Posts

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Setting up OS X Mail

Old hand Unix guys like myself are used to plain text email. OS X mail will gladly oblige me if I go to: Preferences –> Composing –> Message Format: { Plain Text }. But Apple chooses to use a proportionally spaced font: Helvetica by default. To fix this, go to: Preferences –> Fonts & Colors –> Use fixed width font for plain text messages. I think that these two should go hand in hand but Apple thinks otherwise.

Sadly, what you cannot fix is the line width. It would be nice to have the plain text message lines wrapped at the nth column but, I’ll take what I can get.

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Changing VMware Fusion network settings

For those that run VMware Fusion, the “/Library/Preferences/VMware Fusion”  directory on the Mac is a wealth of information.

$ cd /Library/Preferences/VMware\ Fusion/
$ ls -l
total 40
-r--r--r-- 1 root wheel 31 Nov 17 11:01 lastLocationUsed
-rw-r--r-- 1 root wheel 548 May 5 2018 license-fusion-100-e3-201704
-rw-r--r-- 1 root wheel 689 May 5 2018 license-fusion-100-e4-201704
-rw-r--r-- 1 root wheel 547 Dec 6 2013 license-fusion-50-e3-201202
-rw-r--r-- 1 root wheel 547 Apr 10 2014 license-fusion-60-e3-201303
-rw-r--r-- 1 root wheel 547 Oct 31 2014 license-fusion-70-e3-201404
-rw-r--r-- 1 root wheel 688 Oct 25 2014 license-fusion-70-e4-201404
-rw-r--r-- 1 root wheel 547 Jun 23 2016 license-fusion-80-e3-201505
-rw-r--r-- 1 root wheel 740 Nov 3 05:54 networking
-rw-r--r-- 1 root wheel 740 Aug 7 20:23 networking.bak.0
drwxr-xr-x 10 root wheel 340 Nov 17 11:01 thnuclnt
drwxr-xr-x 4 root wheel 136 Dec 6 2013 vmnet1
drwxr-xr-x 7 root wheel 238 Dec 6 2013 vmnet8
$

The license-fusion… files have your license keys as well as other information in them. But today, the jewel for me is the networking file:

$ cat networking
VERSION=1,0
answer VNET_1_DHCP yes
answer VNET_1_DHCP_CFG_HASH E08B... ...D0D8
answer VNET_1_HOSTONLY_NETMASK 255.255.255.0
answer VNET_1_HOSTONLY_SUBNET 172.a.b.0
answer VNET_1_VIRTUAL_ADAPTER yes
answer VNET_8_DHCP yes
answer VNET_8_DHCP_CFG_HASH 2031... ...F498
answer VNET_8_HOSTONLY_NETMASK 255.255.255.0
answer VNET_8_HOSTONLY_SUBNET 10.c.d.0
answer VNET_8_NAT yes
answer VNET_8_VIRTUAL_ADAPTER yes
...

This file defines the networks that your host-only and nat network adapters use. VMware appears smart enough to avoid network collisions e.g. using 192.168.1.0/255 for the NAT adapter at vmnet8 when that’s also the network configured on your home router.

According to this article (VMware login required), simply editing this file and restarting VMware Fusion’s networking component should change the dhcp setting that your machine uses. Any skilled system or network administrator should be able to get their hands around that.

Finally, the lines that specify DHCP hashes appear to be the mechanism that VMware uses to detect changes in the networking file. If you dig deeper, there’s a directory for vmnet1.

$ ls -l vmnet1
total 8
-rw-r--r--  1 root  wheel  1575 Nov 17 11:01 dhcpd.conf
-rw-r--r--  1 root  wheel  1575 Nov 17 11:01 dhcpd.conf.bak
$ cat vmnet1/dhcpd.conf
# Configuration file for ISC 2.0 vmnet-dhcpd operating on vmnet1.
#
# This file was automatically generated by the VMware configuration program.
# See Instructions below if you want to modify it.
#
# We set domain-name-servers to make some DHCP clients happy
# (dhclient as configured in SuSE, TurboLinux, etc.).
# We also supply a domain name to make pump (Red Hat 6.x) happy.
#

###### VMNET DHCP Configuration. Start of "DO NOT MODIFY SECTION" #####
# Modification Instructions: This section of the configuration file contains
# information generated by the configuration program. Do not modify this
# section.
# You are free to modify everything else. Also, this section must start
# on a new line
# This file will get backed up with a different name in the same directory
# if this section is edited and you try to configure DHCP again.

# Written at: 11/17/2018 11:01:21
allow unknown-clients;
default-lease-time 1800; # default is 30 minutes
max-lease-time 7200; # default is 2 hours

subnet 172.a.b.0 netmask 255.255.255.0 {
range 172.a.b.128 172.a.b.254;
option broadcast-address 172.a.b.255;
option domain-name-servers 172.a.b.1;
option domain-name localdomain;
default-lease-time 1800; # default is 30 minutes
max-lease-time 7200; # default is 2 hours
}
host vmnet1 {
hardware ethernet 00:50:56:x:y:z;
fixed-address 172.a.b.1;
option domain-name-servers 0.0.0.0;
option domain-name "";
}
####### VMNET DHCP Configuration. End of "DO NOT MODIFY SECTION" #######
$

 

This is just a standard dhcpd.conf file as you would see if you ran isc-dhcpd. The interesting thing is that the hash is what you get if you do this:
$ sed -ne '/VMNET DHCP.*Start/,/VMNET DHCP.*End/ p' vmnet1/dhcpd.conf | shasum
e08b... ...d0d8 -

The more you know…

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Testing python scripts

You have a python script that has some unit tests that you want to run:

python -c "m = __import__("my-script"); m.unittest()"

Runs the unittest() function within your script. N.B. this still works if your script has a hypen in the name which is my style.

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Mutt account passwords

First, to give credit where it’s due, I started here. That said, here’s how I store and access account passwords in mutt on Linux.

## -- Passwords: encrypted by gpg --------------------------------------------------------------

source “/bin/gpg -d ~/.keychain/mutt.password.neopost.gpg 2>/dev/null |”

The source line in gpg tells mutt to decrypt a file at startup. The file .keychain/mutt… contains two mutt configuration lines:

set imap_pass = "<my_email_password>"
set smtp_pass = "<my_email_password>"

I created it as follows:

$ cat <<EOF | gpg -r <my_gpg_id> ~/.keychain/mutt.password.neopost.gpg
set imap_pass = "<my_email_password>"
set smtp_pass = "<my_email_password>"
EOF
$

Gpg knows how to decrypt this file and retrieve the plain text configuration. Note well that I used a “Here” document to create the file. This keeps mail password out of the filesystem. Simple stuff, at mutt startup the first time I use it, gpg-agent asks for my gpg key and unlocks the configuration snippet.

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Of IPv6, and unhappy eyeballs

I’m a dinosaur. I still bring a little Soekris Net5501 configured as a NAT gateway with IPsec back home when on vacation. This solution works best in hotels that still offer Wired internet. I do this because:

  • Majorly, In many cases a hotel’s WiFi is a great example of the worst case engineering solution with wifi tuned just well enough that web browsing doesn’t suck but nothing else is considered.
  • Minorly, Hotel’s in the United States will probably be the last places on Earth to get IPv6.

The other advantages should be obvious. By bringing a router I can control or at least police my DNS.

My Soekris is tiny. It takes up about as much space as three tee shirts in my packed bag including an Ancient Apple Airport Express that can be tuned to run on 5GHz only. Off hand I want to mention that configuring 5GHz WiFi in each hotel room might bring the best improvement to WiFi overall but hoteliers can’t do this because lots of people have old devices that don’t do 5GHz or don’t do it well. No one wants to be the guy trying to explain to a customer that the problem isn’t the WiFi, it’s the customer’s 2007 vintage MacBook Pro that can’t use channel 149.

So, note my surprise when I find that things aren’t working better on my custom wifi, homed to the edge router over ethernet, during my latest hotel stay. What happened? I think this…

My router connects the internet and establishes a tuned IPSec tunnel back home. Once that works, it advertises IPv6 addresses from my /48 which route back to my house and then out to the internet. If the latency for all of that is 10ms no one would notice the difference. If it goes greater than 30ms things start getting funky. We’ve crossed into a time where if you have a dual stack machine, one with both IPv4 and IPv6, you’ll try to use IPv6 for outbound work first and revert to IPv4 only when v6 has too much latency. Well, folks, when you have just enough latency, this doesn’t look pretty.

No solution yet and possibly not ever. The problem with latency issues like this is that you can’t easily fix them. That’s why tuning latency out is so important. I’ll post more when I know more.

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Emacs use tabs rather than spaces.

Today, about the only place you should see an ascii TAB in a file is in a Makefile. In a world where memory is metered as gigabytes of RAM and terabytes of storage on fast SSDs there is absolutely no need to save space in a source code or configuration file by using a tab rather than two or four or eight spaces. Note well that I may be talking to your editor configuration and not you. But when you write code you should say what you mean and mean what you say unequivocally. I say this because I have been looking at a whitespace difference in my puppet checks for better than a month now. This is because my file has in production has tabs and my file in the puppet/git repository has spaces.

To that end, I’m linking this bit of Emacs magic for readers and my future self.

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Submission brutes

Brush aside vandals attacking my submission daemon with a little sed:


submission_brutes=$(bzcat /var/log/maillog.0.bz2 | \
cat - /var/log/maillog | \
sed -Ene '/postfix\/submission\/smtpd.*errors after AUTH/s/^.*[^0-9]+(([0-9]+\.){3}[0-9]*).*$/\1/p' | sort -u)
[[ ! -z "${submission_brutes}" ]] && pfctl -t blackhole -T add ${submission_brutes}