Recently in the howtos Category

IPV6 migration part 1

The first step in my exploration of IPV6 was to get an IPV6 address via an IPV4 to IPV6 tunnel. A little research lead me to the fine folks at SixXS.

Learn IPV6 migration

In the coming weeks or months I will be posting my experiences testing IPV6 and hopefully migrating to IPV6 Internet services, including this website. I hope you will return here and learn from my experiences.

Cfengine 3 tutorial

Multipathd testing

  1. Format and mount the SAN LUN.
  2. Start a write to the mounted filesystem cat /dev/zero >> /pathto/mnt/testfile &
  3. Now connect to the multipath daemon in interactive mode multipathd -k
  4. View current paths with show maps topology
    multipathd> show maps topology
    reload: mpath5 (360060e801045249004f2a5f900000031) dm-7 HITACHI,DF600F
    [size=128G][features=0][hwhandler=0][rw]
    \_ round-robin 0 [prio=1][active]
     \_ 1:0:0:4 sdb 8:16  [active][ready]
    \_ round-robin 0 [prio=0][enabled]
     \_ 2:0:0:4 sdc 8:32  [active][ready]
    
  5. There are two paths shown as sdb and sdc. Delete one path.
    del path sdb
  6. Suspend with ctrl-z and check that the write is still happening.
    ls -l /pathto/mnt If testfile is still growing then the path sdc is working.
  7. Resume multipath with fg 2. Re-add the path.
    add path sdb
  8. Now remove the other path.
    del path sdc
  9. Again suspend iwth ctrl-z and check that the test file is growing. If so then resume multipath and re-add the path.
    add path sdc
  10. Testing complete. Exit with ctrl-c. Kill the write job with kill %1. Remove the test file.

Linux networking cheatsheet

Network calculation
Show network info ipcalc 10.0.0.0/24
ipcalc 10.0.0.0/255.255.255.0
Segment network into 2 50 node subnets ipcalc 10.0.0.0/24 -s 50 50

Net-tools versus Iptroute2
List interfaces ip addr list
ifconfig -a
ip addr list eth0
ifconfig eth0
Link status ip link list
ifconfig -a
ip link list eth0
ifconfig eth0
Route table ip route
netstat -rn
Adding routes ip route add default via 10.0.0.1
Add/delete IP addresses ip addr add 10.0.0.2/24 dev eth0
ifconfig eth0 10.0.0.2 netmask 255.255.255.0
ip addr del 10.0.0.2/24 dev eth0
ifconfig eth0 del 10.0.0.2

Linux Ethernet bonding

# Loading module:
# for Red Hat AS4, may work with other 2.6 Linuxes.
install bond0 /sbin/modprobe bonding -o bond0 mode=0 miimon=100
# for Red Hat AS3, may work with other 2.4 Linuxes.
alias bond0 bonding
options bond0 -o bonding mode=0 miimon=100
# For Redhat distributions
# ifcfg-ethx
DEVICE=ethx
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none

# ifcfg-bond0
DEVICE=bond0
USERCTL=no
ONBOOT=yes
IPADDR=172.16.48.66
NETMASK=255.255.255.0
GATEWAY=172.16.48.1
Click for more Ethernet bonding information.

OSI model diagram

osi-model.gif

Cfengine 2 cookbook

This entry offers solutions to system administration problems using the configuration management tool Cfengine 2. Cookbook now available for Cfengine 3.

Clustering with Red Hat

This entry presents an overview of how to build a DB2 service cluster using the Red Hat Cluster Suite. This procedure can be useful in learning how to setup clusters for other services.