Sometimes, I find it really time-consuming when I wanted to learn a practical example of a given Unix command using man pages. So, I started to look for some good alternatives to man pages which are focused on mostly examples, skipping all other comprehensive text parts. Thankfully, there are some really good alternatives out there. In this tutorial, we will be discussing some alternatives to man pages for Unix-like operating systems.

The “electrosensitive” are moving to a cellphone-free town. But is their disease real?

You can turn your phone on in Green Bank, W.Va., but you won’t get a trace of a signal. If you hit scan on your car’s radio, it’ll cycle through the dial endlessly, never pausing on a station. This remote mountainous town is inside the U.S. National Radio Quiet Zone, a 13,000–square-mile area where most types of electromagnetic radiation on the radio spectrum (which includes radio and TV broadcasts, Wi-Fi networks, cell signals, Bluetooth, and the signals used by virtually every other wireless device) are banned to minimize disturbance around the National Radio Astronomy Observatory, home to the world’s largest steerable radio telescope. //

As The New Yorker recently pointed out in a blog post, EHS, along with these types of episodes, hint at the bizarre power of the nocebo effect: the flip-side of the placebo effect, in which inert substances or the suggestion of harm brings about real physical symptoms. In many studies of the nocebo effect, simply explaining to patients that a pill might trigger side effects has been enough to cause everything from back pain to erectile dysfunction. “If you believe that a substance, compound, or phenomena harms you, and you start experiencing symptoms, there’s confirmation for your belief right there, and then it’s a self-fulfilling prophecy,” Brian Dunning, a prominent skeptic who hosts the Skeptoid podcast and frequently takes on pseudoscientific claims, told me. “You see that your phone has a signal or that there’s a Wi-Fi router in the room, it further increases your stress level, and you have very real and very distressing physical symptoms. Once you have this confirming experience, it becomes really difficult to sit there and be told otherwise.”

Our brains’ expectations, it turns out, have a surprisingly potent effect on the functioning of our bodies. If the people who moved to Green Bank truly suffer from piercing headaches, nausea, and dizziness when they are around wireless signals, the nocebo effect (and previous instances of mass psychogenic diseases) is as good an explanation of anything we have so far.

Enjoy the security and benefits of a dedicated mailbox server in a highly available mail infrastructure.

The problems are well known when using free e-mail providers or shared hosting mail servers: My e-mail was sent but was it received on the other side? Why are my e-mails rejected by a blacklist? Are my e-mails secure when hundreds of other users are storing their mails on the same mailserver?

E-Mails are business critical and you should not be asking the questions above. The Private Mailbox Server offers a purely dedicated mailbox server in a highly available and redundant mail infrastructure. Your e-mails are stored securely on a private mailbox server; no other customers are using your mailbox server nor are able to access it. //

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100GB storage $86/mo, or 150/mo for high avail

Find files Based On their Permissions

The typical syntax to find files based on their permissions is:

$ find -perm mode

The MODE can be either with numeric or octal permission (like 777, 666.. etc) or symbolic permission (like u=x, a=r+x).

We can specify the MODE in three different ways as listed below.

• If we specify the mode without any prefixes, it will find files of exact permissions.
• If we use "-" prefix with mode, at least the files should have the given permission, not the exact permission.

• If we use "/" prefix, either the owner, the group, or other should have permission to the file. ///

  find . -not -perm -g=r

Before Microsoft and Intel dominated the PC market with a common platform, the CP/M operating system did something similar for small business machines in the late 1970s and early 1980s—until MS-DOS pulled the rug out from under it. Here’s more about CP/M, and why it lost out to MS-DOS.

Changing the group a user is associated to is a fairly easy task, but not everybody knows the commands, especially to add a user to a secondary group. We’ll walk through all the scenarios for you.

If you want to create a new group on your system, use the groupadd command following command, replacing new_group with the name of the group you want to create. You’ll need to use sudo with this command as well (or, on Linux distributions that don’t use sudo, you’ll need to run the su command on its own to gain elevated permissions before running the command).

sudo groupadd mynewgroup

To add an existing user account to a group on your system, use the usermod command, replacing examplegroup with the name of the group you want to add the user to andexampleusername with the name of the user you want to add.

usermod -a -G examplegroup exampleusername

For example, to add the user geek to the group sudo , use the following command:

usermod -a -G sudo geek

In the race against climate change, scientists at Harvard University propose that dimming sunlight could cool down the planet.

But what does that mean? The ambitious project involves launching a huge balloon into the stratosphere, carrying 600kg of calcium carbonate - or chalk, which would be sprayed 12 miles above the Earth’s surface.

Scientists will then monitor how the dust particles interact with the atmosphere. It’s a process known as solar geoengineering.

The chalk would, in theory, reflect sunlight and in turn slow global warming. Some experts predict the sky would also shift from blue to white during daylight hours.

Switching a mail provider is often combined with one major thought holding one back: What will happen to all my e-mails? I don't want to lose my e-mails!

Sure, if you used POP3 to download the e-mails to your mail client, the e-mails are not stored on the server anymore. This worked fine in the 90s and 00s but since mobile Internet there are usually multiple devices connected to your mailbox: Notebook, Workstation, Smartphone or even a Tablet. In such a scenario, only IMAP (IMAPv4 to be precise) can do the job: All the e-mails remain on the server (in the mailbox) but are synced to the local mail client. Every change in the local mail client is synced back to the server. Hence all the devices see the same status.

For a customer of Infiniroot we recently needed to find a way to migrate all the existing e-mails (more than 28'000) from a long-existing mailbox to a new mailbox located on the dedicated server of this customer. This is where we came across imapsync.

Public key authentication is a way of logging into an SSH/SFTP account using a cryptographic key rather than a password.

If you use very strong SSH/SFTP passwords, your accounts are already safe from brute force attacks. However, using public key authentication provides many benefits when working with multiple developers. For example, with SSH keys you can

• allow multiple developers to log in as the same system user without having to share a single password between them;
• revoke a single developer's access without revoking access by other developers; and
• make it easier for a single developer to log in to many accounts without needing to manage many different passwords. //

Method 1: Using ssh-copy-id

To copy your public key to your server, run the following command. Be sure to replace "x.x.x.x" with your server's IP address and SYSUSER with the name of the the system user your app belongs to.

ssh-copy-id SYSUSER@x.x.x.x

Method 2: Manual Configuration

If you don't have the ssh-copy-id command (for example, if you are using Windows), you can instead SSH in to your server and manually create the .ssh/authorized_keys file so it contains your public key.

First, run the following commands to make create the file with the correct permissions.

(umask 077 && test -d ~/.ssh || mkdir ~/.ssh)
(umask 077 && touch ~/.ssh/authorized_keys)

Next, edit the file .ssh/authorized_keys using your preferred editor. Copy and paste your id_rsa.pub file into the file. //

Correcting Permissions on the .ssh Directory

The instructions in this article will create your server's .ssh directory and .ssh/authorized_keys file with the correct permissions. However, if you've created them yourself and need to fix permissions, you can run the following commands on your server while SSH'd in as your app's system user.

chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

Researchers imagine it might be possible to transform the world’s largest desert, the Sahara, into a giant solar farm, capable of meeting four times the world’s current energy demand. Blueprints have been drawn up for projects in Tunisia and Morocco that would supply electricity for millions of households in Europe.

While the black surfaces of solar panels absorb most of the sunlight that reaches them, only a fraction (around 15 percent) of that incoming energy gets converted to electricity. The rest is returned to the environment as heat. The panels are usually much darker than the ground they cover, so a vast expanse of solar cells will absorb a lot of additional energy and emit it as heat, affecting the climate.

If these effects were only local, they might not matter in a sparsely populated and barren desert. But the scale of the installations that would be needed to make a dent in the world’s fossil energy demand would be vast, covering thousands of square kilometers. Heat re-emitted from an area this size will be redistributed by the flow of air in the atmosphere, having regional and even global effects on the climate. //

The model revealed that when the size of the solar farm reaches 20 percent of the total area of the Sahara, it triggers a feedback loop. Heat emitted by the darker solar panels (compared to the highly reflective desert soil) creates a steep temperature difference between the land and the surrounding oceans that ultimately lowers surface air pressure and causes moist air to rise and condense into raindrops. With more monsoon rainfall, plants grow and the desert reflects less of the sun’s energy, because vegetation absorbs light better than sand and soil. With more plants present, more water is evaporated, creating a more humid environment that causes vegetation to spread. //

Covering 20 percent of the Sahara with solar farms raises local temperatures in the desert by 1.5 degrees Celsius, according to our model. At 50 percent coverage, the temperature increase is 2.5 degrees Celsius. This warming is eventually spread around the globe by atmosphere and ocean movement, raising the world’s average temperature by 0.16 degrees Celsius for 20 percent coverage, and 0.39 degrees Celsius for 50 percent coverage. The global temperature shift is not uniform, though — the polar regions would warm more than the tropics, increasing sea ice loss in the Arctic. This could further accelerate warming, as melting sea ice exposes dark water which absorbs much more solar energy.

This massive new heat source in the Sahara reorganizes global air and ocean circulation, affecting precipitation patterns around the world. The narrow band of heavy rainfall in the tropics, which accounts for more than 30 percent of global precipitation and supports the rainforests of the Amazon and Congo Basin, shifts northward in our simulations. For the Amazon region, this causes droughts as less moisture arrives from the ocean. Roughly the same amount of additional rainfall that falls over the Sahara due to the surface-darkening effects of solar panels is lost from the Amazon. The model also predicts more frequent tropical cyclones hitting North American and East Asian coasts. //

Some important processes are still missing from our model, such as dust blown from large deserts. Saharan dust, carried on the wind, is a vital source of nutrients for the Amazon and the Atlantic Ocean. So a greener Sahara could have an even bigger global effect than our simulations suggested.