Sep 302014
 

tux-terminal.jpg
Article by Daniel Miessler first posted on his blog

lsof is the sysadmin/security über-tool. I use it most for getting network connection related information from a system, but that’s just the beginning for this powerful and too-little-known application. The tool is aptly called lsof because it “lists openfiles“. And remember, in UNIX just about everything (including a network socket) is a file.

Interestingly, lsof is also the Linux/Unix command with the most switches. It has so many it has to use both minuses andpluses.

usage: [-?abhlnNoOPRstUvV] [+|-c c] [+|-d s] [+D D] [+|-f[cgG]]
 [-F [f]] [-g [s]] [-i [i]] [+|-L [l]] [+|-M] [-o [o]]
 [-p s] [+|-r [t]] [-S [t]] [-T [t]] [-u s] [+|-w] [-x [fl]] [--] [names]

As you can see, lsof has a truly staggering number of options. You can use it to get information about devices on your system, what a given user is touching at any given point, or even what files or network connectivity a process is using.

For me, lsof replaces both netstat and ps entirely. It has everything I get from those tools and much, much more. So let’s look at some of its primary capabilities:

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Aug 292014
 

If you manage a server with many different users or just your family computer you will probably have many different accounts to manage, and one important aspect of any account it’s its password.

In this small article I’ll show you how to use the basic passwd command but also how to do some small bash script or use a web application, if you have a more complex environment, such as a central ldap server that keep all your accounts information.
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Aug 132014
 

Article by giannis_tsakiris first posted on http://www.giannistsakiris.com

A hard link is actually nothing more than a regular directory entry, which in turn can be seen as a pointer to the actual file’s data on the disk. The cool thing about hard-links is that a file can be stored once on the disk, and be linked to multiple times, from different locations/entries, without requiring to allocate extra disk space for each file instance.

But then a question arises: Given a specific file on disk, how can someone know whether it is linked to by other directory entries or not? This can be easily answered using the ls command:

giannis@zandloper:/etc$ ls -l passwd
-rw-r--r-- 1 root root 1402 2008-03-30 17:49 passwd
;

Do you ever wonder what is this small number between the file permissions and the owner in the output of ls’s long listing format (its value is usually “1″ for files, or “2″ for directories)? This number is actually the link-count of the file, when referring to a file, or the number of contained directory entries, when referring to a directory (including the . and .. entries).
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Linux Terminal: Reptyr attach a running process to a new terminal

If, like me, you work on terminals connected via ssh to remote computer/server you are probably used to tmux and screen and so it’s not a problem if you have to close your session, as you’ll be able to easily re-connect when you need it, but sometimes you could forget about using one of these [...]

Linux Terminal: inxi – a full featured system information script

Sometimes it’s useful to know which components you are using on a GNU/Linux computer or server, you can go with the long way, taking a look at the boot message for all the hardware discovered, use some terminal commands such as lsusb,lspci or lshw or some graphical tools such as hardinfo (my favourite graphical tool) [...]