Monday, October 13, 2008

Kernel versions on different RHELs...

note to self

When ever you need to find out a kernel version of a particular RHEL version or an update, you can head over to this Knowledge Base Article. Hope they are keeping it up-to-date.

Below is what it contains right now.

Red Hat Enterprise Linux
Update v. 2.1 v. 3 v. 4 v. 5
GA 2.4.9-e.3 2.4.21-4 2.6.9-5 2.6.18-8
U1 2.4.9-e.12 2.4.21-9 2.6.9-11 2.6.18-53
U2 2.4.9-e.24 2.4.21-15 2.6.9-22 2.6.18-92
U3 2.4.9-e.34 2.4.21-20 2.6.9-34 -
U4 2.4.9-e.40 2.4.21-27 2.6.9-42 -
U5 2.4.9-e.49 2.4.21-32 2.6.9-55 -
U6 2.4.9-e.57 2.4.21-37 2.6.9-67 -
U7 - 2.4.21-40 2.6.9-78
U8 - 2.4.21-47 - -
U9 - 2.4.21-50 - -

Old CentOS/RHEL packages

note to self

When there is a need for an old RHEL or CentOS rpm, head over to They keep an archive of package trees of previous CentOS releases.

It can not be used as a yum repo, but its good enough if you know what you need exactly. The security updates are not put in there, but this works for me..


Thank You CentOS.! :)

its rpm-build NOT rpmbuild..!

note to self

"rpmbuild" is the tool used to build rpms ( something like a .deb in Debian flavours ). Whenever i want to build a rpm on a system where i don't have rpmbuild installed, its quite easy to get it installed on the system using "yum".

The problem ( - not exactly a problem, just something that keeps on happening to me ) is that when i do "yum install rpmbuild" yum doesn't output what i need. Instead it outputs stuff which are not really even related to my requirement. The program that provides rpmbuild is named "rpm-build", which keeps causing me this problem. :(

The packages given as results from yum, when the query string is given as "rpmbuild", all seem to have the word "rpmbuild" on their "info" meta data, but its strange, and quite frankly annoying that "rpm-build" ( the actual package that provides "rpmbuild" ) doesn't have the key "rpmbuild" which could be the reason for this.

And, before i forget, the correct way would be "yum install rpm-build" :)
I hate that i keep forgetting these.!!!

Monday, October 06, 2008

my favorite superhero...

Something i enjoy going through.
-from the movie "Kill Bill - vol.2"


i find the whole mythology surrounding superheroes fascinating.
take my favorite superhero, Superman.
Not a great comic book. Not particularly well-drawn.

But the mythology..

The mythology is not only great, it's unique.

Now, a staple of the superhero mythology is,
there's the superhero and there's the alter ego.

Batman is actually Bruce Wayne, Spider-Man is actually Peter Parker.

When that character wakes up in the morning, he's Peter Parker.
He has to put on a costume to become Spider-Man.

And it is in that characteristic Superman stands alone.

Superman didn't become Superman. Superman was born Superman.

When Superman wakes up in the morning, he's Superman.

His alter ego is Clark Kent.

His outfit with the big red "S" - that's the blanket he was wrapped in as a baby when the Kents found him.

Those are his clothes.

What Kent wears - the glasses, the business suit - that's the costume. That's the costume Superman wears to blend in with us.
Clark Kent is how Superman views us.

And what are the characteristics of Clark Kent?

He's weak... ...he's unsure of himself... ...he's a coward.

Clark Kent is Superman's critique on the whole human race.


bunch of yellow...

bunch of yellow, originally uploaded by Yajith.

Friday, October 03, 2008

port forwarding using ssh

note to self

ssh can be used in the below way to forward traffic over a secure channel, to make otherwise un-secure ( plain ) traffic to be encrypted.

ssh access to the destination sever is required for this to work.

For an example, to secure POP3 communications with a mail server at a.b.c.d one can do something like below on their local machine.

ssh -N -f -L user@a.b.c.d

-f is to put the connection to the background
-N to wait infinitely for incoming connections
-L binds the tunnel to the specified port ( 1100 in this case )

this will create a ssh tunnel bound to the local port 1100 with port 110 of a.b.c.d
@a.b.c.d performs the authentication via ssh with the a.b.c.d

once this is done, the POP client can be re-configured to talk to local port 1100. ssh will happily encrypt and decrypt what you put in the tunnel from the end-points. This mechanism can be used to secure systems that are not built with such capabilities.

when you want to stop the tunnel, you can simply use "kill"


FAQ at was quite helpful in figuring this out. thanks bud for pointing out such things can be easily done with ssh. :)