news – Page 38 – Sick Gaming

Posted on December 18, 2019 by — Leave a comment

Make sysadmin work on Fedora easier with screen

When you manage a Linux instance, you’ll find that your job is made much easier by the many tools designed specifically to deal with something specific within the system. For example, if you need to install packages, you have easy-to-use package managers that make that a breeze. If you need to create, resize or delete filesystems, you can do so using tools that are built to be used by humans. The same goes for managing services and browsing logs with systemd using the systemctl and journalctl commands respectively. The screen tool is another such example.

You can run all of those tools directly at the command line interface. But if you’re connecting to a server remotely using SSH, sometimes you need another layer between you and the operating system so the command you’re running doesn’t stop if your remote connection terminates. Sysadmins do this to prevent sudden termination in case of a connection issue, but also on purpose to run a command that needs to keep running indefinitely in the background. Enter the screen utility.

Introducing screen

The screen tool allows you to have multiple sessions (called screens) that are independent from each other and that you can name, leave and join as you desire. It’s multi-tasking for the remote CLI. You can get started with it simply by running this command:

$ screen

The command creates a screen and connect you to it: your current session is now a screen. You can run any command that does something and doesn’t automatically terminate after a few seconds. For example, you might call a web app executable or a game server. Then press Ctrl+A and, right after that, the D key and you will detach from the screen, leaving it running in the background.

The Ctrl+A combination, given that it is part of every screen command, is often shortened in documentation to C-a. Then the detach command used earlier can be described simply as C-a d.

Getting in and out of sessions

If you want to connect to that screen again, run screen -r and you will attach to that screen. Just running screen will create a new screen, and subsequent screen -r commands will print out something like this:

There are several suitable screens on: 5589.pts-0.hostname (Detached) 5536.pts-0.hostname (Detached) Type "screen [-d] -r [pid.]tty.host" to resume one of them.

You can then choose whether to resume the first or the second screen you created by running either one of these commands:

$ screen -r 5536
$ screen -r 5589

Adding the rest of the name of the string is optional in this case.

Named screens

If you know you’ll have multiple screens, you might want to be able to connect to a screen using a name you choose. This is easier than choosing from a list of numbers that only reflect the process IDs of the screen sessions. To do that, use the -S option as in the following example:

$ screen -S mywebapp

Then you can resume that screen in the future using this command:

$ screen -r mywebapp

Starting a process in the background using screen

An optional argument is the command to be executed inside the created session. For example:

$ screen -S session_name command args

This would be the same as running:

$ screen -S session_name

…And then running this command inside the screen session:

$ command args

The screen session will terminate when the command finishes its execution.

This is made particularly useful by passing the -dm option, which starts the screen in the background without attaching to it. For example, you can copy a very large file in the background by running this command:

$ screen -S copy -d -m cp /path/to/file /path/to/output

Other screen features

Now that you’ve seen the basics, let’s see some of the other most commonly used screen features.

Easily switching between windows in a screen

When inside a screen, you can create a new window using C-a c. After you do that, you can switch between the windows using C-a n to go to the next one and C-a p to go to the previous window. You can destroy (kill) the current window with C-a k.

Copying and pasting text

The screen tool also enables you to copy any text on the screen and paste it later wherever you can type some text.

The C-a [ keybinding frees your cursor of any constraints and lets it go anywhere your will takes it using the arrow keys on your keyboard. To select and copy text, move to the start of the string you want to copy, and press Enter on the keyboard. Then move the cursor to the end of the text you want to copy and press Enter again.

After you’ve done that, use C-a ] to paste that text in your shell. Or you can open a text editor like vim or nano and paste the text you copied there.

Important notes about screen

Here are some other tips to keep in mind when using this utility.

Privileged sessions vs. sudo inside a screen

What if you need to run a command with root privileges inside screen? You can run either of these commands:

$ screen -S sessionname sudo command
$ sudo screen -S sessionname command

Notice that the second command is like running this command:

# screen -S sessionname command

Seeing things this way makes it a lot more obvious coupled with the fact that each screen is associated to a user:

The first one creates a screen with root privileges that can be accessed by the current user even if, within that screen, they switch to another user or root using the sudo -i command.
The second one creates a screen that can only be accessed by the root user, or by running sudo screen -r as a user with the appropriate sudo access.

Notes about screen in systemd units

You might be tempted to run a screen session in the background as part of a systemd unit executed at startup, just like any Unix daemon. That way you can resume the screen session and interact with whatever you ran that way. That can work, but you need to consider that it requires the right setup.

By default, systemd assumes services are either oneshot, meaning they set up something and then shut down, or simple. A service is simple by default when you create a unit file with no Type. What you actually need to do is to set the Type to forking, which describes screen‘s actual behavior when the -dm option is passed. It starts the process and then forks itself, leaving the process running in the background while the foreground process closes.

If you don’t set that, that screen behavior is interpreted by systemd as the service exiting or failing. This causes systemd to kill the background process when the foreground process exits, which is not what you want.

Photo by Vlad Tchompalov on Unsplash.

Posted on December 16, 2019 by — Leave a comment

Setting up the sway window manager on Fedora

Sometimes during a critical activity, working with overlapping windows becomes counterproductive. You might find a tiled window manager like sway to be a good alternative.

Sway is a tiling Wayland compositor. It has the advantage of compatibility with an existing i3 configuration, so you can use it to replace i3 and use Wayland as the display protocol.

Installing sway

To setup sway, open a new terminal and type the following command

sudo dnf install sway

Once the installation is completed, log out of your user session. At the login screen, select your user account. Before you enter your password, choose Sway from the menu, as shown in the following image.

After login, your desktop looks like this:

Configuration

To begin configuration, copy the default config into your user directory. Do that using the following commands.

mkdir -p .config/sway
cp /etc/sway/config ~/.config/sway/

Sway is highly configurable. It’s suggested you read the project’s wiki page to fine tune your settings. For example, to change the keyboard layout, open a new terminal and run this command:

$ swaymsg -t get_inputs
[george@mrwhite ~]$ swaymsg -t get_inputs Input device: VirtualPS/2 VMware VMMouse Type: Mouse Identifier: 2:19:VirtualPS/2_VMware_VMMouse Product ID: 19 Vendor ID: 2 Libinput Send Events: enabled Input device: VirtualPS/2 VMware VMMouse Type: Mouse Identifier: 2:19:VirtualPS/2_VMware_VMMouse Product ID: 19 Vendor ID: 2 Libinput Send Events: enabled Input device: AT Translated Set 2 keyboard Type: Keyboard Identifier: 1:1:AT_Translated_Set_2_keyboard Product ID: 1 Vendor ID: 1 Active Keyboard Layout: Portuguese (Brazil) Libinput Send Events: enabled

Copy the identifier keyboard code. Open your ~/.config/sway/config file with your text editor and edit the configuration accordingly:

## Input configuration
input "1:1:AT_Translated_Set_2_keyboard" { xkb_layout br
}

Save the settings. To reload the configurations, press Super+Shift+c. (Typically the Super key is mapped to the logo key on a PC.)

Waybar

Sway’s default status bar may not have all the functions you want. Fortunately Waybar is a good replacement. To install, run the follow commands. (Note, however, that COPR is not an official Fedora repository and not supported by the Fedora Project.)

sudo dnf copr enable alebastr/waybar sudo dnf install waybar

Open your ~/.config/sway/config file. Edit the bar configuration like this:

bar { swaybar_command waybar
}

Reload the configuration and you’ll now see the waybar in action, as shown below.

To customize the waybar, you can visit this wiki page for more details and ideas.

Alacritty

Alacritty is a terminal emulator that uses the GPU for rendering, and a good replacement for urxvt. To install run the following lines

sudo dnf copr enable pschyska/alacritty
sudo dnf install alacritty

To enable it as default terminal emulator edit your ~/.config/sway/config. Change this line:

set $term urxvt256c-ml

To:

set $term alacritty

Reload your configuration.

When you open a new terminal with Super+C, alacritty will be open as seen in the following image:

Photo by Ivan Vranić on Unsplash.

Posted on December 13, 2019 by — Leave a comment

Organizing those 1s and 0s

“It’s all 1s and 0s.” People say this when they’re making a joke or a sarcastic remark. When it comes to computers thought, it’s really true. And at the hardware level, that’s all there is. The processor, the memory, various forms of storage, USB, HDMI, and network connections, along with everything else in that cell-phone, tablet, laptop, or desktop only uses 1s and 0s. Bytes provide for the grouping of the 1s and 0s. So they are a big help in keeping them organized. Let’s looks at how they do that.

Bytes are the unit of measure for data and programs stored and used in your computer. Though the byte has existed for a long time in computer history and has taken several forms, it’s current 8 bit length is well settled. Taken either singly or as adjacent groups, bytes are the generally accepted most common way the Bits in a computer are kept organized.

So what’s a bit? A bit is a binary digit; that is it can have only two values. In computers the two values a bit can have are zero (0) and one (1). That’s it, no other choices. A byte is just eight binary bits that are taken together to represent binary numbers. Through various coding schemes the numbers can represent a wide variety of other things like the characters we write with.

The table below shows a single Little-Endian byte showing individual bits of this byte and their associated powers of two. The decimal values of each power of two is show with each bit for reference. The line between Bit 3 and Bit 4 is where the byte is sub divided into four bit groups called Nibbles. Little-Endian is a very commonly used byte format. Stay tuned for more on Endians. If you’re curious about the name, do a search on (etymology of endian).

One Little-Endian Byte:

	Bit0	Bit1	Bit2	Bit3	Bit4	Bit5	Bit6	Bit7
Power of 2	2⁰	2¹	2²	2³	2⁴	2⁵	2⁶	2⁷
Decimal value	1	2	4	8	16	32	64	128

Each nibble of a byte can hold a four bit binary number as shown in the following table. If a bit is set to “1” that power of two adds to the value of the nibble. If a bit is set to “0” that power of two does not add to the value of the nibble. A byte which is two nibbles can hold a two digit hexadecimal number. Bits are really all that a computer can use. Programmers and engineers developing computer hardware use hexadecimal to make dealing with the bits easier. In the table below the least significant bit is on the left 2⁰, 2¹, 2², 2³

One Little-Endian Nibble:

Binary Number	Hexidecimal Value
0000	0
1000	1
0100	2
1100	3
0010	4
1010	5
0110	6
1110	7
0001	8
1001	9
0101	A
1101	B
0011	C
1011	D
0111	E
1111	F

I’ll explain Littel-Endian starting with a one byte diagram. The longer lines at the end of this frame are the boundaries of the byte so if you were drawing a group of adjacent bytes it would be clear where one byte left off and another began. The small lines divide the frame into individual locations where each of the eight bits can be shown. The medium line in the middle divides the byte into two equal four bit pieces which are the nibbles. Nibbles also have a long and varied history. I’ve never seen that they have been standardized. However the current well settled view is that nibbles are groups of four bits as I have shown them below. All of these lines only exist as people draw bytes. The lines don’t exist in the computer.

The Lower Nibble and Upper Nibble are labels as they would be used in a Little-Endian byte. In Little-Endian, the least significant digit is on the left end of a number. So the Lower Nibble is the least significant half of the number in the byte. Likewise the least significant bit is on the left LSBit (usually noted as LSB) stands for Least Significant Bit. and the most significant bit is on the right. The Upper Nibble on the right is the most significant half of the number. MSBit (usually noted as MSB) is the most significant bit. This is opposite to how we write decimal numbers with the most significant digit on the left. This is called Little-Endian because the “little end” of the number comes first.

With the byte being able to hold two hexadecimal digits, a byte can hold hexadecimal numbers between 00 and FF (0 to 255 in decimal) So if you are using bytes to represent the characters of a human readable language you just give each character, punctuation mark, etc. a number. (Then of course get everyone to agree with the coding you invented.) This is only one use for bytes. Bytes are also used as program code that your computer runs, numbers for various data you might have, and everything else that inhabits a computer in the CPU, memory, storage, or zooming around on the various buses and interface ports.

As it turns out there are two commonly used byte formats. Little-Endian has been used in the prior examples. Its feature is having the least significant digit on the left and the most significant digit on the right. If we were to write the decimal number 1620 in Little-Endian format it would be 0261.

There is also a byte format called Big-Endian. As you might expect it is opposite of Little-Endian with the most significant digit on the left and the least significant digit on the right. Like we write decimal numbers.

There are reasons for using both and the meaty reasons are beyond the scope of this article. However, Little-Endian tends to be used in microprocessors. The x86-64 processors in most PCs use the Little-Endian byte format. Though the later generations do have special instructions that provide limited use of Big-Endian format. The Big-Endian byte format is widely used in networking and notably in those big Z computers. Now you’re not necessarily limited to one or the other. The newer ARM processors can use either Endian format. Devices like microprocessors that can use both Big-Endian and Little Endian are sometimes referred to as Bi-Endian.

Well, sometimes you really need more than one byte to hold a number. To that end there are longer formats available that are composed of multiple bytes. For instance: The x86-64 processors Have Words which are 16 bits or 2 bytes that happen to be lined up next to each other head to tail, so to speak. They also have Double Words (32 bits or 4 bytes), and Quad Words (64 bits or 8 bytes). Now these are just examples of data forms made available by the processor hardware.

Programmers working with languages have many more ways to organize the bits and bytes. When the program is ready, a compiler or another mechanism converts the way that the program has bits and bytes organized into data forms that the CPU hardware can deal with.

Posted on December 11, 2019 by — Leave a comment

How to rebase to Fedora 31 on Silverblue

Silverblue is an operating system for your desktop built on Fedora. It’s excellent for daily use, development, and container-based workflows. It offers numerous advantages such as being able to roll back in case of any problems. If you want to update to Fedora 31 on your Silverblue system, this article tells you how. It not only shows you what to do, but also how to revert back if anything unforeseen happens.

Prior the the update to Fedora 31 it is better to do any pending upgrades.

Updating using GNOME Software

Unfortunately the update can’t be done in GNOME Software right now, because of a bug in GNOME Software itself. For additional information please look at upstream issue.

Updating using terminal

If you do not like GNOME Software or like to do everything in terminal, than this next guide is for you.

Updating to Fedora 31 using terminal is easy. First, check if the 31 branch is available, which should be true now:

$ ostree remote refs fedora

You should see the following in the output:

fedora:fedora/31/x86_64/silverblue

Next, rebase your system to the Fedora 31 branch.

$ rpm-ostree rebase fedora:fedora/31/x86_64/silverblue

Finally, the last thing to do is restart your computer and boot to Fedora 31.

How to revert things back

If anything bad happens — for instance, if you can’t boot to Fedora 31 at all — it’s easy to go back. Just pick the previous entry in GRUB, and your system will start in its previous state before switching to Fedora 31. To make this change permanent, use the following command:

$ rpm-ostree rollback

That’s it. Now you know how to rebase to Fedora 31 and back. So why not do it today?

Posted on December 9, 2019 by — Leave a comment

Contribute at the Fedora Test Week for Kernel 5.4

The kernel team is working on final integration for kernel 5.4. This version was just recently released, and will arrive soon in Fedora. This version has many security fixes included. As a result, the Fedora kernel and QA teams have organized a test week from Monday, December 09, 2019 through Monday, December 16, 2019. Refer to the wiki page for links to the test images you’ll need to participate. Read below for details.

How does a test week work?

A test day/week is an event where anyone can help make sure changes in Fedora work well in an upcoming release. Fedora community members often participate, and the public is welcome at these events. If you’ve never contributed before, this is a perfect way to get started.

To contribute, you only need to be able to do the following things:

Download test materials, which include some large files
Read and follow directions step by step

The wiki page for the kernel test day has a lot of good information on what and how to test. After you’ve done some testing, you can log your results in the test day web application. If you’re available on or around the day of the event, please do some testing and report your results.

Happy testing, and we hope to see you in the Test Week.

Posted on December 6, 2019 by — Leave a comment

5 cool terminal pagers in Fedora

Large files like logs or source code can run into the thousands of lines. That makes navigating them difficult, particularly from the terminal. Additionally, most terminal emulators have a scrollback buffer of only a few hundred lines. That can make it impossible to browse large files in the terminal using utilities which print to standard output like cat, head and tail. In the early days of computing, programmers solved these problems by developing utilities for displaying text in the form of virtual “pages” — utilities imaginatively described as pagers.

Pagers offer a number of features which make text file navigation much simpler, including scrolling, search functions, and the ability to feature as part of a pipeline of commands. In contrast to most text editors, some terminal pagers do not require loading the entire file for viewing, which makes them faster, especially for very large files.

In the modern era of Linux computing, terminal emulators are more sophisticated than ever. They offer support for a kaleidoscope of colors, terminal resizing, as well as a host of other features to make parsing text on screen easier and more efficient. Terminal pagers have undergone a similar evolution, from extremely simple UNIX utilities like pg and more, to sophisticated programs with a wide range of features, covering any number of use cases. With this in mind, we’ve put together a list of some of the most popular terminal paging utilities — more or less.

more is one of the earliest pagers, initially featured in version 3.0 BSD. The first implementation of more was written in 1978 by Daniel Halbert. Since then, more has become a ubiquitous feature of many operating systems, including Windows, OS/2, MacOS and most linux distributions.

more is a very lightweight utility. The version featured in util-linux runs to just under 2100 lines of C. However, this small footprint comes at a price. Most versions of more feature relatively limited functionality, with no support for backwards scroll or search. Commands are similarly stripped back: press enter to scroll one line, or space to scroll one page. Some other useful commands include:

Press v while reading to open the current file in your default terminal editor.
‘/pattern‘ let’s you search for the next occurrence of pattern.
:n and :p will open the next and previous files respectively when more is called with more than one file as arguments

Less

less was initially conceived as a successor to more, addressing some of its limitations. Building on the functionality of more, less adds a number of useful features including backwards scroll, backwards search. It is also more amenable to window resizing.

Navigation in less is similar to more, though less borrows a few useful commands from the vi editor as well. Users can navigate the document using the familiar home row navigational keys. A glance at the man page for less reveals a fairly rich repertoire of available commands. Some particularly useful examples include:

?pattern lets you search backwards in the file for pattern
&pattern shows only lines which feature pattern. This is particularly useful for those who find themselves issuing $ grep pattern | less regularly.
Calling less with the -s (–sqeueeze-blank-lines) flag allows you to view text files with large gaps. Multiple newline characters are reduced to single breaks.
s filename, called from within the program, saves input to filename (if input is a pipe).
Alternatively, calling less with the -o filename flag will save the input of less to filename.

With this enhanced functionality comes a little extra weight. The version of less that ships with Fedora at the time of writing clocks in at around 25000 lines of source code. Granted, for all but the most storage constrained systems, this is a non-issue. Besides, less is more than more.

Most

While less aims to expand on the existing capabilities of more, most takes a different approach. Rather than expanding on the traditional single file view, most gives users the ability to split their view into “windows.” Each window contains different files in different viewing modes.
Significantly, most takes into account the width of its input text. The default viewing mode doesn’t wrap text (-S in less), a feature particularly useful when dealing with “wide” files. While these design decisions might represent a significant departure from tradition for some users, the end result is very powerful.

In addition to the navigation commands offered by more, most uses intuitive mnemonics for file navigation. For example, t moves to the top of a file, and b moves to the bottom. As a result, users unfamiliar with vi and its descendants will find most to be refreshingly simple.

The distinguishing feature of most is its ability to split windows and contexts quickly and easily. For example, one could open two distinct text files using the following:

$ most textFile1.txt textFile2.txt

In order to split the screen horizontally, use the key combos Ctrl+x, 2 or Ctrl+w, 2. The command :n will open the next file argument in a given window, offering a split screen view of two files:

If you turn wrap off in one window, it does not affect the behavior of other windows. The \ character indicates a wrap or fold, while the $ character indicates that the file extends past the limitations of the current window.

pspg

Those who work with SQL databases often need to be able to examine the contents of our databases at a glance. The command line interfaces for many popular open source DBMS’s, such as MySQL and PostGreSQL, use the system default pager to view outputs that don’t fit on a single screen. Utilities like more and less are designed around the idea of presenting text files, but for more structured data, leave something to be desired. Naive text paginating programs have no concept of broad, tabular data, which can be frustrating when dealing with large queries.

pspg attempts to address this by offering users the ability to freeze columns while viewing, sort data in situ, and colourize output. While pspg was intended initially to serve as a pager replacement for psql specifically, the program also supports the viewing of CSV data, and is a suitable drop-in replacement for mysql and pgcli.

Vim

In a modern, technicolor terminal, the idea of endless pages of drab grey on black text can feel like something of an anachronism. The syntax highlighting options offered by powerful text editors like vim can be useful for browsing source code. Furthermore, the search functions offered by vim vastly outclass the competition. With this in mind, vim ships with a shell script less.sh that lets vim serve as a replacement for conventional pagers.

To set vim as the default pager for man pages, add the following to your shell’s config (such as ~/.bashrc if using the default bash shell):

export MANPAGER="/bin/sh -c \"col -b | vim -c 'set ft=man ts=8 nomod nolist nonu noma' -\""

Alternatively, to set vim as the default pager system-wide, locate the less.sh script. (You can find it at /usr/share/vim/vim81/macros/ on current Fedora systems.) Export this location as the variable PAGER to set it as default, or under an alias to invoke it explicitly.

Photo by Cathy Mü on Unsplash.

Posted on December 4, 2019 by — Leave a comment

Fedora Desktops – Memory Footprints

There are over 40 desktops in Fedora. Each desktop has it’s own strengths and weaknesses. Usually picking a desktop is a very personal preference based on features, looks, and other qualities. Sometimes, what you pick for a desktop is limited by hardware constraints.

This article is to help people compare Fedora desktops based on the desktop baseline memory. To narrow the scope, we are only looking at the desktops that have an official Fedora Live image.

Installation and Setup

Each of the desktops was installed on it’s own KVM virtual machine. Each virtual machine had 1 CPU, 4GB of memory, 15 GB virtio solid state disk, and everything else that comes standard on RHEL 8.0 kvm.

The images for installation were the standard Fedora 31 Live images. For GNOME, that image was the Fedora Workstation. For the other desktops, the corresponding Spin was used. Sugar On A Stick (SOAS) was not tested because it does not install easily onto a local drive.

The virtual machine booted into the Live CD. “Install to Hard Disk” was selected. During the install, only the defaults were used. A root user, and a regular users were created. After installation and reboot, the Live image was verified to not be in the virtual CDROM.

The settings for each desktop was not touched. They each ran whatever settings came default from the Live CD installation. Each desktop was logged into via the regular user. A terminal was opened. Using sudo each machine ran “dnf -y update”. After update, in that sudo terminal, each machine ran “/sbin/shutdown -h now” to shut down.

Testing

Each machine was started up. The desktop was logged into via the regular user. Three of the desktop terminals were opened. xterm was never used, it was always the terminal for that desktop, such as konsole.

In one terminal, top was started and M pressed, showing the processes sorted by memory. In another terminal, a simple while loop showed “free -m” every 30 seconds. The third terminal was idle.

I then waited 5 minutes. This allowed any startup services to finish. I recorded the final free result, as well as the final top three memory consumers from top.

Results

Cinnamon
- 624 MB Memory used
- cinnamon 4.8% / Xorg 2.2% / dnfdragora 1.8%
GNOME
- 612 MB Memory used
- gnome-shell 6.9% / gnome-software 1.8% / ibus-x11 1.5%
KDE
- 733 MB Memory used
- plasmashell 6.2% / kwin_x11 3.6% / akonadi_mailfil 2.9%
LXDE
- 318 MB Memory used
- Xorg 1.9% / nm-applet 1.8% / dnfdragora 1.8%
LXQt
- 391 MB Memory used
- lxqt-panel 2.2% / pcmanfm-qt 2.1% / Xorg 2.1%
MATE
- 465 MB Memory used
- Xorg 2.5% / dnfdragora 1.8% / caja 1.5%
XFCE
- 448 MB Memory used
- Xorg 2.3% / xfwm4 2.0% / dnfdragora 1.8%

Conclusion

I will let the numbers speak for themselves.

Remember that these numbers are from a default Live install. If you remove, or add services and features, your memory usage will change. But this is a good baseline to look at if you are determining your desktop based on memory consumption.

Posted on December 3, 2019 by — Leave a comment

Using Ansible to organize your SSH keys in AWS

If you’ve worked with instances in Amazon Web Services (AWS) for a long time, you may run into this common issue. It’s not technical, but more to do with the human nature of getting too comfortable. When you launch a new instance in a region you haven’t used recently, you may end up creating a new SSH key pair. This leads to having too many keys, which can become complicated and disordered.

This article shows you a way to have your public key in all regions. A recent Fedora Magazine article includes one solution. But the solution in this article is automated even further, and in a more concise and scalable way.

Say you have a Fedora 30 or 31 desktop system where your key is stored, and Ansible is installed as well. These two things together provide the solution to this problem and many more.

With Ansible’s ec2_key module, you can create a simple playbook that will maintain your SSH key pair in all regions. If you need to add or remove keys, it’s as simple as adding and removing lines from a file.

Setting up and running the playbook

To use the playbook, first install necessary dependencies for the ec2_key module:

$ sudo dnf install python3-boto python3-boto3

The playbook is simple: you need only to change your key and its name as in the example below. After that, run the playbook and it iterates over all the public AWS regions listed. The example also includes the restricted regions in case you have access. To include them, uncomment each line as needed, save the file, and then run the playbook again.

---
- name: Maintain an ssh key pair in ec2 hosts: localhost connection: local gather_facts: no vars: ansible_python_interpreter: python tasks: - name: Make available your ssh public key in ec2 for new instances ec2_key: name: "YOUR KEY NAME GOES HERE" key_material: 'YOUR KEY GOES HERE' state: present region: "{{ item }}" with_items: - us-east-2 #US East (Ohio) - us-east-1 #US East (N. Virginia) - us-west-1 #US West (N. California) - us-west-2 #US West (Oregon) - ap-east-1 #Asia Pacific (Hong Kong) - ap-south-1 #Asia Pacific (Mumbai) - ap-northeast-2 #Asia Pacific (Seoul) - ap-southeast-1 #Asia Pacific (Singapore) - ap-southeast-2 #Asia Pacific (Sydney) - ap-northeast-1 #Asia Pacific (Tokyo) - ca-central-1 #Canada (Central) - eu-central-1 #EU (Frankfurt) - eu-west-1 #EU (Ireland) - eu-west-2 #EU (London) - eu-west-3 #EU (Paris) - eu-north-1 #EU (Stockholm) - me-south-1 #Middle East (Bahrain) - sa-east-1 #South America (Sao Paulo) # - us-gov-east-1 #AWS GovCloud (US-East) # - us-gov-west-1 #AWS GovCloud (US-West) # - ap-northeast-3 #Asia Pacific (Osaka-Local) # - cn-north-1 #China (Beijing) # - cn-northwest-1 #China (Ningxia)

This playbook requires AWS access via API, as well. To do this, use environment variables as follows:

$ AWS_ACCESS_KEY="aws-access-key-id" AWS_SECRET_KEY="aws-secret-key-id" ansible-playbook ec2-playbook.yml

Another option is to install the aws cli tools and add the credentials as explained in a previous Fedora Magazine article. It is not recommended to insert these values in the playbook if you store it anywhere online! You can find this playbook code on GitHub.

After the playbook finishes, confirm that your key is available on the AWS console. To do that:

Log into your AWS console
Go to EC2 > Key Pairs
You should see your key listed. The only limitation is that you have to check region-by-region with this method.

Another way is to use a quick command in a shell to do this check for you.

First create a variable with all regions on the playbook:

AWS_REGION="us-east-1 us-west-1 us-west-2 ap-east-1 ap-south-1 ap-northeast-2 ap-southeast-1 ap-southeast-2 ap-northeast-1 ca-central-1 eu-central-1 eu-west-1 eu-west-2 eu-west-3 eu-north-1 me-south-1 sa-east-1"

Then do a for loop and you will get the result from aws API:

for each in ${AWS_REGION} ; do aws ec2 describe-key-pairs --key-name <YOUR KEY GOES HERE> ; done

Keep in mind that to do the above you need to have the aws cli installed.

Posted on November 29, 2019 by — Leave a comment

A quick introduction to Toolbox on Fedora

Toolbox allows you to sort and manage your development environments in containers without requiring root privileges or manually attaching volumes. It creates a container where you can install your own CLI tools, without installing them on the base system itself. You can also utilize it when you do not have root access or cannot install programs directly. This article gives you an introduction to toolbox and what it does.

Installing Toolbox

Silverblue includes Toolbox by default. For the Workstation and Server editions, you can grab it from the default repositories using dnf install toolbox.

Creating Toolboxes

Open your terminal and run toolbox enter. The utility will automatically request permission to download the latest image, create your first container, and place your shell inside this container.

$ toolbox enter
No toolbox containers found. Create now? [y/N] y
Image required to create toolbox container.
Download registry.fedoraproject.org/f30/fedora-toolbox:30 (500MB)? [y/N]: y

Currently there is no difference between the toolbox and your base system. Your filesystems and packages appear unchanged. Here is an example using a repository that contains documentation source for a resume under a ~/src/resume folder. The resume is built using the pandoc tool.

$ pwd /home/rwaltr $ cd src/resume/ $ head -n 5 Makefile all: pdf html rtf text docx pdf: init pandoc -s -o BUILDS/resume.pdf markdown/* $ make pdf
bash: make: command not found
$ pandoc -v
bash: pandoc: command not found

This toolbox does not have the programs required to build the resume. You can remedy this by installing the tools with dnf. You will not be prompted for the root password, because you are running in a container.

$ sudo dnf groupinstall "Authoring and Publishing" -y && sudo dnf install pandoc make -y
... $ make all #Successful builds
mkdir -p BUILDS
pandoc -s -o BUILDS/resume.pdf markdown/*
pandoc -s -o BUILDS/resume.html markdown/*
pandoc -s -o BUILDS/resume.rtf markdown/*
pandoc -s -o BUILDS/resume.txt markdown/*
pandoc -s -o BUILDS/resume.docx markdown/*
$ ls BUILDS/
resume.docx resume.html resume.pdf resume.rtf resume.txt

Run exit at any time to exit the toolbox.

$ cd BUILDS/
$ pandoc --version || ls
pandoc 2.2.1
Compiled with pandoc-types 1.17.5.4, texmath 0.11.1.2, skylighting 0.7.5
...
for a particular purpose.
resume.docx resume.html resume.pdf resume.rtf resume.txt
$ exit logout
$ pandoc --version || ls
bash: pandoc: command not found...
resume.docx resume.html resume.pdf resume.rtf resume.txt

You retain the files created by your toolbox in your home directory. None of the programs installed in your toolbox will be available outside of it.

Tips and tricks

This introduction to toolbox only scratches the surface. Here are some additional tips, but you can also check out the official documentation.

Toolbox –help will show you the man page for Toolbox
You can have multiple toolboxes at once. Use toolbox create -c Toolboxname and toolbox enter -c Toolboxname
Toolbox uses Podman to do the heavy lifting. Use toolbox list to find the IDs of the containers Toolbox creates. Podman can use these IDs to perform actions such as rm and stop. (You can also read more about Podman in this Magazine article.)

Photo courtesy of Florian Richter from Flickr.

Posted on November 27, 2019 by — Leave a comment

Create virtual machines with Cockpit in Fedora

This article shows you how to install the software you need to use Cockpit to create and manage virtual machines on Fedora 31. Cockpit is an interactive admin interface that lets you access and manage systems from any supported web browser. With virt-manager being deprecated users are encouraged to use Cockpit instead, which is meant to replace it.

Cockpit is an actively developed project, with many plugins available that extend how it works. For example, one such plugin is “Machines,” which interacts with libvirtd and lets users create and manage virtual machines.

Installing software

The required software prerequisites are libvirt, cockpit and cockpit-machines. To install them on Fedora 31, run the following command from a terminal using sudo:

$ sudo dnf install libvirt cockpit cockpit-machines

Cockpit is also included as part of the “Headless Management” package group. This group is useful for a Fedora based server that you only access through a network. In that case, to install it, use this command:

$ sudo dnf groupinstall "Headless Management"

Setting up Cockpit services

After installing the necessary packages it’s time to enable the services. The libvirtd service runs the virtual machines, while Cockpit has a socket activated service to let you access the Web GUI:

$ sudo systemctl enable libvirtd --now
$ sudo systemctl enable cockpit.socket --now

This should be enough to run virtual machines and manage them through Cockpit. Optionally, if you want to access and manage your machine from another device on your network, you need to expose the service to the network. To do this, add a new rule in your firewall configuration:

$ sudo firewall-cmd --zone=public --add-service=cockpit --permanent
$ sudo firewall-cmd --reload

To confirm the services are running and no issues occurred, check the status of the services:

$ sudo systemctl status libvirtd
$ sudo systemctl status cockpit.socket

At this point everything should be working. The Cockpit web GUI should be available at https://localhost:9090 or https://127.0.0.1:9090. Or, enter the local network IP in a web browser on any other device connected to the same network. (Without SSL certificates setup, you may need to allow a connection from your browser.)

Creating and installing a machine

Log into the interface using the user name and password for that system. You can also choose whether to allow your password to be used for administrative tasks in this session.

Select Virtual Machines and then select Create VM to build a new box. The console gives you several options:

Download an OS using Cockpit’s built in library
Use install media already downloaded on the system you’re managing
Point to a URL for an OS installation tree
Boot media over the network via the PXE protocol

Enter all the necessary parameters. Then select Create to power up the new virtual machine.

At this point, a graphical console appears. Most modern web browsers let you use your keyboard and mouse to interact with the VM console. Now you can complete your installation and use your new VM, just as you would via virt-manager in the past.

Photo by Miguel Teixeira on Flickr (CC BY-SA 2.0).