Category Archives: Technology

Posted By : Graham Carmichael 19 Jun

Script to check if something else is running.

This is a simple script to check that something else is still running and if not start it up again.

[bash]

#!/bin/sh
SERVICE=’mqtt3′

if ps ax | grep -v grep | grep $SERVICE > /dev/null
then
echo "$SERVICE service running, everything is fine"
else
echo "$SERVICE is not running"
# echo "$SERVICE is not running!" | mail -s "$SERVICE down" root
nohup /usr/bin/python3 /home/pi/bin/mqtt3.py &

fi

[/bash]

Posted By : Graham Carmichael 15 Jun

crontab

@reboot crontab directive only actually fires if its applied against the root account.

It makes some sort of sense, however no real technical reason that I can see.

Posted By : Graham Carmichael 1 Sep

Beeping WD PIDrive 314GB

Turn off

After my system boot:

[dinux@alarmpi ~]$ sudo hdparm -B /dev/sda1
/dev/sda1:
APM_level = 128

Then i set -B value to 255

sudo hdparm -B 255 /dev/sda1

Check again:

[dinux@alarmpi ~]$ sudo hdparm -B /dev/sda1
/dev/sda1:
 APM_level	= off

Posted By : Graham Carmichael 10 Dec

National Grid Battery

So we know the issue, green energy is not consistent or might not be available when its actually needed so we need some really massive batteries on the national grid so we don’t have to turn on or up the dirty power stations.

So far we have hydro, so when the demand on the grid is less then the generation capacity we can pump water up into upper elevation reservoirs and when the power is required it drops to the lower reservoirs to generate hydro electricity.

Now we have a new battery, is called cryogenic storage. Its uses excess generation capacity to chill air and when the power is required the warming air expands and drives the turbines.

See

http://www.bbc.co.uk/news/science-environment-37902773

We need more of this sort of thing.

Posted By : Graham Carmichael 7 Nov

Flexible Single Master Operation Roles (FSMO)

Flexible Single Master Operation Roles (FSMO)

Active Directory has five special roles which are vital for the smooth running of AD as a multimaster system. Some functions of AD require there is an authoritative master to which all Domain Controllers can refer to. These roles are installed automatically and there is normally very little reason to move them, however if you de-commission a DC and DCPROMO fails to run correctly or have a catastrophic failure of a DC you will need to know about these roles to recover or transfer them to another DC.

The forest wide roles must appear once per forest, the domain wide roles must appear once per domain.

The Roles

There are five FSMO roles, two per forest, three in every Domain. A brief summary of the role is below.

Forest Wide Roles:

• Schema Master

The schema is shared between every Tree and Domain in a forest and must be consistent between all objects. The schema master controls all updates and modifications to the schema.

• Domain Naming

When a new Domain is added to a forest the name must be unique within the forest. The Domain naming master must be available when adding or removing a Domain in a forest.

Domain Wide Roles:

• Relative ID (RID) Master

Allocates RIDs to DCs within a Domain. When an object such as a user, group or computer is created in AD it is given a SID. The SID consists of a Domain SID (which is the same for all SIDs created in the domain) and a RID which is unique to the Domain.

When moving objects between domains you must start the move on the DC which is the RID master of the domain that currently holds the object.

• PDC Emulator

The PDC emulator acts as a Windows NT PDC for backwards compatibility, it can process updates to a BDC.

It is also responsible for time synchronising within a domain.

It is also the password master (for want of a better term) for a domain. Any password change is replicated to the PDC emulator as soon as is practical. If a logon request fails due to a bad password the logon request is passed to the PDC emulator to check the password before rejecting the login request.

• Infrastructure Master

The infrastructure master is responsible for updating references from objects in its domain to objects in other domains. The global catalogue is used to compare data as it receives regular updates for all objects in all domains.

Any change to user-group references are updated by the infrastructure master. For example if you rename or move a group member and the member is in a different domain from the group the group will temporarily appear not to contain that member.

Important Note :

Unless there is only one DC in a domain the Infrastructure role should not be on the DC that is hosting the global catalogue. If they are on the same server the infrastructure master will not function, it will never find data that is out of date and so will never replicate changes to other DCs in a domain.

If all DCs in a domain also host a global catalogue then it does not matter which DC has the infrastructure master role as all DCs will be up to date due to the global catalogue.

Viewing and Transferring Roles

The roles can be viewed and transferred in the GUI or from the command line.

Gui View

Schema Master

To view the schema you must first register the schema master dll with Windows. To do this enter the following in the RUN dialog of the start menu.

regsvr32 schmmgmt.dll

Once you have done this the schema master mmc snap-in will be available.

Active Directory Domains and Trusts

The Domain naming master can be viewed and transferred from here.

Active Directory User and Computers

The RID, PDC emulator and Infrastructure master roles can be viewed and transferred from here.

NTDSUTIL

NTDSUTIL provides FSMO maintenance and the option to seize a role (covered in the FSMO Role Failure section below).

To transfer a role using ntdsutil use the example below as a template for all the roles.

• Open a command prompt
• Enter in ntdsutil
• At the ntdsutil command prompt enter in roles
• At the fsmo maintenance prompt enter in connection
• At the server connections prompt enter in connect to domancontrollername
• At the server connections prompt enter in quit
• At the fsmo maintenance prompt enter in transfer schema master
• Quit from the console

FSMO Role Failure

Some of the operations master roles are essential for AD functionality, others can be unavailable for a while before their absence will be noticed. Normally it is not the failure of the role, but rather the failure of the DC on which the role is running.

If a DC fails which is a role holder you can seize the role on another DC, but you should always try and transfer the role first.

Before seizing a role you need to asses the duration of the outage of the DC which is holding the role. If it is likely to be a short outage due to a temporary power or network issue then you would probably want to wait rather than seize the role.

Schema Master Failure

In most cases the loss of the schema master will not affect network users and only affect Admins if modifications to the schema are required. You should however only seize this role when the failure of the existing holder is considered permanent.

Note: A DC whose schema master role has been seized should never be brought back online

Domain Naming Master Failure

Temporary loss of this role holder will not be noticeable to network users. Domain Admins will only notice the loss if they try and add or remove a domain in the forest. You should however only seize this role when the failure of the existing holder is considered permanent.

Note: A DC whose schema master role has been seized should never be brought back online

RID Master Failure

Temporary loss of this role holder will not be noticeable to network users. Domain Admins will only notice the loss if a domain they are creating objects in runs out of relative IDS (RIDs). You should however only seize this role when the failure of the existing holder is considered permanent.

Note: A DC whose schema master role has been seized should never be brought back online

PDC Emulator Master Failure

Network users will notice the loss of the PDC emulator. If the DC with this role fails you may need to immediately seize this role. Only pre Windows 2000 clients and NT4 BDCs will be affected.

If you seize the role and return the original DC to the network you can transfer the role back.

Infrastructure Master Failure

Temporary loss of this role holder will not be noticeable to network users. Administrators will not notice the role loss unless they are or have recently moved or renamed large numbers of accounts.

If you are required to seize the role do not seize it to a DC which is a global catalogue server unless all DCs are global catalogue servers.

If you seize the role and return the original DC to the network you can transfer the role back.

Posted By : Graham Carmichael 4 Apr

PINE 64 next to a Raspberry PI 3