All posts by tomasz

Postfix DOS problem

Today suddenly my email server stopped accepting incoming connections. I wasn’t able to send any emails. After careful checking logs I have figured out that I’m a victim of DOS attack. More – I asked for it tuning maximum number of incoming connections in my firewall to low. Anyway, after correcting firewall I started to look over the internet how to better secure my Postfix configuration to prevent such problems in the future. What I have found is some simple main.cf tweaks posted on the nixCraft site:

disable_vrfy_command = yes
smtpd_delay_reject = yes
smtpd_helo_required = yes
smtpd_helo_restrictions = permit_mynetworks,
reject_non_fqdn_hostname,
reject_invalid_hostname,
permit

smtpd_recipient_restrictions =
permit_sasl_authenticated,
reject_invalid_hostname,
reject_non_fqdn_hostname,
reject_non_fqdn_sender,
reject_non_fqdn_recipient,
reject_unknown_sender_domain,
reject_unknown_recipient_domain,
permit_mynetworks,
reject_rbl_client list.dsbl.org,
reject_rbl_client sbl.spamhaus.org,
reject_rbl_client cbl.abuseat.org,
reject_rbl_client dul.dnsbl.sorbs.net,
permit

smtpd_error_sleep_time = 1s
smtpd_soft_error_limit = 10
smtpd_hard_error_limit = 20

Simple as that, and it works. Now I can see how my server is rejecting spammers one by one without even talking to them past HELO command.

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Replacing ignition distributor in Jeep’s 4.0L engines.

I know that’s for many Jeep owners it’s a piece of cake. Also it’s nothing you do every day. Probably most of you will never do it in theirs but it happened to me on Saturday – my engine started chirping. I looked and listened to the engine and (with help from the Jeep Forum guys) narrowed causes down to ignition distributor and/or oil pump. I decided to start with the distributor (lately if turned out to be good decision). Here is small how-to.

Removal

1. Tools

Tools

All you need is on the picture:

  • flat screwdriver
  • philips screwdriver
  • 13mm wrench
  • 19mm socket and ratchet
  • 8mm socket
  • Sharpie marker

After you have all tools we can start the job

2. Remove auxiliary electric fan

This step is only necessary when procedure is done on the Cherokee (XJ) model – this is the only way to turn the crankshaft vibration damper. In Grand Cherokee (ZJ) you have access to this bolt from underneath. Now disconnect the battery negative cable, then disconnect the radiator fan electric connector:

Auxiliary fan connector

Then unscrew (using 8mm socket) two bolts which are also mounting points for coolant reservoir pipe:

Fan bolts

And remove it simply pulling it up.

3. Remove distributor cap

But before you do this there are two things to be done. First – write down somewhere numbers to which cylinder which wire goes. Unfortunately there is no such info on any distributor caps I have seen. You can also print this picture:

Cables order

Then make a mark both on the distributor and the cap just next to the cylinder number one terminal:

Make mark

Now, using philips screwdriver, unbolt and remove distributor cap.

4. Set crankshaft in correct position

Now lie under the car and turning the crankshaft vibration dumper clockwise (!) find the notch on it and mark it with sharpie – it will make our job a little easier:

Mark dumper

Then, this time from the top, rotate it clockwise until that notch will be aligned with 0 degree mark:

Set to zero

Now the rotor should be aligned with the mark we did before:

Rotor aligned with the mark

5. Remove the distributor

Now take out the rotor. Then disconnect distributor’s connector

Disconnect distributor

Now using 13mm wrench unbolt distributor from engine block:

Unbolt distributor

and pull it out from the engine.

Installation

6. Set oil pump

Before inserting new distributor in it’s place you need to make some alignment. First, using flat screwdriver, set the oil pump shaft around 11 o’clock position:

Set oil pump

7. New distributor preparation

Then take the new distributor, put the old cap on it and mark the distributor next to the number one cylinder terminal as you did with the old one.

Transfer mark

Then set distributor’s shaft in a way that rotor’s line should point on 4 o’clock.

Set distributor shaft

8. Insert new distributor

Remembering about distributor gasket insert new distributor carefully into the engine’s block keeping distributor’s hold down ear aligned with bolt hole in the engine. During the insertion process the distributor shaft should rotate a little bit. At the and it should point exactly at the mark we made before.

New distributor in place

If it points in other direction you have to pull it out again and change the initial position to achieve the final one. Then bolt it down to the engine’s block.

9. Rotor, cap, connections

Now install the rotor, then the cap and distributor connector. Then using previously made notes correctly connect all ignition cables.

10. Fan

Reinstall the auxiliary fan and connect negative battery cable. Start engine. Take a beer.

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HVAC disaster

We finally moved in to our new house. After couple of days spent on cleaning, unpacking and making ourselves comfortable we figured out one thing – the HVAC system is just a disaster.

First – the thermostat is in the worst place in the house. Simply first test shows that while the thermostats shows 1 degree differences, the actual temperature it that room floats more than 2 degrees in each direction.

Second – all registers are broken – none of them shuts completely and none of them works smooth

Third – the A/C unit and fan are probably undersized (I still have to make measurements) – it needs to work for more than 1h to cool down the room by 1 degree.

A lot of work is waiting but it only makes me more motivated to quickly finish that project.

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