Book Review: Linux iptables Pocket Reference


Linux iptables Pocket Reference (Paperback)

By (author): Gregor N. Purdy

Firewalls, Network Address Translation (Nat), network logging and accounting are all provided by Linux's Netfilter system, also known by the name of the command used to administer it, iptables. The iptables interface is the most sophisticated ever offered on Linux and makes Linux an extremely flexible system for any kind of network filtering you might do. Large sets of filtering rules can be grouped in ways that makes it easy to test them and turn them on and off. Do you watch for all types of Icmp traffic-some of them quite dangerous? Can you take advantage of stateful filtering to simplify the management of Tcp connections? Would you like to track how much traffic of various types you get? This pocket reference will help you at those critical moments when someone asks you to open or close a port in a hurry, either to enable some important traffic or to block an attack. The book will keep the subtle syntax straight and help you remember all the values you have to enter in order to be as secure as possible. The book has an introductory section that describes applications, followed by a reference/encyclopaedic section with all the matches and targets arranged alphabetically.
List Price: $9.95 USD
New From: $4.96 USD In Stock
Used from: $4.55 USD In Stock



Linux iptables Pocket Reference (Paperback)

By (author): Gregor N. Purdy

List Price: $9.95 USD
New From: $4.96 USD In Stock
Used from: $4.55 USD In Stock

I've just read a really useful book on iptables: Linux iptables Pocket Reference.

It's a great reference book which is quite short but packed with more details than you'll ever want to know.

For my review of this book, please read the post on Books @ UnixTutorial website: Linux iptables Pocket Reference review.

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Welcome to the all new Unix Tutorial!

Hey guys, just wanted to let you know that Unix Tutorial is now sporting a modern theme that will make it even easier to find and read articles on different topics.

Unix Tutorial Priorities for 2014 so far

  • finish the Unix Tutorial: Guide to SSH
  • expand the Unix Glossary section
  • write more about OSX command line

Anyone has more ideas? Please leave a comment so that I know!

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How To Confirm Mac OS Version from Command Line

Just a very quick tip today, I stumbled upon this command a while ago and think it may be handy for someone learning the OSX command line.

By using sw_vers command, you can easily confirm the exact version of your Mac OS and the product code (build version) of it:

macbook:~ root# sw_vers
ProductName: Mac OS X
ProductVersion: 10.8.2
BuildVersion: 12C2034

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Questionnaire for my upcoming Linux Administration ebook

If you're planning to acquire or expand Linux System Administration skills anytime soon, you may find my upcoming Linux Pro: How To Make a Great Career in Systems Administration ebook really useful.

Although I have most of my Linux ebook structure planned already, I would really like to take all the feedback I can get and make the book as useful as you want it to be.

Please take 10min to complete the survey, and if you specify your valid email address I'll be sure to give you a 50% discount when the ebook is available: Linux Pro: eBook Questionnaire. Thanks!

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3 Ways to List Groups for a User in Linux

Okay, today's post will be the back-to-basics style, but to make it more interesting I've come up with as many (reasonable) ways to list groups of a Linux user as possible. As always, these commands are actually quite universal, so will likely work in most Unix and Unix-like flavours.

Using the groups command to list groups for a user

This is probably the most obvious way of getting the job done. Simply type "groups" followed by a username and you will get the list of all the groups that user belongs to:

greys@ubuntu$ groups greys
greys : greys adm dialout cdrom plugdev lpadmin sambashare admin

Now, as you noticed, I'm confirming my own groups (running groups greys as user greys), so this means that we can omit the longer form shown above and simply type "groups" to get the same result:

greys@ubuntu$ groups
greys : greys adm dialout cdrom plugdev lpadmin sambashare admin

Using id command to identify Unix groups for a user

Another way to confirm groups is to use the id command, it's very simple and I tend to use this approach in most case.

Here's how using the id command will look like:

greys@ubuntu$ id greys
uid=1000(greys) gid=1000(greys) groups=1000(greys),4(adm),20(dialout),24(cdrom),46(plugdev),115(lpadmin),116(sambashare),117(admin)

Looking into /etc/group file to confirm groups for a user

This last approach may be helpful when the above things don't work. I tend to use it for another indirect benefit – comparing a user's group membership against other users.

What you do for this situation is simply grep for a username in the /etc/group file:

greys@ubuntu$ grep greys /etc/group
adm:x:4:greys
dialout:x:20:greys
cdrom:x:24:greys
plugdev:x:46:greys
greys:x:1000:
lpadmin:x:115:greys
sambashare:x:116:greys
admin:x:117:greys

Bonus: confirming groups for a user using getent

This last approach will help you confirm the group membership regardless of where your usernames/passwords and groups are stored. As you know, they are most often local to your Unix system, but sometimes can be managed using NIS/NIS+ or LDAP.

So here's a universal way for listing groups for a user, it relies on the getent command:

greys@ubuntu$ getent group | grep greys
adm:x:4:greys
dialout:x:20:greys
cdrom:x:24:greys
plugdev:x:46:greys
greys:x:1000:
lpadmin:x:115:greys
sambashare:x:116:greys
admin:x:117:greys

That's it for today, thanks for your time and hope I made it worthwhile!

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Puppet 3.0.0 is here

As some of you may have noticed already, Puppet configuration management system has just been upgraded to 3.0.0 release.

Being a major milestone, this upgrade brings the following major improvements:

  • performance is much better for catalog compilation
  • improved and expanded OS support – lots of Windows improvements, great new functionality for Solaris (zones, packages and services are finally supported now)
  • pluginsync is now enabled by default
  • new version of Ruby is supported (Ruby 1.9) and Ruby DSL was completely rewritten
  • dynamic scoping is no longer supported (yep, this breaks backwards compatibility with 2.7.x branch of Puppet)
If you're new to Puppet, please visit the PuppetLabs website for more info and for free download.

I have read and reviewed a couple of great books on Puppet, so check the reviews out:

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How To Mount DMG Files from Command Line in Mac OS

DMG files are proprietary disk image files used for software distribution in Mac OS. Providiing both password protection and bzip2-like compression, these files are perfect packaging medium.

Usually DMG files are opened automatically when you click them in Finder. They appear as a folder with files, but actually Finder mounts each DMG file as a separate filesystem and then shows you its contents. If you're observant enough, you'll see that in the left side panell of Finder you have all the active DMG filesystems listed and ready to be ejected once you finish copying the files or installing new software.

Sometimes you may want to download and mount DMG file using Mac OS command line, and in this post I'll show you how to do it

[Read more...]

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Are you a CentOS user? Will you switch to Oracle Linux?

Have recently found out that Oracle Linux is now completely free to get and to use, meaning that you'll only have to pay for commercial support should you decide you need it.

Oracle has even gone as far as create a special page converting CentOS users into Oracle Linux followers: Oracle Linux – A better alternative.

What do you think?

Will you be switching?

Have you tried it yet?

Let me know in the commetns area, thanks!

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Book Review: Learning MySQL

If you follow UnixTutorial on Facebook you've probably seen my short port a few weeks back announcing the UnixTutorial side project: Books @ UnixTutorial.

My first review has been online for a while, so check it out:  Learning MySQL.

More reviews are coming, expect at least one new review a week for the years to come! I plan on reviewing books but will write a few of my own if I'm stuck for new material or pressed for some Unix basics to be shared.

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Using Dropbox with Unix

Although last week saw some pretty exciting developments in the cloud storage (Google Drive announcement and SkyDrive free 25Gb space), the truth is that Dropbox is still the king of the cloud storage hill – it's hands down the easiest to use and integrate.

I've been a Dropbox user for a few years now, but have started using it actively only in the last 12 months or so. It's been an invaluable tool for me thanks to its integration with 1Password, the password tool of my choice. Dropbox also helps with lots of day-to-day tasks and thats why I decided it's time to share some of the tips.

Having used Dropbox extensively on Windows systems (XP on laptop and Win7 on desktops), I've recently moved on to using Dropbox with my Mac OSX desktop and Linux hosting.

So here are the top tips for using Dropbox with Unix – each one does wonders for me and so I hope you like them as well.

Important: If you're not a Dropbox user yet, please use this link to sign up – it means I'll get a small bonus (extra 500MB to my free account) for referring you.

[Read more...]

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