Tag Archives: ipv6

sage on ipv6.he.net


This was really fun!

If you complete this with your own domain and server you’ll learn to set up these:

  • set up IPv6 address and routing
  • point your DNS to the IPv6 address – this would applies mostly if you have your own nameserver
  • point the IPv6 address to the DNS – rDNS – requires quite long entries!
  • set up e-mail – both receiving (imap/pop3) and sending (smtp)
  • slightly more advanced use of dig :)

The e-mail part was the trickiest for me as I hadn’t done that before. Used courier and exim4 to set this up on a Debian Virtual Machine.


Do you have IPv6 connectivity? Perhaps a server and a domain name already set up?


Some things you get to play with:

  • check if you can view the page in IPv6
  • send an e-mail over IPv6
  • rDNS over IPv6

Quite fun way of learning about IPv6

Red Hat Certification – RHCE – Course Outline


In case you saw my previous posts I’ve been prepping for a RHCE course the last couple of weeks.

Here are the posts based on the objectives:

Odds are quite high that I’ve missed something or not gone deep enough into some subjects and for the record some subjects I decided to skip.

I’m taking the course over at Tieturi here in Helsinki and they have published the schedule for the course, with quite detailed outline.

This outline of the course can with benefit be used to see if you missed any terms or functions while going through the objectives.

I’ll go through the ones I find more interesting below:

Network Resource Access Controls

-Internet Protocol and Routing

OK, well this is quite obvious, some commands:

ip addr
ip route
route add
netstat -rn


-IPv6: Dynamic Interface Configuration
-IPv6: StaticInterface Configuration
-IPv6: Routing Configuration

You can add IPV6 specific lines in the ifcfg-device files in /etc/sysconfig/network-scripts/. See /usr/share/doc/initscripts*/sysconfig

Some settings can also go into /etc/sysconfig/network


Netfilter Overview
-Rules: General Considerations
Connection Tracking
-Network Address Translation (NAT)
-IPv6 and ip6tables


Web Services

-Squid Web Proxy Cache

On client check what IP you get:

curl --proxy squid-server.example.com:3128 www.guldmyr.com/ip.php

On server install and setup squid:

yum install squid
vi /etc/squid/squid.conf
#add this line in the right place:
acl localnet src
#allow port 3128 TCP in the firewall (use very strict access here)
service squid start

On client:

curl --proxy squid-server.example.com:3128 www.guldmyr.com/ip.php

Beware that this is unsecure. Very unsecure. You should at least set up a password for the proxy, change the default port and have as limited firewall rules as possible.

E-mail Services

-Simple Mail Transport Protocol
-Sendmail SMTP Restrictions
-Sendmail Operation


Securing Data

-The Need For Encryption

-Symmetric Encryption

Symmetric uses a secret/password to encrypt and decrypt a message.
You can use GnuPG (cli command is ‘gpg’) to encrypt and decrypt a file symmetrically. Arguments:

–symmetric/-c == symmetric cipher (CAST5 by default)
–force-mdc == if you don’t have this you’ll get “message was not integrity protected”

There are many more things you can specify.

echo "awesome secret message" > /tmp/file
gpg --symmetric --force-mdc /tmp/file
#(enter password)
#this creates a /tmp/file.gpg
#beware that /tmp/file still exists
#to decrypt:
gpg --decrypt /tmp/file.gpg
gpg: 3DES encrypted data
gpg: encrypted with 1 passphrase
awesome secret message


-Asymmetric Encryption

Uses a key-pair. A public key and a private key.
A message encrypted with the public key can only be decrypted with the private key.
A message encrypted with the private key can only be decrypted with the public key.

GnuPG can let you handle this.

Login with a user called ‘labber’:

gpg --gen-key
# in this interactive dialog enter username: labber, e-mail and password
# this doesn't always work, might take _long_time_, eventually I just tried on another machine
echo "secret message" > /tmp/file
gpg -e -r labber /tmp/file
# enter password
gpg --decrypt /tmp/file
# enter password

To export the public key in ASCII format you can:

gpg --armor --output "key.txt" --export "labber"

However, how to encrypt a file with somebody else’s public key?

-Public Key Infrastructures – PKI

Consists of:

  • CA – certificate authority – issues and verifies digital certiciates
  • RA – registration authoriy – verifies user identity requesting info from the CA
  • central directory – used to store and index keys

-Digital Certificates

A certificate has user details and the public key.

Account Management

-Account Management
-Account Information (Name Service)
Name Service Switch (NSS)
Pluggable Authentication Modules (PAM)
-PAM Operation
-Utilities and Authentication



Basically a way to authenticate users. You can put different types of authentication ways behind PAM. So that a software only needs to learn to authenticate to PAM and then PAM takes care of the behind-the-scenes-work.

For example you can have PAM connect to an ldap-server.

CLI: authconfig



HEPIX Spring 2011 – Day 3

Day 3 woop!

An evaluation of gluster: uses distributed metadata, so no bottleneck that comes with a metadata server, can or will do do some replication/snapshot.

Virtualization of mass storage (tapes). Using IBM’s TSM (Tivoli Storage Manager) and ERMM. Where ERMM manages the libraries, so that TSM only sees the link to the ERMM. No need to set up specific paths from each agent to each tape drive in each library.
They were also using Oracle/SUN’s T10000c tape drives that goes all the way up to 5TB – which is quite far ahead of LTO consortium’s LTO-5 that only goes to 1.5/3TB per tape. Some talk about buffered tape marks which speeds up tape operations significantly.

Lustre success story at GSI. They have 105 servers that provide 1.2PB of storage and max throughput seen is 160Gb/s. Some problems with

Adaptec 5401 – boots longer than entire linux. Not very nice to administrate. Controller complains about high temps – and missing fans of non-existing enclosures. Filter out e-mails with level “ERROR” and look at the ones with “WARNING” instead.

Benchmarking storage with trace/replay. Using strace (comes default with most Unixes) to record some operations and the ioreplay to replay them. Proven to give very similar workloads. Especially great for when you have special applications.

IPv6 – running out of IPv4 addresses, when/will there be sites that are IPv6? Maybe if a new one comes up? What to do? Maybe collect/share IPv4 addresses?

Presentations about the evolve needed of two data centers to accomodate requirements of more resource/computing power.

Implementing ITIL with Service-Now (SNOW) at CERN.

Scientific Linux presentation. Live CD can be found here:

www.livecd.ethz.ch. They might port NFS 4.1 that comes with Linux Kernel 2.6.38 to work with SL5. There aren’t many differences between RHEL and SL but in SL there is a tool called Revisor, which can be used to create your own linux distributions/CDs quite easily.


Errata is a term – this means security fixes.

Dinner later today!


Next Days:
Day 5
Day 4

Previous Days:
Day 2
Day 1

HEPIX Spring 2011

I’m heading to Hepix this whole week!

Looks like there’s some really interesting topics like:

Lustre, glustre, ipv6, stuff about the CERN it facilities, Scientific Linux report, cloud/grid virtualization, Oracle Linux.

I’ll sure be doing a bit of blogging about what’s going down.