Sandra Henry-Stocker
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Sandra Henry-Stocker
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Unix: How random is random?
On Unix systems, random numbers are generated in a number of ways and random data can serve many purposes. From simple commands to fairly complex processes, the question “How random is random?” is worth asking.EZ random numbers If all you need is a casual list of random numbers, the RANDOM variable is an easy choice. Type "echo $RANDOM" and you'll get a number between 0 and 32,767 (the largest number that two bytes can hold).$ echo $RANDOM 29366 Of course, this process is actually providing a "pseudo-random" number. As anyone who thinks about random numbers very often might tell you, numbers generated by a program have a limitation. Programs follow carefully crafted steps, and those steps aren’t even close to being truly random. You can increase the randomness of RANDOM's value by seeding it (i.e., setting the variable to some initial value). Some just use the current process ID (via $$) for that. Note that for any particular starting point, the subsequent values that $RANDOM provides are quite predictable.To read this article in full or to leave a comment, please click here
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Unix: How random is random?
On Unix systems, random numbers are generated in a number of ways and random data can serve many purposes. From simple commands to fairly complex processes, the question “How random is random?” is worth asking.EZ random numbers If all you need is a casual list of random numbers, the RANDOM variable is an easy choice. Type "echo $RANDOM" and you'll get a number between 0 and 32,767 (the largest number that two bytes can hold).$ echo $RANDOM 29366 Of course, this process is actually providing a "pseudo-random" number. As anyone who thinks about random numbers very often might tell you, numbers generated by a program have a limitation. Programs follow carefully crafted steps, and those steps aren’t even close to being truly random. You can increase the randomness of RANDOM's value by seeding it (i.e., setting the variable to some initial value). Some just use the current process ID (via $$) for that. Note that for any particular starting point, the subsequent values that $RANDOM provides are quite predictable.To read this article in full or to leave a comment, please click here
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Unix: How random is random?
On Unix systems, random numbers are generated in a number of ways and random data can serve many purposes. From simple commands to fairly complex processes, the question “How random is random?” is worth asking.EZ random numbers If all you need is a casual list of random numbers, the RANDOM variable is an easy choice. Type "echo $RANDOM" and you'll get a number between 0 and 32,767 (the largest number that two bytes can hold).$ echo $RANDOM 29366 Of course, this process is actually providing a "pseudo-random" number. As anyone who thinks about random numbers very often might tell you, numbers generated by a program have a limitation. Programs follow carefully crafted steps, and those steps aren’t even close to being truly random. You can increase the randomness of RANDOM's value by seeding it (i.e., setting the variable to some initial value). Some just use the current process ID (via $$) for that. Note that for any particular starting point, the subsequent values that $RANDOM provides are quite predictable.To read this article in full, please click here
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Unix’s mysterious && and ||
The Unix shell’s && and || operators provide some very useful functionality, but they can be a bit mysterious, especially considering the number of options for how they are used.The most common use of these Boolean operators is in the construction of multi-conditional tests—when you want two or more conditions to be true (or any in a set of operators to be true) before some command is run. The && serves as a logical AND (requiring all conditions to be true) operation, while the || provides a logical OR (requiring only one to be true).Combining tests In the script below, we’re using && to combine two very simple conditions. We won’t get output unless both conditions are true. This particular script runs through the tests twice, but only to demonstrate the two “flavors” of the brackets that can be used. Note that && doesn’t work inside square brackets unless they’re doubled.To read this article in full or to leave a comment, please click here
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Viewing Linux output in columns
The Linux column command makes it easy to display data in a columnar format -- often making it easier to view, digest, or incorporate into a report. While column is a command that's simple to use, it has some very useful options that are worth considering. In the examples in this post, you will get a feel for how the command works and how you can get it to format data in the most useful ways.By default, the column command will ignore blanks lines in the input data. When displaying data in multiple columns, it will organize the content by filling the left column first and then moving to the right. For example, a file containing numbers 1 to 12 might be displayed in this order:To read this article in full or to leave a comment, please click here
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Viewing Linux output in columns
The Linux column command makes it easy to display data in a columnar format -- often making it easier to view, digest, or incorporate into a report. While column is a command that's simple to use, it has some very useful options that are worth considering. In the examples in this post, you will get a feel for how the command works and how you can get it to format data in the most useful ways.By default, the column command will ignore blanks lines in the input data. When displaying data in multiple columns, it will organize the content by filling the left column first and then moving to the right. For example, a file containing numbers 1 to 12 might be displayed in this order:To read this article in full or to leave a comment, please click here
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How to keep Linux from hanging up on you
When you run a command in the background on a Linux system and then log out, the process you were running will stop abruptly. If you elect to run the command with a no-hangup command, on the other hand, it will continue running and will store its output in a file.Here's how this works. The nohup command instructs your process to ignore the SIGHUP signal that would normally shut it down. That allows you to leave time-consuming processes to complete on their own without you having to remain logged in. By default, the output of the command you are running will be left in a file named nohup.out so that you can find your data the next time you log in.To read this article in full or to leave a comment, please click here
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How to keep Linux from hanging up on you
When you run a command in the background on a Linux system and then log out, the process you were running will stop abruptly. If you elect to run the command with a no-hangup command, on the other hand, it will continue running and will store its output in a file.Here's how this works. The nohup command instructs your process to ignore the SIGHUP signal that would normally shut it down. That allows you to leave time-consuming processes to complete on their own without you having to remain logged in. By default, the output of the command you are running will be left in a file named nohup.out so that you can find your data the next time you log in.To read this article in full or to leave a comment, please click here
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Improving on history
The Linux history command allows users to repeat commands without retyping them and to look over a list of commands that they've recently used, but that's just the obvious stuff. It is also highly configurable, allows you to pick and choose what you reuse (e.g., complete commands or portions of commands), and control what commands are recorded. In today's post, we're going to run through the basics and then explore some of the more interesting behaviors of the history command.The basics Typing "history" and getting a list of previously entered commands is the command's most obvious use. Pressing the up arrow until you reach a command that you want to repeat and hitting enter to rerun it is next. And, as you probably know, you can also use the down arrow. In fact, you can scroll up and down your list of previously entered commands to review them or rerun them.To read this article in full or to leave a comment, please click here
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Improving on history—the Linux history command, that is
The Linux history command allows users to repeat commands without retyping them and to look over a list of commands they've recently used, but that's just the obvious stuff. It is also highly configurable, allows you to pick and choose what you reuse (e.g., complete commands or portions of commands), and controls what commands are recorded.In today's post, we're going to run through the basics and then explore some of the more interesting behaviors of the history command.The basics of the Linux history command Typing "history" and getting a list of previously entered commands is the command's most obvious use. Pressing the up arrow until you reach a command that you want to repeat and hitting enter to rerun it is next. And, as you probably know, you can also use the down arrow. In fact, you can scroll up and down your list of previously entered commands to review them or rerun them.To read this article in full or to leave a comment, please click here
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Improving on history—the Linux history command, that is
The Linux history command allows users to repeat commands without retyping them and to look over a list of commands they've recently used, but that's just the obvious stuff. It is also highly configurable, allows you to pick and choose what you reuse (e.g., complete commands or portions of commands), and controls what commands are recorded.In today's post, we're going to run through the basics and then explore some of the more interesting behaviors of the history command.The basics of the Linux history command Typing "history" and getting a list of previously entered commands is the command's most obvious use. Pressing the up arrow until you reach a command that you want to repeat and hitting enter to rerun it is next. And, as you probably know, you can also use the down arrow. In fact, you can scroll up and down your list of previously entered commands to review them or rerun them.To read this article in full or to leave a comment, please click here
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What the jot command can do for you
The jot command has been around for ages, but remains one of those interesting commands that a lot of Linux users never get around to using. It can be very handy in scripts as well as on the command line by generating number or character sequences, even pseudo-randomly.In its simplest form, the jot command generates a simple sequence of numbers from 1 to your selected maximum.$ jot 5 1 2 3 4 5 You can stick the jot command output into simply by redirecting it.$ jot 5 > five $ cat five 1 2 3 4 5 If you want to start with some number other than 1, you just use a slightly different syntax. The command “jot 5 11”, for example, would create a list of five numbers starting with 11.To read this article in full or to leave a comment, please click here
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Dealing with NIST’s about-face on password complexity
NIST's new guidelines for password complexity have reversed many of rules on what defines a good password
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Dealing with NIST’s about-face on password complexity
In the last few years, we've been seeing some significant changes in the suggestions that security experts are making for password security. While previous guidance increasingly pushed complexity in terms of password length, the mix of characters used, controls over password reuse, and forced periodic changes, specialists have been questioning whether making passwords complex wasn't actually working against security concerns rather than promoting them.Security specialists have also argued that forcing complexity down users' throats has led to them writing passwords down or forgetting them and having to get them reset. They argued that replacing a password character with a digit or an uppercase character might make a password look complicated, but does not actually make it any less vulnerable to compromise. In fact, when users are forced to include a variety of characters in their passwords, they generally do so in very predictable ways. Instead of “password”, they might use “Passw0rd” or even “P4ssw0rd!”, but the variations don't make the passwords significantly less guessable. People are just not very good at generating anything that's truly random.To read this article in full or to leave a comment, please click here
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Eight steps to the GDPR countdown
With only one year until this business-changing regulation goes into effect, it's time for companies to start planning their approach. Let's run through eight steps you can take to be ready.
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Eight steps to the GDPR countdown
One year from today, the recently passed regulation known as “GDPR” (General Data Protection Regulation) goes into effect. While EU-specific, it can still dramatically affect how businesses that work with personal data of citizens and residents of the EU. GDPR was approved a year ago and will be going into effect in another year. It applies directly to organizations within the EU, but also applies to organizations outside the EU if they 1) offer goods and services to the EU, 2) monitor the behavior EU subjects, or 3) process or retain personal data of EU citizens and residents. And the regulation can place very serious fines and sanctions for non-compliance.To read this article in full or to leave a comment, please click here
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The complexity of password complexity
Password complexity settings on Linux systems is a lot more interesting -- and complex -- than it might appear.
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The complexity of password complexity
Deploying password quality checking on your Debian-base Linux servers can help to ensure that your users assign reasonable passwords on their accounts, but the settings themselves can be a bit misleading. For example, setting a minimum password length of 12 characters does not mean that your users' passwords will all have twelve or more characters. Let's stroll down Complexity Boulevard and see how the settings work and examine some settings worth considering.First, if you haven't done this already, install the password quality checking library with this command:apt-get -y install libpam-pwquality The files that contain most of the settings we're going to look at will be:To read this article in full or to leave a comment, please click here
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The complexity of password complexity
Deploying password quality checking on your Debian-base Linux servers can help to ensure that your users assign reasonable passwords on their accounts, but the settings themselves can be a bit misleading. For example, setting a minimum password length of 12 characters does not mean that your users' passwords will all have twelve or more characters. Let's stroll down Complexity Boulevard and see how the settings work and examine some settings worth considering.First, if you haven't done this already, install the password quality checking library with this command:apt-get -y install libpam-pwquality The files that contain most of the settings we're going to look at will be:To read this article in full or to leave a comment, please click here
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The complexity of password complexity
Deploying password quality checking on your Debian-base Linux servers can help to ensure that your users assign reasonable passwords on their accounts, but the settings themselves can be a bit misleading. For example, setting a minimum password length of 12 characters does not mean that your users' passwords will all have twelve or more characters. Let's stroll down Complexity Boulevard and see how the settings work and examine some settings worth considering.First, if you haven't done this already, install the password quality checking library with this command:apt-get -y install libpam-pwquality The files that contain most of the settings we're going to look at will be:To read this article in full, please click here