the --force flag to make the system shut down anyway. However, this option skips the actual shutting down process, which can be abrupt for running processes, so it should only be used when the shutdowncommand is blocking you from powering down.

On many systems, reboot is actually a call to systemctl with the appropriate reboot or power off option.

 

Init

On Linux distributions without systemd, there are up to 7 runlevels your computer understands. Different distributions can assign each mode uniquely, but generally, 0 initiates a halt state, and 6 initiates a reboot (the numbers in between denote states such as single-user mode, multi-user mode, a GUI prompt, and a text prompt).

These modes are defined in /etc/inittab on systems without systemd. On distributions using systemd as the init system, the /etc/inittab file is either missing, or it’s just a placeholder.

The telinit command is the front-end to your init system. If you’re using systemd, then this command is a link to systemctl with the appropriate options.

To power off your computer by sending it into runlevel 0:

sudo telinit 0

To reboot using the same method:

sudo telinit 6

How unsafe this command is for your data depends entirely on your init configuration. Most distributions try to protect you from pulling the plug (or the digital equivalent of that) by mapping runlevels to friendly commands.

You can see for yourself what happens at each runlevel by reading the init scripts found in /etc/rc.d or /etc/init.d, or by reading the systemd targets in /lib/systemd/system/.

 

Apply brute force

So far I’ve covered all the right ways to reboot or shut down your Linux computer. To be thorough, I include here additional methods of bringing down a Linux computer, but by no means are these methods recommended. They aren’t designed as a daily reboot or shut down command (reboot and shutdown exist for that), but they’re valid means to accomplish the task.

If you try these methods, try them in a virtual machine. Otherwise, use them only in emergencies.

 

 

Proc

A step lower than the init system is the /proc filesystem, which is a virtual representation of nearly everything happening on your computer. For instance, you can view your CPUs as though they were text files (with cat /proc/cpuinfo), view how much power is left in your laptop’s battery, or, after a fashion, reboot your system.

There’s a provision in the Linux kernel for system requests (Sysrq on most keyboards). You can communicate directly with this subsystem using key combinations, ideally regardless of what state your computer is in; it gets complex on some keyboards because the Sysrq key can be a special function key that requires a different key to access (such as Fn on many laptops).

An option less likely to fail is using echo to insert information into /proc, manually. First, make sure that the Sysrq system is enabled:

sudo echo 1 > /proc/sys/kernel/sysrq

To reboot, you can use either Alt+Sysrq+B or type:

sudo echo b > /proc/sysrq-trigger

This method is not a reasonable way to reboot your machine on a regular basis, but it gets the job done in a pinch.

 

Sysctl

Kernel parameters can be managed during runtime with sysctl. There are lots of kernel parameters, and you can see them all with sysctl --all. Most probably don’t mean much to you until you know what to look for, and in this case, you’re looking for kernel.panic.

You can query kernel parameters using the -–value option:

sudo sysctl --value kernel.panic

 

If you get a 0 back, then the kernel you’re running has no special setting, at least by default, to reboot upon a kernel panic. That situation is fairly typical since rebooting immediately on a catastrophic system crash makes it difficult to diagnose the cause of the crash. Then again, systems that need to stay on no matter what might benefit from an automatic restart after a kernel failure, so it’s an option that does get switched on in some cases.

You can activate this feature as an experiment (if you’re following along, try this in a virtual machine rather than on your actual computer

 

sudo sysctl kernel.reboot=1

 

Now, should your computer experience a kernel panic, it is set to reboot instead of waiting patiently for you to diagnose the problem. You can test this by simulating a catastrophic crash with sysrq. First, make sure that Sysrq is enabled:

 

sudo echo 1 > /proc/sys/kernel/sysrq

And then simulate a kernel panic:

sudo echo c > /proc/sysrq-trigger

Your computer reboots immediately.

 

Reboot responsibly

Knowing all of these options doesn't mean that you should use them all. Give careful thought to what you're trying to accomplish, and what the command you've selected will do. You don't want to damage your system by being reckless. That's what virtual machines are for. However, having so many options means that you're ready for most situations.

Have I left out your favorite method of rebooting or powering down a system? List what I’ve missed in the comments!

 

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 Source: opensource.com Please visit and support the linux project.

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Wednesday, 17 July 2019 23:40

The man who gathers memes #04

The man who gathers memes in this opportunity brings him a harvest for the month of July, is delicate and strong, with a characteristic sarcastic touch, to satisfy our demanding palate. Just start and I hope you enjoy it ...

 

 

 

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BANNERGnulinuxrocks

 

What is a multi-user Operating system ? When the OS allows multiple people to use the computer at the same time without affecting other's stuff, it becomes a multi-user OS. Like wise Linux is also belongs to above mentioned category. There can be having multiple users, groups with their own personal files and preferences. So, this article will be helpful for you in below actions.

 

  • Managing Users ( Create/Edit/Delete accounts, Suspend accounts )
  • Manage User's Passwords ( Set Password policies, Expiration, further modifications )
  • Manage Groups ( Create/Delete user groups )

 

From this article we will discuss mostly useful Linux commands with their syntax's.


How to create a user

 

1) useradd : Add a user

 

syntax : useradd 

eg : We will create a user named ""Jesica". The command is useradd jesica . First i switch to root user with sudo su command as i am a sudo user.

UGLINUX1.png

You can see when we created the user in root account, it just added the user without asking the password for the newly created user. So now we will create a password for the user jesica.

 

 

2) passwd : set a password for users

 

syntax : passwd 

UGLINUX2.png

Here, i set a password for jesica. I set the password also as "jesica".You can use your own. The password you are writing will not be displayed for security reasons. As my password only having 6 characters, we get a message saying password is shorter than 8 characters. Those are password policies. We will discuss later in this article.

 

* Now we have created a new user with command useradd and set a password with passwd command. This is done in CentOS. But in some other linux distributions, adduser command will be used instead of useradd.

 * If you are a normal user, you have to be a super user to add a new user. So you have to use the commands as sudo useradd and sudo passwd .

 

Where all of these users are residing ?

We discussed these stuff in "Linux File System Hierarchy" article. As /root directory is root user's home directory, normal user's home directory is /home. Inside of /home directory all the user's profiles are stored. You can use the command ls /home to check who are currently in your OS. Check the below image, which shows my users in my OS.

 UGLINUX3.png

 

 

What is /etc/passwd file ?

 

When you created a user with command useradd without any options, there are some configuration file which are changing. Those are as below

 

  1. /etc/passwd
  2. /etc/shadow
  3. /etc/groups
  4. /etc/gshadow

 

Output of the above files are as below according to my OS.

 

1. /etc/passwd file

UGLINUX4.png

 

 

2. /etc/shadow file

UGLINUX5.png 

 

3. /etc/group file

UGLINUX6.png

 

When we created a new user with useradd command without any options, /etc/passwd file sets reasonable defaults for all field in that file for the new user. It is just a text file which contains useful information about the users like username, user id, group id, user's home directory path, shell and etc.

 

If we discuss about the fields in /etc/passwd file, eg : student:x:1000:1000:student:/home/student:/bin/bash

 

1. student : This is the username. To login we use this name.

 

2. x : This is the password. This is an encrypted password stored in /etc/shadow file. You can see the password record in /etc/shadow file for user student in the above image.

 

3. 1000 : This is the user id. Each an every user should have UID. This is zero for root user and 1-99 is for predefined user accounts and 100-999 is for system administrative accounts. Normal users are having User IDs starting from 1000. Extra - Also you can use command id for viewing user details.

 

4. 1000 : Primary group ID ( GID ). see /etc/group file on left side.

5. student : Comment field

6. /home/student : User's home directory

7. /bin/bash : The shell used by the user

 

 

* Summary of the above

 

  • When a user created, new profile will be created in /home/username by default
  • Hidden files like .bashrc , .bash_profile , .bash_logout will be copied to user's home directory. Environmental variables for the user is set by those hidden files and they will be covered in future articles.
  • A separate groups will be created for each user with their name.

 

Useradd command with some options

 

1.) If accidentally user's home directory is not created with useradd command.

 UGLINUX7.png

 

If you want to create a user without the home directory, useradd -M panda.

 

2.) If you want to move your home directory to a separate directory

UGLINUX8.png 

 

In the above command you have to use useradd command and then -d option for changing the default home directory path and /boo is the new home directory. Last put the username. You can see the below image. /etc/passwd file has a different home directory entry for user boo, Because we changed it's home directory.

UGLINUX9.png 

 

3.) Add a comment for the user when adding

UGLINUX10.png 

 

In /etc/passwd file :

UGLINUX11.png 

 

 

4.) Create a user by your own UID, useradd -u

5.) Create a user by your own UID and GID, useradd -u -g

6.) Create a user adding to a different groups, useradd -G There groups can be one or more and should be separated with a comma (,) the groups.

7.) To create a user, but disable shell login useradd -s /sbin/nologin With the above command, we can disable shell interaction with the user. But the account is active.


 

How to remove an account

 

3. userdel : Remove a user

 

syntax : userdel

 

eg : userdel -r

 

* When deleting the user, go with option -r. Why is it ? With -r option, it removes user with it's home directory. If removed without -r option, user's home directory will not be deleted.


 

How to modify an user account

 

4. usermod : Modify a user

 

syntax : usermod

 

* Here we can use all the options used in useradd command. Below are some options which is not discussed above.


 

1.) How to change the user's name

 

usermod -l

 

2.) To lock a user

 

usermod -L

 

3.) To unlock a user

 

usermod -U

 

4.) To change the group of a user

 

usermod -G

 

5.) To append a group to a user

 

usermod -aG

 

* Here appending means adding groups without removing the already existing groups. But if we use without -a, it removes the existing groups and join to new groups. This is relevant under primary groups and supplementary groups.

 

What is a group ?

 

Group is a collection of one or more users in Linux OS. Same as users, groups also have a group name and a id ( GID ). The group details can be found in /etc/group file. There are two types of main groups in Linux OS. Those are Primary groups and Supplementary groups. Every user once created is getting a new groups with the user's account name. That is the primary group and Supplementary groups are groups having one or more users inside.


 

How to create a group

 

4. groupadd : create a linux group

 

syntax : groupadd

 

Few examples

 

1.) To create a group named "student"

 

groupadd student

 

2.) Define a different group id ( GID )

 

groupadd -g 5000 student


 

How to modify an existing group

 

5. groupmod : modify a group

 

syntax : groupmod <options> <group name>

 

To change the name of the group, groupmod -n To change the group if, groupmod -g

 


 

How to delete an existing group

 

6. groupdel : delete a group

 

syntax : groupdel <group name>


 

How to manage user passwords using password policy ?

 

As we discussed above, while /etc/passwd file stores user details, /etc/shadow file stores user's password details. I attached an image of /etc/shadow file in the above. Here we use a term named Password aging. From that we use command chage edit the password aging policy. Look at the below image.

 UGLINUX12.png

Refer the above image and the options are as below.

 

  • chage -d 0 : Forcefully request the user to change the password in the next login.
  • chage -E Year-Month-Date : To expire an user account ( It should be in format YYYY-MM-DD ) 
  • chage -M 90 : Set password policy for requesting password should be renewed in every 90 days
  • chage -m 7 : Minimum days should be 7 to wait for changing the password again.

 

* Inactive days are set to define from how many days the account will be kept inactive after password expiration. If the user didn't change the password within inactive period, the account will be expired. 

 

chage -l : To display user's current settings for password policy.

 

The default values for all of the above values ( password expiration days, inactive days and etc ) will be in the configuration file, /etc/login.defs text file. Including User account ID , Group Account ID configurations also can be seen there. You can change the values in the /etc/login.defs file as your requirement.

UGLINUX13.png 

 

Now you have learned mostly needed stuff in Linux Users and Groups. This is not a small topic. There are a lots of commands you need to refer under this topic.

 

 You can see our previous posts with related topics

 

 

 

 

 

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