Installation

To install we need to run the following command:

sudo apt-get install -y sks

Now we build the key database:

sudo sks build

And change the permissions for the sks user:

sudo chown -R debian-sks:debian-sks /var/lib/sks/DB

Next we need to make sks start from init, open up /etc/default/sks in your favourite editor and *initstart* to look like below:

initstart=yes

Now we can start the service with:

sudo /etc/init.d/sks start

Your keyserver will now be up and running on port 11371.

Web interface

We’ll need to create a web folder within sks with the following command:

sudo mkdir -p /var/lib/sks/www/

Change it’s permissions so the sks user can access it.

sudo chown -R debian-sks:debian-sks /var/lib/sks/www

And finally we need create a single HTML file for the interface, I have provided that …

Installation

First up we’ll need to install git and some Python tools to get Gitosis installed.

sudo apt-get install -y git-core gitweb python-setuptools

Next we have to clone gitosis from it’s git repository and install it.

cd /tmp
git clone git://eagain.net/gitosis.git
cd gitosis
sudo python setup.py install

Adding your git user

sudo adduser --system --shell /bin/sh --gecos 'git version control' --group --disabled-password --home /home/git git

The above command creates a new system user with /bin/sh as it’s shell with no password and a homedir of /home/git/ and also creates a group with the same name.

Initialising gitosis

You’ll need an SSH key for this, if you have one simply copy the contents of it to your new git server, if you do not have one then you can generate one on your machine using

ssh-keygen

And then …

*I would generally not advise using this unless you have skill at debugging why OOM has spawned and also debugging kernel panics after they happen, from logs.*

It is possible to configure your kernel to panic when OOM is spawned, which in itself is not useful but, coupled with a kernel option for auto-rebooting a system when the kernel panics it can be a very useful tool.

Think before implementing this and use at your own risk, I take zero responsibility for you using this.

sudo sysctl vm.panic_on_oom=1
sudo sysctl kernel.panic=X # X is the amount of seconds to wait before rebooting

*DO NOT FORGET TO CHANGE X*

This will inject the changes in to a system that is currently running but will be forgotten on reboot so use the lines below to save permanently.

sudo echo "vm.panic_on_oom=1" >> /etc/sysctl.conf
sudo echo "kernel.panic …

Preparation

First we need to make sure we have all the stuff we need to compile mk livestatus and run it

sudo apt-get install make build-essential xinetd ucspi-unix

MK Livestatus

Grab the mk livestatus source from here, currently it’s version 1.1.10p3 but update the commands below to match your version.

wget http://mathias-kettner.de/download/mk-livestatus-1.1.10p3.tar.gz
tar xvzf mk-livestatus-1.1.10p3.tar.gz
cd mk-livestatus-1.1.10p3
./configure
make
sudo make install

Xinetd

Now that it’s compiled we need to write a xinetd config for it, create a new file called /etc/xinetd.d/livestatus and put the following in it

service livestatus {
    type = UNLISTED
    port = 6557
    socket_type = stream
    protocol = tcp
    wait = no
    cps = 100 3
    instances = 500
    per_source = 250
    flags = NODELAY
    user = nagios
    server = /usr/bin/unixcat
    server_args = /var/lib/nagios3/rw/live
    only_from = 127.0.0.1 # modify this to …

The point

The whole point of this is to get as much load off of Apache as possible to keep the server running nice and smoothly.

Configuration

The configuration below will mean that nginx will serve basically everything;

  • static files
  • uploaded files and
  • cached content

simply replace the VARIABLES below and everything should be good to go, if copy-pasting from below isn’t working properly you can download a full copy from here.

server {
  listen 80;
  server_name **DOMAIN_HERE**;
  access_log /var/log/nginx/access.**DOMAIN_HERE**.log;

  gzip on;
  gzip_disable msie6; # disable gzip for IE6
  gzip_static on;
  gzip_comp_level 9; # highest level of compression
  gzip_proxied any;
  gzip_types text/plain text/css application/x-javascript text/xml application/xml application/xml+rss text/javascript;

  proxy_redirect off;
  proxy_set_header Host $host;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_pass_header Set-Cookie;root **/PATH/TO/WORDPRESS**;

  # default location, used for the basic proxying
  location / {
    # if we're requesting a file and …

Pound is a great little load balancer, it’s fast, opensource and supports SSL termination, which is great!

Install

sudo apt-get install pound

Configuration

The default configuration should be pretty good for most purposes, but feel free to tweak as you require.

HTTP

We’ll first look at load balancing HTTP, in case you don’t want or need HTTPS load balancing.

We’ll need delete all the content within ListenHTTP block, once done it should look like this

ListenHTTP
End

Now we add an address and port to listen on and finally a line to remove an HTTP header

ListenHTTP
    Address 0.0.0.0 # all interfaces
    Port 80
    HeadRemove "X-Forwarded-For"
End

This is a basic configuration, for each backend we want to load balance we’ll need to add a service within that listener.

You’ll notice we’re removing incoming headers called X-Forwarded-For, this is to make …

A simple yet effective method for protecting your mail server from spam is to use greylisting. In simple terms, when an email is received the server will temporarily reject it with a 450 response code claiming that the server is busy, the sending server should then attempt to try to deliver at a later point in time, if enough time has passed the recipient server will then accept the incoming mail and whitelist the send address for a period of time.

This is effective because most spam servers are configured not to retry the send whereas real mail servers generally will retry. This sadly does not protect against spam coming from comprised mail servers or accounts like on Hotmail.com.

Installation

sudo apt-get install postgrey

Configuring Postgrey

By default Postgrey runs on 127.0.0.1:60000, which is the local loopback interface so it is not exposed to the …

This really should be quite a quick and simple post.

I use several tools to protect my mail servers from spam, the most effective of these I’ve found is using external lists in conjunction with reject_rbl_client and reject_rhsbl_client.

+======================+======================================================================================================+ | Service | description | +======================+======================================================================================================+ | zen.spamhaus.org | A single lookup for querying the SBL, XBL and PBL databases. | | | - SBL - Verified sources of spam, including spammers and their support services | | | - XBL - Illegal third-party exploits (e.g. open proxies and Trojan Horses) | | | - PBL - Static, dial-up & DHCP IP address space that is not meant to be initiating SMTP connections | +———————————+———————————————————————————————————————————————————+ | dnsbl.sorbs.net | Unsolicited bulk/commercial email senders | +———————————+———————————————————————————————————————————————————+ | spam.dnsbl.sorbs.net | Hosts that have allegedly sent spam to the admins of SORBS at any time | +———————————+———————————————————————————————————————————————————+ | b1.spamcop.net | IP addresses which have been used to transmit reported email to SpamCop users | +———————————+———————————————————————————————————————————————————+ | rhsbl.ahbl.org | Domains sending spam, domains owned by spammers, comment spam domains, spammed URLs …

This is part 4 of my series on configuring a mail server, please see part one, part two and part three if you’re not familiar with them.

The content of this article was written to work with the previous three articles but should work on any SpamAssassin set-up.

Razor

First off we need to install Razor.

sudo apt-get install razor

Now we need to run three commands to register and configure Razor.

sudo razor-admin -home=/etc/spamassassin/.razor -register
sudo razor-admin -home=/etc/spamassassin/.razor -create
sudo razor-admin -home=/etc/spamassassin/.razor -discover

These 3 commands should be pretty self explanatory, they register Razor, create it’s configuration and discover the Razor servers.

Pyzor

Now we’ll install Pyzor.

sudo apt-get install pyzor

Now we also need to tell Pyzor to discover it’s servers.

pyzor --homedir /etc/mail/spamassassin discover

SpamAssassin

Add the following lines to the end …

I have created a scripts that handle these tasks for you, available `here`_.

First thing we need to do is create an sources list specifically for security.

sudo grep "-security" /etc/apt/sources.list | sudo grep -v "#" > /etc/apt/security.sources.list

Now that this is done we can simply continue to use the command below to trigger security-only upgrades

sudo apt-get upgrade -o Dir::Etc::SourceList=/etc/apt/security.sources.list

Note

This will work until you upgrade your distro (e.g. 10.04 -> 12.04), at which point you will need to re-run the first command to regenerate the security.sources.list file.

This is part 3 of my guide to getting a mail server configured with all the sexy bits to improve deliverability, spam and virus protection.

You can view part 1 here and part 2 here.

The key pair

We need to create a key pair to sign emails with:

.. code-block:: bash
openssl genrsa -out private.key 1024 openssl rsa -in private.key -out public.key -pubout -outform PEM sudo mkdir /etc/dk/ sudo cp private.key /etc/dk/dk.key

Now we can move on to DK and DKIM signing, make sure you keep the public key for later.

DKIM

First we’ll need to install an application to sign our emails.

sudo apt-get install dkim-filter

Once installed we need to configure it, open up /etc/default/dkim-filter, modify the file to look like below replacing <DOMAIN> with the domain you want to sign email from.

DAEMON_OPTS="-l -o X-DomainKeys …

This is part 2 of my series on mail servers on Debian 6/Ubuntu 10.04, it should work on other versions of each though. Part 1 is available here.

SpamAssassin

First off we’ll get SpamAssassin installed and configured.

sudo apt-get install spamassassin

We’ll be configuring SpamAssassin as a daemon that Postfix interfaces with using spamc.

SpamAssassin on Debian and Ubuntu runs as root which is NOT a good thing so we’ll need to make some changes.

We’ll add a group called spamd with GID**5001**.

sudo groupadd -g 5001 spamd

Next we add a user spamd with UID 5001 and add it to the spamd group, as well as set it’s home directory as /var/lib/spamassassin and make sure it has no shell access or SSH access.

sudo useradd -u 5001 -g spamd -s /usr/sbin/nologin -d /var/lib/spamassassin spamd

Now …

This guide is part 1 of what I plan will be a couple of guides that take you through installing a base mail system, SpamAssassin, DKIM and much more. Stay tuned.

This guide was written for Debian 6 but should be the same or similar for Debian 5 and Ubuntu 10.04 and above.

The installation

sudo apt-get install dovecot-imapd postfix sasl2-bin libsasl2-2 libsasl2-modules

Choose “Internet site” when prompted and enter the fully qualified name of your server.

Once all this is done installing we’ll need to make some changes, first off will be Postfix.

Postfix

Open up /etc/postfix/main.cf and add the following to the end of the file

home_mailbox = Maildir/
smtpd_sasl_auth_enable = yes
smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $myhostname
broken_sasl_auth_clients = yes

smtpd_sender_restrictions = permit_sasl_authenticated,
    permit_mynetworks,

smtpd_recipient_restrictions = permit_mynetworks,
    permit_sasl_authenticated,
    reject_unauth_destination,
    reject_unknown_sender_domain,

Here we basically tell Postfix to store all email in maildir format in the user’s home directory. We …

Recently I started using Pound as a load balancer to a cluster of nginx servers and found my access logs were filled with the IP address of the load balancer. I did some digging and found the correct way to “fix” this.

First thing you need to do is make sure you remove X-Forwarded-For from Pound

ListenHTTP
    # ... snip ...
    # ... snip ...
    HeadRemove "X-Forwarded-For"
End

Once this is done, reload Pound.

Next you need nginx compiled with realip module - http://wiki.nginx.org/NginxHttpRealIpModule

On Ubuntu/Debian servers this module comes by default, otherwise you may have to compile it in yourself using the following option:

--with-http_realip_module

Once this is all done modify your nginx vhosts and add the following 2 lines

set_real_ip_from [IP];
real_ip_header X-Forwarded-For;

Where [IP] is the IP address of your load balancer.

To configure this to work with Apache you need the mod_rpaf module.

I’d first like to point out that although the VMDKs are shared between hosts using a shared SCSI BUS they are not synched, meaning that if you write to the mounted point on any machine it will not display on other machines with the same mount point until you remount the drive. Annoying, but understandable.

To business.

First off all machines that you want to share this VMDK with will need to be OFFLINE.

Next up we create the VMDK, I find it easiest to do this by adding hardware to an already existing machine, I’m going to use one that I want the VMDK shared with to make it even simpler.

Create a new disk

You will need to enable clustering features as shown below, this means you cannot use thin provisioning.

Choose disk size

You will need to add the VMDK to a new SCSI BUS, this will usually begin with 1: or …

I was recently tasked with adding Google tracking cookies to our nginx logging for a couple of sites. It was so it could be pushed through a log processor.

It turned out too be a little trickier than it would have been with Apache, but the process itself is still quite simple.

Open up the server definition you wish to add it to and add a custom log format like below

log_format g-a '$remote_addr - $remote_user [$time_local] ' '"$request" $status $body_bytes_sent ' '"$http_referer" "$http_user_agent" ' '"__utma=$cookie___utma;__utmb=$cookie___utmb;__utmc=$cookie___utmc;__utmv=$cookie___utmv;__utmz=$cookie_umtz"';

This log format can then be added to your access log like below:

access_log /var/log/nginx/access.example.com.log g-a;

Reload nginx

sudo /etc/init.d/nginx reload

If all goes well, you should see Google Analytics appearing in your access logs like below

1.1.1.1 - - [05/Jun/2011:20:35:50 +0100] "GET / HTTP …

Quite a simple one:

ssh -f USER@INTERMEDIATE_DEVICE -L LOCAL_PORT:DESTINATION_DEVICE:DESTINATION_PORT -N

-f tells ssh to go to background -L binds a local port to a remote device and port -N tells ssh not to execute any commands

So use this to tunnel from local port 8000 in to a remote machine on port 22 you’d use

ssh -f user@server.test.com -L 8000:server.destination.com:22 -N

Once the tunnel is open you can use the following to ssh or scp data around

ssh localhost -p 8000
scp -P 8000 /path/to/local/file user@localhost:~
scp -P 8000 user@localhost:/path/to/remote/file .

I use ssh tunnels all the time to remote access and use one of our Solr servers that is blocked behind a firewall.