Neil H Watson, Linux consultant

Contents

• Overview
  • What is Cfengine?
  • Client/Server architecture
  • Directories and files
  
  
• Basic example
  • Installation
  • Initial setup
  
  
• Other examples
  • Editing files
  • Disabling files
  • Disabling processes
  
  
• Further reading

Many believe that open source projects cannot be used in the enterprise because of the lack of support. This is untrue.

To maintain the large quantity of servers typically found in enterprise organizations, systems administration must move beyond manual and custom scripts toward a centralized configuration management service. This move can save an organization considerable time and money.

The following may not apply to all shells.

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 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

OSI model diagram

Whether realizing it or not every organization goes through the process of selecting a naming convention. Often this is done without much forward planing resulting in unwieldy host and service names. In the worst cases host names are dropped completely and either by habit or lack of a proper DNS service only ip addresses are used.

In the following I will talk about the different types of naming conventions that I’ve experienced or read about. I’ll discuss the pros and cons of each. Before we get to that we’ll need to have a small refresher on domain name services.