Friday 14 September 2012

Meaning of /etc, /usr in Linux?

In my career, I have come across many people who have described the acronyms /etc, and /usr in very different ways. However, for all other purposes, all the users and Linux community generally agree on the use intended or otherwise, of these filesystem hierarchy levels.
The discussions that i have heard goes like so:

/usr


/usr: "user". , eg. /usr/bin is for general user binaries, /usr/doc and /usr/share/doc

Actually, /usr stands for Unix System Resources.

/usr usually contains by far the largest share of data on a system. Hence, this is one of the most important directories in the system as it contains all the user binaries, their documentation, libraries, header files, etc.... X and its supporting libraries can be found here. User programs like telnet, ftp, etc.... are also placed here. In the original Unix implementations, /usr was where the home directories of the users were placed (that is to say, /usr/someone was then the directory now known as /home/someone). In current Unices, /usr is where user-land programs and data (as opposed to 'system land' programs and data) are. The name hasn't changed, but it's meaning has narrowed and lengthened from "everything user related" to "user usable programs and data". As such, some people may now refer to this directory as meaning 'User System Resources' and not 'user' as was originally intended.

usr stands for "user-specific resources" and it fits quite nicly i think. it might be other abbreviations that is used with "usr" though, but i wouldnt know about them other then the ones ive read in this thread

According to linux-training.be/files/books/html/fun/ch09s08.html, it stands for Unix System Resources.

/usr - The secondary hierarchy which contain its own bin and sbin sub-directories.


/etc

 '/etc' is indeed an acronym and stands for "Editable Text Configuration".

Yes, etc stands for "etcetera" It's purpose in life is to host various configuration files from around your system.

Probably not the official meaning, but I have seen etc referred to as "editable text configuration".

it means the simple 'etcetera'

it means 'extended tool chest' per this gnome mailing list entry or per this Norwegian article.

"editable text configurations" is a stupid name too, because if it's text, it's evidently editable. So why not just "text configurations" then? Also, in early Unix, everything was editable (remember, in Unix, everything is a file), so that's superfluous too. And, lastly, it was the repository for a lot of things that weren't configurations, including binaries.

So whats your take on these!

Monday 10 September 2012

Fixed RHEL/Centos 5 rpms for net-snmp-5.3.2.2-17 gpfs support

As raised in bug note 707912 ( https://bugzilla.redhat.com/show_bug.cgi?id=707912)
where net-snmp does not see mounted xfs filesystems, the shipped net-snmp-5.3.2.2-17 in the Centos 5.8 tree (and probably later versions in RHEL6 as well) does not support gpfs filesystems either.
The implication is that those who are upgrading from earlier versions (e.g. from Centos 5.5 to 5.8) will lose snmp monitoring of gpfs filesystems.
All the versions in the Centos 5.8 tree are broken. The only way to address the issue is to upgrade to a later tree (e.g. to Centos 6.3) or to build from source or to use third-party rpms.
I have managed to patch and rebuild the shipped net-snmp-5.3.2.2-17.x86_64.rpm and that has proved to be an easier, low risk alternative.
Those who may need to reuse my binaries are herehere & here
~]# yum remove net-snmp net-snmp-libs
~]# rpm -Uvh net-snmp-libs-5.3.2.2-17.x86_64.rpm
~]# rpm -Uvh net-snmp-5.3.2.2-17.x86_64.rpm
~]# rmp -Uvh net-snmp-utils-5.3.2.2-17.x86_64.rpm
~]# yum install OpenIPMI (re-install if you had removed it as dependent in first command)