Starting from scratch with a new CentOS 7 Linode,
I found that iptables is set by default to block (although not reject)
packets to the IMAP and POP3 services.
Rackspace has a good primer
on setting up Dovecot that includes these instructions, but here's the
short answer:
sudo iptables -I INPUT 2 -p tcp --dport 587 -j ACCEPT sudo iptables -I
INPUT 3 -p tcp --dport 110 -j ACCEPT sudo iptables -I INPUT 4 -p tcp
--dport 143 -j ACCEPT sudo iptables -I INPUT 5 -p tcp --dport 993 -j
ACCEPT sudo iptables -I INPUT 6 -p tcp --dport 995 -j ACCEPT sudo
/etc/init.d/iptables save sudo /etc/init.d/iptables restart
That adds a rule to accept the IMAP and POP ports, both the regular and
SSL versions. Then we save the chain table and restart iptables. Now
you should be able to get in: $ telnet myhost.wlindley.com imap Trying
myhost.wlindley.com... Connected to myhost.wlindley.com. Escape
character is '^]'. * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR
LOGIN-REFERRALS ID ENABLE IDLE STARTTLS LOGINDISABLED] Dovecot ready.
Asterisk is an open-source telephone solution that runs over the
internet instead of running through copper lines. It offers a variety
of features such as voicemail and conference calling, much like
a land line telephone can.
For this guide we will install Asterisk from source rather than
from Ubuntu's repositories. The newer version offers several additional
features, including the ability to integrate a Google Voice account
as a trunk. We will use FreePBX as a web interface for our Asterisk
configuration.
Read the rest of the story on Linode's site
I used Debian 7.5 instead of Ubuntu. When I got to the section where it
said to:
apt-get install linux-virtual
I actually had to follow the instructions here
to get the local kernel matching the dahdi_dummy kernel module.
I also had to install the correct kernel source, from the hint here,
before the make commands would work:
apt-get install linux-headers-`uname -r`
The php5-suhosin package does not exist in the stable repository, so
I had to omit that from the php apt-get line.
By default, Debian has the Apache document root at /var/www; we want
to change that to /var/www/html. The VirtualHost directive is in file
/etc/apache2/sites-available/default − change the appropriate lines:
…
DocumentRoot /var/www/html
<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>
<Directory /var/www/html/>
…
To be able to install the Google Voice module, I had to:
# su - asterisk
$ cd /var/www/html/admin/modules/
$ mkdir _cache
Loaded Virtualmin onto a Linode running Centos 6. Ran into some
errors when trying to add a domain:
Failed to create virtual server : setquota: Cannot stat() mounted
device /dev/root: No such file or directory setquota: Mountpoint (or
device) / not found or has no quota enabled. setquota: Not all
specified mountpoints are using quota.
And indeed, from a root prompt:
# <strong>quotaon -p -a</strong>
quotaon: Cannot stat() mounted device /dev/root: No such file or directory
group quota on /home (/dev/xvdc) is off
user quota on /home (/dev/xvdc) is off
Hmm, yep, that's the same error. This thread on Virtualmin's forum
was a big clue, here's the first step to resolution:
# <strong>mount</strong>
...
/dev/xvda on / type ext3 (rw,noatime,grpquota,errors=remount-ro,usrquota)
...
Right, so our root / partition is indeed on /dev/xvda so we can
create the missing symbolic link:
# <strong>ln -s /dev/xvda /dev/root</strong>
# <strong>quotaon -a</strong>
quotaon: cannot find /home/aquota.group on /dev/xvdc [/home]
quotaon: cannot find /home/aquota.user on /dev/xvdc [/home]
#
Good, no error message. But things are still not working yet:
# <strong>quotaon /home</strong>
quotaon: cannot find /home/aquota.group on /dev/xvdc [/home]
quotaon: cannot find /home/aquota.user on /dev/xvdc [/home]
Before proceeding, in /etc/fstab please be sure "usrquota" and
"grpquota" are in the options line:
/dev/xvdc /home ext3 grpquota,errors=remount-ro,usrquota,grpquota,noatime,rw 0 1
Now, instead of going thru a dozen cryptic commands, go back to Webmin
(if Virtualmin is up, click Webmin on the top line). Open the System
tab and then Disk Quotas. You should see the /home partition listed,
and it probably says that quotas are not active. Simply hit "Enable
Quotas" and the display should change to:
*Filesystem *
*Type *
*Mounted From *
*Status *
*Action *
/home (users) /home (groups)
Linux Native Filesystem
Xen device C
User and Group Quotas Active
Disable Quotas
...Done!
Upon first install Virtualmin, you will need to set a few
configuration parameters:
- I recommend running Clam and SpamAssassin as servers, if you handle
email. If you delegate all email to a separate server, leave these
off.
We will be disabling root login to webmin / virtualmin. Start by
creating an administration group:
From the Virtualmin control panel, click at the top: Webmin
Open the webmin drop-down on the left
Click Webmin Users
Under Webmin Groups, click Create a new Webmin group
Call it "admins" or "devel" or as you wish. There is a Select All
link at the bottom of the list of permissions; use it.
Back on the Webmin User panel, click Convert Unix users to Webmin
users
Click in the radio-button for "Users with group" and put "wheel"
into the box (see previous post, where we set our administrator
users into the wheel group)
The default should be to use Unix authentication for the Webmin users.
That means, resetting your Unix password will update your Webmin login
as well.
Logout of Webmin and then back in with your username. Go back to Webmin
Users and click on the 'root' user in the list of users. Set the
password to "No password accepted" and voilá, your Webmin is now a
little more secure.
Disabling Unused Cronjobs
CentOS in particular puts unwanted tasks in the cron entries. They do
not appear in the 'crontab' proper but in /etc/cron.daily and
/etc/cron.hourly. Rename these files to be their hidden dotfile
equivalents:
cron.daily/.00webalizer
cron.daily/.freshclam
cron.daily/.makewhatis.cron
cron.hourly/.awstats
Otherwise, awstats will run every hour for every domain, regardless of
the settings you make in Virtualmin. Also I disabled 'makewhatis'
'webalizer' and 'freshclam' as I am not using them.
Ready to move your hosted websites to a new a Virtualmin
+ LAMP
(Linux/Apache/MySQL/Perl-PHP) server on a Linode?
Here's the steps to get everything working smoothly with a minimum of
hassle:
Initial Preparation
First, starting with a freshly provisioned CentOS install, ssh into the
root account. Let's see what we actually have for a distribution:
$ cat /etc/issue
CentOS Linux release 6.0 (Final)
Kernel r on an m
First, create regular user accounts for the administrators, and disable
direct root login. We will place these administrators into the 'wheel'
group so they can sudo, and also create a developer group:
# groupadd devel
# useradd -c "Winston Smith" -g devel --groups wheel -m -s /bin/bash wsmith
Use the visudo* *command to edit the /etc/sudoers file,
removing the leading # to un-comment this line:
## Allows people in group wheel to run all commands
%wheel ALL=(ALL) ALL
Now, set a password for yourself:
# passwd wsmith
The logout, and ssh back in as wsmith
If you haven't read the Linode Security Basics article,
now's a good time. At the very least, disable root logins by editing
the /etc/ssh/sshd_config file to modify the PermitRootLogin option
as follows:
PermitRootLogin no
Then restart ssh:
$ sudo service sshd restart
I also recommend fail2ban, which should reduce the clutter and risk of
repeated ssh attacks:
$ sudo yum install fail2ban
$ sudo chkconfig --level 23 fail2ban on
$ sudo service fail2ban start
Next, edit /etc/sysconfig/network and change the hostname. If there
is no HOSTNAME line, add one with your desired machine name in your
domain; it should look like:
HOSTNAME=linode1.example.com
That file is read at boot, so you might also want to set the hostname
for the current session:
`
$ sudo hostname linode1.example.com
`
Be sure that your DNS server has an A Record with that exact name,
pointing to your new server.
Install Updates before Virtualmin
Now we will update the base system --
`
$ sudo yum update
`
We haven't installed PHP and MySQL yet, but let's see what versions
will be installed from our currently selected repositories:
$ yum search php
Loaded plugins: fastestmirror
============================================ Matched: php ============================================
php.i686 : PHP scripting language for creating dynamic web sites
php-bcmath.i686 : A module for PHP applications for using the bcmath library
php-cli.i686 : Command-line interface for PHP
php-common.i686 : Common files for PHP
...
$ yum list php
Loaded plugins: fastestmirror
Available Packages
mysql.i686 5.1.52-1.el6_0.1 updates
php.i686 5.3.2-6.el6_0.1 updates
OK, well that's not the latest, but Centos assures us (as of
mid-October 2011) that Centos 6.1 will have updates. Meantime, the
folks at Centos recommend the use of the Continuous Release (CR)
repository, see this article.
$ sudo yum install centos-release-cr
$ sudo yum update
That installed, on my system, 144 new and updated packages. Now let's
see what that will do for us in terms of PHP and MySQL:
$ yum list php mysql
Loaded plugins: fastestmirror
...
Available Packages
mysql.i686 5.1.52-1.el6_0.1 updates
php.i686 5.3.3-3.el6 cr
Ah, a nice fresh version of PHP. Before going much further, I find it
convenient to also install the console version of emacs for editing,
and the 'screen' package for multi-virtual-screen remote
administration:
`
$ sudo yum install emacs-nox screen
`
Load Virtualmin
Download the install.sh script from http://www.virtualmin.com/download.html
into /usr/src ... and then execute it:
`
$ sudo bash # cd /usr/src # wget
http://software.virtualmin.com/gpl/scripts/install.sh
sh install.sh
`
That may take some time indeed! Eventually you should see:
INFO - Updating SpamAssassin rules...
INFO - Rule updates done
[root@linode1 src]#
Once it completes, login, as root, to your new virtualmin configuration
at your linode's address: https://linode1.example.com:10000 .. and then
read the next part of this article.
Useful Tools
sudo yum install emacs-nox screen
For PHP with Graphics support
sudo yum install gd php-gd ImageMagick ImageMagick-devel php-devel httpd-devel
sudo pecl install imagick
<em>(and, as root) </em>echo "extension=imagick.so" > /etc/php.d/imagick.ini
sudo apachectl graceful
The php-devel module is required for loading ImageMagick into PHP;
without it, you will get phpize: command not found. Note that the
pecl command above actually compiles some code, so you need the gcc
compilers and the various development modules.
Webmin and fail2ban
If you ever use Webmin to edit your firewall rules, you should be sure
to do this last step. It's also handy if you lock yourself out of your
secure shell, to be able to do a one-time reset of fail2ban's rules
from the webmin interface.
Login to Webmin. Under Networking, on the “Linux Firewall” main page,
click Module Config in the upper-left of the pane. On the configuration
page, in the “Configurable options” section, look for the line “Command
to run after applying configuration.” Click the button next to the text
box on that line, and in the text box enter service fail2ban restart
and then click the Save button at the bottom of the page. Now, whenever
you click “Apply Configuration” on the Firewall rule page, it will
automatically restart fail2ban.