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Latest Posts
- Black background in all desktops after Ubuntu 13.10 upgrade Posted on October 27, 2013
- Monitoring TFTPd server Posted on September 18, 2013
- Chef encountered an error attempting to create the client Posted on September 16, 2013
- Can't locate local/lib.pm CPAN error on Ubuntu 12.04 Posted on September 10, 2013
- Reverse DNS in BIND 9.8 Posted on September 4, 2013
October 27, 2013
Black background in all desktops after Ubuntu 13.10 upgrade
by Alpha01
So I just upgraded my Dell XPS 13 laptop from Ubuntu 13.04 to 13.10, and immediately the first thing I noticed that all of my desktops had a black background. and manually changing the background wallpaper took no effect. Turns out this is a common problem. In my case it turned out to be related to Gnome, which I found it to be rather interesting giving that a Gnome specific setting will cause this problem in Unity.
Fix
gsettings set org.gnome.settings-daemon.plugins.background active true
Resources
Tags: [ubuntu September 18, 2013
Monitoring TFTPd server
by Alpha01
So I just spent the last two hours of my life trying to figure why PXE booting was not working in my home network. Turned out the root cause was my fault completely since, I forgot to add a firewall rule on my dhcp/PXE server to allow incoming UDP connections on port 69.
Fix
iptables -A INPUT -p udp -m udp --dport 69 -j ACCEPT
As with just about any other service, this service can be monitored using Nagios. Originally, I had problems using the check_tftp.pl and check_tftp plugins that are available from on Nagios Exchange repo, mainly because of the way I have setup my machines.
-
check_tftp- This plugin was useless in my environment because this plugin all it does, is send out an status command to the TFTP server. Since I’m using the BSD tftp client, all status commands sent to any host will always show up as being connected regardless. http://exchange.nagios.org/directory/Plugins/Network-Protocols/TFTP/check_tftp/details -
check_tftp.pl- This plugin was not opted to work in my environment. Mainly because it usesNet::TFTP, unlike the tftp client application,Net::TFTPdoes not support specifying a custom reverse connection port (or port ranges). By default, when connecting to a TFTP server, the TFTP server will dynamically choose a random non-standard port to connect back to the client machine and proceed with the TFTP download. My Nagios machine (like all of my machines) are set to drop all incoming packets except for specific ports and related/established connections. http://exchange.nagios.org/directory/Plugins/Network-Protocols/TFTP/check_tftp-2Epl/details
This lead me to the path of writing my own custom solutions. So I wrote a simple Nagios plugin that monitors TFTP. All it simply does, is download a non-empty file called test.txt.
#!/usr/bin/perl -w
# Tony Baltazar. root[@]rubyninja.org
use strict;
use Getopt::Long;
my %options;
GetOptions(\%options, "host|H:s", "port|p:i", "rport|R:s", "file|f:s", "help");
if ($options{help}) {
usage();
exit 0;
} elsif ($options{host} && $options{port} && $options{file}) {
chdir('/tmp');
my $cmd_str = ( $options{rport} ? "/usr/bin/tftp -R $options{rport}:$options{rport} $options{host} $options{port} -c get $options{file}" : "/usr/bin/tftp $options{host} $options{port} -c get $options{file}");
my $cmd = `$cmd_str`;
if ($? != 0) {
print "CRITICAL: $cmd";
system("rm -f /tmp/$options{file}");
exit 2;
} else {
if (! -z "/tmp/$options{file}" ) {
print "TFTP is ok.\n$cmd";
system("rm -f /tmp/$options{file}");
exit 0;
} else {
print "WARNING: $cmd";
system("rm -f /tmp/$options{file}");
exit 1;
}
}
} else {
usage();
}
sub usage {
print <<EOF;
$0: TFTP monitor check Nagios plugin.
Syntax: $0 [--help|-H=<TFTP server> --port=<TFTP Port> --file=<Test file>]
--host | -H : TFTP server.
--port | -p : TFTP Port.
--file | -m : Test file that will be downloaded.
--help | -h : This help message.
Optionally,
--rport | -R : Explicitly force the reverse originating connection's port.
EOF
}
Seeing the plugin in action
Assuming, we’re using port udp 1069 to allow the TFTP server (192.168.1.2) to connect to the Nagios monitoring machine.
[root@monitor libexec]# iptables -L -n |grep "Chain INPUT"
Chain INPUT (policy DROP)
[root@monitor libexec]# iptables-save|grep 1069
-A INPUT -s 192.168.1.2/32 -p udp -m udp --dport 1069 -j ACCEPT
Firewall not allowing TFTP to connect back using port 1066.
[root@monitor libexec]# su - nagios -c '/usr/local/nagios/libexec/check_tftp.pl -H 192.168.1.2 -p 69 -R 1066 -f test.txt'
CRITICAL: Transfer timed out.
Downloading a non-existing file from the TFTP server.
[root@monitor tmp]# su - nagios -c '/usr/local/nagios/libexec/check_tftp.pl -H 192.168.1.2 -p 69 -R 1069 -f test.txtFAKESHIT'
WARNING: Error code 1: File not found
Successful connection and transfer.
[root@monitor tmp]# su - nagios -c '/usr/local/nagios/libexec/check_tftp.pl -H 192.168.1.2 -p 69 -R 1069 -f test.txt'
TFTP is ok.
perl nagios networking September 16, 2013
Chef encountered an error attempting to create the client
by Alpha01
So I’m finally starting to keep up with modern times and started to learn Chef more in depth. My goal is to completely automate and easily manage all of virtual machine instances running in my home network.
Upon attempting to bootstrap my very first node, I received the following error:
ubuntu Creating a new client identity for ubuntu01 using the validator key.
ubuntu
ubuntu ===================================================================
ubuntu Chef encountered an error attempting to create the client "ubuntu01"
ubuntu ===================================================================
ubuntu
ubuntu
ubuntu Resource Not Found:
ubuntu -------------------
ubuntu The server returned a HTTP 404. This usually indicates that your chef_server_url is incorrect.
ubuntu
ubuntu
ubuntu
ubuntu Relevant Config Settings:
ubuntu -------------------------
ubuntu chef_server_url "https://chef.rubyninja.org:443"
ubuntu
ubuntu
ubuntu
ubuntu [2013-09-15T22:25:28-07:00] FATAL: Stacktrace dumped to /var/chef/cache/chef-stacktrace.out
ubuntu Chef Client failed. 0 resources updated
ubuntu [2013-09-15T22:25:28-07:00] FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)
This essentially means that the node is not able to communicate with the Chef server. In my case, it turned out that the ubuntu01 machine was not using my local DNS servers, thus the chef.rubyninja.org lookup from the machine was failing.
ubuntu chef September 10, 2013
Can't locate local/lib.pm CPAN error on Ubuntu 12.04
by Alpha01
So the default Perl installation that ships with Ubuntu 12.04 LTS, does not include local::lib which is necessary if you want to use CPAN.
Error
Can't locate local/lib.pm in @INC (@INC contains: /home/tony/perl5/lib/perl5 /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl /home/tony) at /usr/share/perl/5.14/CPAN/FirstTime.pm line 1300.
Fix
sudo apt-get install liblocal-lib-perl
Resources
Tags: [perl ubuntu September 4, 2013
Reverse DNS in BIND 9.8
by Alpha01
I use BIND on my home network, and giving the bast amount of virtual machines I have online, I’ve always find myself wanting to easily look up which machine is using which IP address without having to ssh into the actual vm or check the zone file. Configuring reverse DNS in BIND 9.8 is actually a dead simple process.
First, a separate zone file for PTR records needs to be created, I named mine db.192.168.1.255.
Note: since my network address space is 192.168.1, the actual PTR record will be the network address backgrounds followed by in-addr.arpa..
$TTL 3h
@ IN SOA ns1.rubyninja.org. dnsadmin.rubysecurity.org. (
2013090701 ; serial
3h ; refresh after 3 hours
1h ; retry after 1 hour
1w ; expire after 1 week
1H ) ; negative caching TTL of 1 hour
IN NS ns1.rubyninja.org.
IN NS ns2.rubyninja.org.
14.1.168.192.in-addr.arpa. IN PTR email.rubyninja.org.
Lastly, the zone entry needs to be added to the master named.conf file. Mine looks like this
zone "1.168.192.in-addr.arpa" IN {
type master;
file "etc/zones/db.192.168.1.255";
allow-query { any; };
};
After reloading Bind, you verify reverse DNS works by using the utility of your choice; ie dig, host, nslookup, etc..
nslookup 192.168.1.14
Server: 192.168.1.10
Address: 192.168.1.10#53
14.1.168.192.in-addr.arpa name = email.rubyninja.org.
bind