Tuesday 10 September 2019

Locking down ISAKMP / IPSec (UDP 500 , 4500 and IP 50) on the ASA 5500 Series

By default when enabling ISAKMP / IPSec on an interface the ASA permits access to the service (UDP 500, 4500 and IPSec) to everyone. However in some circumstances where you can reliably predict the source of VPN initiaitors you should ideally lock down access. Unfortuantely this can't be performed via apply an ACL to the interface and instead needs to be performed via the control pane.

We'll firstly need to obtain a list of the IP's in tunnel groups and add them to an ACL e.g.:

access-list outside-control-plane extended permit udp host <REMOTE PEER #1> host <ASA-VPN-ENABLED-INTERFACE> eq 500
access-list outside-control-plane extended permit udp host <REMOTE PEER #2> host <ASA-VPN-ENABLED-INTERFACE> eq 500
access-list outside-control-plane extended deny udp any any eq 500

access-list outside-control-plane extended permit udp host <REMOTE PEER #1> host <ASA-VPN-ENABLED-INTERFACE> eq 4500
access-list outside-control-plane extended permit udp host <REMOTE PEER #2> host <ASA-VPN-ENABLED-INTERFACE> eq 4500
access-list outside-control-plane extended deny udp any any eq 4500

access-list outside-control-plane extended permit ipsec host <REMOTE PEER #1> host <ASA-VPN-ENABLED-INTERFACE>
access-list outside-control-plane extended permit ipsec host <REMOTE PEER #2> host <ASA-VPN-ENABLED-INTERFACE>
access-list outside-control-plane extended deny ipsec any any

access-group outside-control-plane in interface outside-pri control-plane

Note: The above examples presume you do NOT have any IPSec VPN servers behind the firewall.

We can also perform the same for SSL VPNs:

access-list outside-control-plane extended permit tcp host <REMOTE PEER #1> host <ASA-VPN-ENABLED-INTERFACE> eq 443
access-list outside-control-plane extended permit tcp host <REMOTE PEER #2> host <ASA-VPN-ENABLED-INTERFACE> eq 443
access-list outside-control-plane extended deny tcp any <ASA-VPN-ENABLED-INTERFACE> eq 443

Thursday 8 August 2019

Setting up bonding with LACP using the ip command in Linux

This can be accomplished quite quickly with the IP command if you only need it temporarily:

ip link add bond0 type bond
ip link set bond0 down
ip link set bond0 type bond mode 802.3ad
ip link set enp1s0 down
ip link set enp1s0 master bond0
ip link set enp2s0 down
ip link set enp2s0 master bond0
ip link set bond0 up

and to remove the bonding we can issue:

ip link del bond0
ip link set enp1s0 up
ip link set enp2s0 up

Quickstart: Installing Arch Linux 2019.X

Firstly download the latest iso image from one of the mirrors below:

wget https://www.mirrorservice.org/sites/ftp.archlinux.org/iso/2019.08.01/archlinux-xxxx.xx.xx-x86_64.iso
and then write it to your preferred media:
dd bs=8M if=archlinux-xxxx.xx.xx-x86_64.iso of=/dev/sdX | sync
Upon booting the image select the default selection to boot Arch.

This will get you into the system under the root user.

The setup portion is a Gentoo style approach of efffectively 'assembling' the system yourself.

From here we'll firstly partition the disks:
sdX               8:0    0 1000G  0 disk 

In this example we'll create three partitions - one for the root fs, another for our home fs and finally one for swap.
parted -a optimal /dev/sdXhyu
mktable gpt
mkpart ESP boot fat32 0% 500MB
mkpart root ext4 500MB 250000MB
mkpart home ext4 250GB 750GB
mkpart swap ext4 750GB 800GB
set 1 boot on
Create the filesystems with:
mkfs.msdos /dev/sdX1
mkfs.ext4 /dev/sdX2
mkfs.ext4 /dev/sdX3
mkfs.ext4 /dev/sdX4
mkswap /dev/sdX4
swapon /dev/sdX4
Proceed by mounting the file systems:
mount -t auto /dev/sdX2 /mnt
mkdir -P /mnt/boot/EFI && mount -t auto /dev/SdX1 /mnt/boot/EFI
mkdir /mnt/home && mount -t auto /dev/SdX3 /mnt/home
We'll need the network setup at this point so we can access the arch repo's:
and then pull down all the nessasery compontents for the root fs:
pacstrap /mnt base base-devel
Once complete we'll need to generate the fstab for the new system:
genfstab -U /mnt >> /mnt/etc/fstab
and then change our root password by chrooting into the new system along with the hostname:
arch-chroot /mnt
hostname arch-box
We'll also configure regional and time settings with:
ln -sf /usr/share/zoneinfo/<region>/<city> /etc/localtime
hwclock --systohc
printf "LANG=en_GB.UTF-8" > /etc/locale.conf
export LANG=en_GB.UTF-8
I'm going to use KDE Plasma for the desktop environment:
pacman -S xorg xorg-server xorg-xinit plasma-meta sddm
Finally we will configure grub:
pacman -S grub efibootmgr dosfstools os-prober mtools
grub-install --target=x86_64-efi --efi-directory=/boot/EFI --bootloader-id=grub_uefi --recheck
grub-mkconfig -o /boot/grub/grub.cfg
Exit the jail:
and restart:
shutdown -r now
Once booted into the new OS we'll setup the network configuration - for this example I'll be setting up DHCP.

With Arch we have a few options for network configuration - either netctl or networkd (a newer component.)
vi /etc/netctl/enp2s0
Description=LAN interface
Ensure the interface will come up on boot by issuing:
netctl enable enp2s0
Enable and start the DHCP service with:
systemctl enable dhcpcd
systemctl start dhcpcd
and then attempt to start the interface with:
netctl start enp2s0

Friday 12 July 2019

Using Juniper SRX devices as routers

The SRX series are part of Junipers security line of products and provide firewall among a host of other security features such as IDS and IPS.

However you can effectively use the SRX range as a traditional router by changing the forwarding mode from flow based (stateful inspected) to packet based (stateless per packet inspection.)

You can verify the forwarding mode by issuing:

show security flow status

We should firstly ensure we remove any existing security configuration from the device with:

delete security

and then ensure the forwarding mode is set to 'packet based':

set security forwarding-options family mpls mode packet-based

commit it and then reboot:

run request system reboot

Upon restart check the forwarding mode again with:

show security flow status

Thursday 4 July 2019

Configuring an Etherchannel (with LACP) between JunOS and Cisco IOS

Juniper JunOS

Firstly create the aggregated interface:

edit chassis
set aggregated-devices ethernet device-count 2

edit interfaces
set ae0 aggregated-ether-options

and define the LACP interval period (i.e. the rate at which the device will send / receive LACP protocol messages):

set aex aggregated-ether-options lacp periodic fast

By default the 'lacp periodic fast' sets the transmission rate to 1 second.

Note: It's important that the rate is matched on the other end as well.

We'll now associate our interfaces with the aggregated link we've just configured:

edit interfaces
edit ge-0/0/1
set ether-options 802.3ad ae0
edit ge-0/0/2
set ether-options 802.3ad ae0

Cisco IOS

conf t
int range gi1/0/1-2
channel-protocol lacp
channel-group 1 mode active
lacp rate fast
no shut

int po1
description etherchannel

Tuesday 2 July 2019

Base Junos Configuration

The following template will get the fundamental features setup in Junos and act as a base for building more advanced configurations:

# Enter configuration mode
configure exclusive

# Configure root user key / password
set system root-authentication load-key-file
set system root-authentication plain-text-password

# Enable remote management
edit system services
active ssh
ativate web-management https
set web-management https port 443
set web-management https system-generated-certificate
set web-management https interface fxp0.0

# Disable insecure services
deactivate telnet
decativate web-management http

# Setup hostname
set system host-name "host01"

# Setup time / date / ntp
set system time-zone Europe/London
set date ntp 1.uk.pool.ntp.org
set cli idle-timeout 10

# Setup new user and assign login class
edit system login
edit user jbloggs
set authentication plain-text-password
set full-name "Joe Bloggs"
set class operator | read-only | super-user

# Create custom login class
set system login class test-class permissions [interface interface-control]
set system login class test-class idle-timeout 10
# Configure RADIUS
set system radius-server source-address
edit system radius-server
set secret <pass-phrase>
set port 1845
# Ensure radius requests originate from the mgmt interface
routing-instance mgmt_junos
set system authentication-order [radius password]
# Assign a default class for remote users
set system login user remote class super-user

### Setup Layer 3 Interface
# Change physical properties
edit interfaces ge-0/0/1
set speed 10m
set link-mode full-duplex

### Create VLAN
set vlans testvlan vlan-id 123
set vlans testvlan2 vlan-id 456

# Change logical properties
edit interfaces ge-0/0/1 unit 0
set vlan-id 50
edit family inet
set address

### Setup Access Port
# Change logical properties
edit interfaces ge-0/0/2 unit 0
set family ethernet-switching interface-mode access
set family ethernet-switching vlan members 123

### Setup Trunk Port
edit interfaces ge-0/0/3 unit 0
set family ethernet-switching port-mode trunk vlan members [testvlan testvlan2]

### Syslog Forwarding
* This is performed via the local syslog server rather than the Juniper CLI (messages found in /var/log/messages)
* To edit the configuration from the CLI use 'edit system syslog'.

### Commit changes

Wednesday 29 May 2019

Configuring Auto QoS on Cisco Switches

Auto QoS is a great feature included with the majority of switches running at least the LAN Base feature set. It will likely require some further tweaking after it's setup however it's a great base for applying QoS.

Cisco provides support for it's own telephony devices (surprise, surprise!) through CDP broadcasts. However in my case I am working with a different vendor and since not all switches will provide classification of packets I'm relying on the tagging being performed by the downstream devices.

It's very simple to setup - simply apply the following to the switch ports in scope (i.e. the ones connected to the telephony devices):

conf t
int range gi1/0/1-10
auto qos trust dscp

This will instruct the switch ports in scope to trust DSCP markings applied by the downstream devices (as I'm sure you're aware by default DSCP marking are typically stripped.)

The 'auto qos trust dscp' also enables qos globally for us and also applies a few other directives on the interface - so in reality a lot of the setup is performed for you - however in reality it's still crucial that you understand what each directives means!

do show run int gi1/0/1

interface GigabitEthernet1/0/1
 switchport access vlan 2000
 switchport mode access
 speed auto
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust dscp
 auto qos trust dscp
 spanning-tree portfast
 spanning-tree bpduguard enable

To verify QoS is turned on globally we can review:

show mls qos

and to review interface specific QoS information:

show mls qos interface gi1/0/1

We can also test QoS is successfully prioritising packets with iperf (tagging the traffic with a non zero DSCP value) e.g.:

iperf -c -i 1 -S 0xB8 -t 0

'0xB8' is the hexadecimal equivalent of TOS's 184 - which equates to DSCP's 'ef' / 46. According to the man page (at least in mine) the value must be in hexadecimal TOS form. There is an list of all of them available here.

We can then review the QoS counters for the interface with:

show mls qos interface gi1/0/1 stat

Thursday 23 May 2019

Cross compile packages for OpenWRT / LEDE

For this tutorial I'll be using Fedora 29 for the build host.

We'll install the necessary dependencies firstly:

sudo dnf install asciidoc binutils bzip2 flex git gawk intltool zlib gmake ncurses openssl-devel patchutils p5-extutils-makemaker unzip wget gettext libxslt zlib-devel boost-jam perl-XML-Parser libusb-devel dev86 sharutils java-1.7.0-openjdk-devel b43-fwcutter zip

The next step is to obtain the OpenWRT SDK which will allows us to cross-compile packages that we require on OpenWRT.

I'll be using a BT Home Hub 5A for this exercise - so I browse the releases:


Under the supplementary section you should find the SDK e.g.

lede-sdk-<version-number>-<vendor>-<model>_gcc-<version number>_musl-<version number>.Linux-<architecure>.tar.xz

We'll proceed by downloading and extracting it:

wget https://downloads.openwrt.org/releases/17.01.4/targets/lantiq/xrx200/lede-sdk-17.01.4-lantiq-xrx200_gcc-5.4.0_musl-1.1.16.Linux-x86_64.tar.xz

tar xvf lede-sdk-17.01.4-lantiq-xrx200_gcc-5.4.0_musl-1.1.16.Linux-x86_64.tar.xz && cd lede-sdk-17.01.4-lantiq-xrx200_gcc-5.4.0_musl-1.1.16.Linux-x86_64

The default feeds will be targeted at 17.01.4 and hence be missing fping - however the current master branch has fping available - so we'll add the following line to feeds.conf.default ensure it's indexed / available:

src-git fping https://github.com/openwrt/packages.git

Update the feeds (as defined in feeds.conf.default):

./scripts/feeds update -a

and grab fping with:

./scripts/feeds install fping

We'll generate our config file:

make menuconfig

Select 'Network' and ensure the fping package is marked with an 'M' and then save the changes to '.config'

Also make sure that cryptographic signing is disabled (otherwise the build process will fail): 'Global build settings' > Untick 'Cryptographically sign package lists' and hit Save.

We'll now attempt to compile fping:

make -j1 V=s

The binary is created in the following directory:


Finally upload the package via SFTP/SCP to the router and install it with opkg:

opkg install fping_4.2-1_mips_24kc.ipk

Wednesday 8 May 2019

Linux: Backup Options

There are countless ways to backup disks easily with Linux - however I'm going to demonstrate some of the more commonly used methods.

Forenote: Always ensure the discs are not in use / mounted while performing the below operations otherwise it is likely that new / changed files will be corrupted and will run into problems with the file system.

Backing up a disk with dd 

sudo dd if=/dev/xvda of=/mnt/usbdrive | sync

or better yet we can use a sane block size (dd uses 512 bytes by default):

sudo dd bs=16M if=/dev/xvda of=/mnt/usbdrive | sync

Backing up a disk with dd over ssh

Utilising SSH provides us with encryption - ideal for remote backups e.g. over public networks:

sudo ssh user@remote "dd if=/dev/xvda1 " | dd of=backup.gz

However it does introduce an overhead due to the encryption - so we can pipe it into gzip in order to speed things up:

sudo ssh user@remote "dd if=/dev/xvda1 | gzip -1 -" | dd of=backup.gz

Backing up a mounted system with rsync

If the system is currently mounted we can use rsync to perform a backup (ensuring we exclude certain directories such as /dev, /mnt etc):

sudo rsync -aAXv / --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found"} /mnt

In the above command we employ 'archive' mode that ensures symbolic links, devices, permissions, ownerships, modification times, ACLs, and extended attributes are preserved.

and over rsync over SSH

sudo rsync -aAXve ssh user@remote:/ --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*","/run/*","/mnt/*","/media/*","/lost+found"} /mnt

There are of course many other ways to skin a cat e.g. using netcat (which is significantly faster than dd over SSH - however lacks encryption.) 


Thursday 18 April 2019

Uploading ISO's to storage domains in oVirt

oVirt currently doesn't allow you to upload ISO's over its web interface - you'll need to use the cli to do this.

If you wish to upload an ISO to an ISO storage domain you should issue you should issue:

engine-iso-uploader --iso-domain <storage-domain-name> upload <path-to-iso>

Wednesday 10 April 2019

Tuesday 9 April 2019

Preventing kernel modules from being loaded at the bootloader / grub in CentOS 7 / RHEL

Although this will typically done with the mod probe there are situations where the need to disable specific kernel modules before loading the kernel are necessary. One such situation is while I was installing a fresh instance of CentOS on an older server.

At the CentOS bootloader select the relevant entry and hit tab. You should now be able to edit the Linux kernel (vmlinuz) boot parameters.

Simply append:


and hit enter.

This should theoretically work on all modern kernels / distros - so is not just limited to CentOS / RHEL.

Source: https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt

Saturday 16 March 2019

Using yum to download a package and all it's associated dependencies

This tutorial will demonstrate how to do a download-only of a package and all of it's dependancies.

To elaborate - I recently installed Fedora 29 on a Macbook, but unfortunately there was no native support for the WLAN driver.

However it was available from RPMFusion - packaged under 'akmod-wl' - however downloading this and all of it's dependancies would have taken a long time - so instead we can use plugin for yum called 'yum-downloadonly':

yum install yum-downloadonly

We can then issue something like follows to download the required packages on a working computer which is running Fedora 29 (though ensure it is running exactly the same minor version as well!):

sudo yum install --downloadonly --downloaddir=/tmp akmod-wl

However this is not ideal largely due to the fact that it will download all required packages that the system needs. If some of these packages are already installed on the system they will be omitted.

So instead I came up with the idea of quickly building a jail with the basic packages to get yum up and running (this would mimic the newly installed OS):

mkdir -p /chroot/fedora29/var/lib/rpm

rpm --root /chroot/fedora29 --initdb

yumdownloader --destdir=/var/tmp fedora-release
cd /var/tmp
rpm --root /chroot/fedora29 -ivh --nodeps fedora-release*rpm

sudo yum install --installroot=/chroot/fedora29 --downloadonly --downloaddir=/tmp akmod-wl

Then copy everything from the temp folder onto the new workstation and issue:

rpm -i *

Friday 15 March 2019

Generating a new UUID for XFS/EXT2/3/4 filesystems

Although very rare there will be circumstances were you encounter duplicate filesystem UUIDs.

Upon mounting one e.g.:

mount -t auto /dev/sdb1

mount: wrong fs type, bad option, bad superblock on /dev/sdb1

Tailing dmesg provides the clue as to what has gone wrong:

[ 1103.580854] XFS (xvdp1): Filesystem has duplicate UUID xxxxxx-yyyyyy-zzzzz-aaaa-bbbbbbbbbbb - can't mount

So we'll need to change the UUID of one of disks - to do this with an XFS filesystem we can use:

xfs_admin -U generate /dev/sdb1

and with the EXT family we can use:


<generated UUID>

tune2fs /dev/xvdp1 -U <generated UUID>

Finally attempt to remount:

mount -t auto /dev/sdb1

Tuesday 12 March 2019

Checking switch port bandwidth utilisation with SNMP / Nagios

In order to monitor port bandwidth utilization on Cisco switches via SNMP we'll firstly need to install a plugin from the Nagios Exchange called 'iftraffic2':

Download and install the plugin:

cd /usr/local/nagios/libexec
curl https://exchange.nagios.org/components/com_mtree/attachment.php?link_id=1720&cf_id=24 -O check_iftraffic
chmod +x check_iftraffic

The usage for the plugin is as follows:

./check_iftraffic -H <hostname> -C <community-string> -r -i <interface-name> -b <interface-capacity> -u <interface-unit> -w <warning-limit-percentage> -c <critical-limit-percentage>

We'll need to obtain the interface name of the interface we wish to poll - we can use snmpwalk to do this for us:

yum -y install net-snmp-utils
snmpwalk -v 2c -c <community-string> <hostname>

> IF-MIB::ifDescr.67 = STRING: Port-channel1
> IF-MIB::ifDescr.68 = STRING: Port-channel2
> IF-MIB::ifDescr.69 = STRING: Port-channel3
> IF-MIB::ifDescr.70 = STRING: Port-channel4

Note: '' is the OID for interface descriptions - more information can be found here.

We'll also need the interface capacity:

snmpwalk -v 2c -c <community-string> <hostname>

> IF-MIB::ifSpeed.67 = Gauge32: 2000000000
> IF-MIB::ifSpeed.68 = Gauge32: 2000000000
> IF-MIB::ifSpeed.69 = Gauge32: 2000000000
> IF-MIB::ifSpeed.70 = Gauge32: 2000000000

Now note that the OID '' returns the interface capacity in bits per second - so we'll need to convert this to gigabits per second (as the plugin doesn't support bits per second) - so we do:

2000000000 / 1000000000 = 2 (Gigabits)

For this example we'll use 'Port-channel1' - so the plugin would be executed as follows:

./check_iftraffic -H <hostname> -C <community-string> -r -i Port-channel1 -b 2 -u g -w 70 -c 85

The -b switch specifies our 2 Gbps and the -u switch instructs the plugin that we are giving the measurements in Gigabits.

If successfull you should have something like the following:

> Total RX Bytes: 1000.00 MB, Total TX Bytes: 2000.00 MB<br>Average Traffic: 5.75 MB/s (2.2%) in, 1.48 MB/s (0.6%) out| inUsage=2.2,50,70 outUsage=0.6,50,70 inAbsolut=10000000 outAbsolut=20000000

Now we simply need to setup the respective command and service definitions in nagios e.g.:

### commands.conf

# check switch port bandwidth
define command{
    command_name check_bandwidth
    command_line /usr/local/nagios/libexec/check_iftraffic -H $HOSTADDRESS$ -C $ARG1$ -r -i $ARG2$ -b $ARG3$ -u g -w 50 -c 70

### switches.conf

define service{
    use generic-service
    host_name SWITCH-STACK
    service_description HHSVRSTK Uplink: Bandwidth Utilization
    check_command check_bandwidth!<community-string>!Port-channel1!2
    normal_check_interval 1
    retry_check_interval 1

Monday 11 March 2019

Setup Nagios Core for SNMP traps with snmptrapd and snmptt

We'll firstly need to download and execute the installer script from Nagios.com:

sudo yum -y install bzip2

cd /tmp
wget https://assets.nagios.com/downloads/nagiosxi/scripts/NagiosXI-SNMPTrap-setup.sh
sh ./NagiosXI-SNMPTrap-setup.sh

This will install and setup snmptrapd and snmptt while ensuring the firewall is configured properly (udp/162 - however you may wish to lock this down further)

We'll then need to add our MIB's - for this example I'll be using a combination of SG200/300 switches and so will download the MIB's from:


In the commerical version of Nagios you can add these with ease through the GUI - however if you (like me) are using Core you'll need to use the addmib tool:

cd /tmp
unzip MIBs_Sx200_v1.4.1.03.zip
cd MIBs_Sx200_v1.4.1.03
mkdir /usr/share/snmp/mibs/Cisco-SG200-300
mv *.mib /usr/share/snmp/mibs/Cisco-SG200-300

and add them with:

find /usr/share/snmp/mibs/Cisco-SG200-300 -maxdepth 1 -type f -exec addmib {} \;

We can now send a test trap with:

snmptrap -v 2c -c public localhost '' linkUp ifDescr s eth0 ifAdminStatus i 1 ifOperStatus i 1

You should now see this logged to /var/log/snmptt/snmpttunknown.log

However this wasn't the case for me - everything I was sending was being dropped / didn't show up in the snmptt log. After inspecting the service log for snmptrapd I quickly noticed the following warning:

Mar 11 14:51:33 host.internal snmptrapd[2752]: NET-SNMP version 5.7.2
Mar 11 14:51:33 host.internal systemd[1]: Started Simple Network Management Protocol (SNMP) Trap Daemon..
Mar 11 15:31:28 host.internal snmptrapd[2752]: No access configuration - dropping trap.
Mar 11 15:31:41 host.internal snmptrapd[2752]: No access configuration - dropping trap.

This behaviour is expected by default - as the snmptrapd team decided (wisely) to utilize authentication for incoming SNMP traps - however oddly this shouldn't have been an issue since the installer script from nagios added 'disableAuthorization yes' to '/etc/snmp/snmptrapd.conf' - however after reloading the service all was well - so I can only imagine the config had been added and the service did not reload / restart as intended.

tailing /var/log/snmptt/snmptt.log shows:

Mon Mar 11 16:03:56 2019 . Normal "Status Events" localhost - A linkUp trap signifies that the SNMP entity, acting in an eth0 up up

NOTE: Unknown MIB's will be sent to /var/log/snmptt/snmpttunknown.log

You'll also notice that in the nagios logs the following warning:

'Warning:  Passive check result was received for service 'SNMP Traps' on host 'localhost', but the service could not be found!'

So it looks like snmptt is successfully sending the information to nagios - however nagios does not know what to do with it!

We'll proceed by defining the service it's trying to submit data for:

define service {
  name SNMP Traps
  service_description SNMP Traps
  active_checks_enabled 1 ; Active service checks are enabled
  passive_checks_enabled 1 ; Passive service checks are enabled/accepted
  parallelize_check 1 ; Active service checks should be parallelized
  process_perf_data 0
  obsess_over_service 0 ; We should obsess over this service (if necessary)
  check_freshness 0 ; Default is to NOT check service 'freshness'
  notifications_enabled 1 ; Service notifications are enabled
  event_handler_enabled 1 ; Service event handler is enabled
  flap_detection_enabled 1 ; Flap detection is enabled
  process_perf_data 1 ; Process performance data
  retain_status_information 1 ;
  retain_nonstatus_information 1 ;
  check_command check-host-alive ;
  is_volatile 1
  check_period 24x7
  max_check_attempts 1
  normal_check_interval 1
  retry_check_interval 1
  notification_interval 120
  notification_period 24x7
  notification_options w,u,c,r
  contacts contact1,contact2
  register 0

define service {
  use SNMP Traps
  host_name localhost
  service_description TRAP
  check_interval 120

We can then test the serviced is working correctly with:

/usr/local/nagios/libexec/eventhandlers/submit_check_result localhost TRAP 2 "TESTING"

The changes should now be reflected on the nagios check status.

The next step is to load the relevant MIB files so we can translates the O.I.D's. In this tutorial we will be checking link status of a port so we'll need 'IF-MIB..txt' (which should come as part of the default installation - if not see here: http://www.net-snmp.org/docs/mibs/IF-MIB.txt)

We'll proceed by generating the snmptt.conf with:

rm -rf /etc/snmp/snmptt.conf
snmpttconvertmib --in=/usr/share/snmp/mibs/IF-MIB.txt --out=/etc/snmp/snmptt.conf --exec='/usr/local/nagios/libexec/eventhandlers/submit_check_result $r TRAP 2'

Open up the snmptt.conf file and ensure that the EXEC line for EVENT 'linkUp' returns 0 opposed to '2' and leave EVENT 'linkDown' as it is.

and reload the service with:

sudo service snmptt reload

We can then test it with: snmptrap -v 2c -c public localhost '' linkDown ifDescr s fa0/1 ifAdminStatus i 0 ifOperStatus i 0

and then check it reverts with:

snmptrap -v 2c -c public localhost '' linkUp ifDescr s fa0/1 ifAdminStatus i 0 ifOperStatus i 0

Thursday 7 March 2019

Setting up NPS / RADIUS for use with a Cisco 2960X

Below is a sample configuration to get up and running with Radius:

2960X Configuration

conf t
radius server <server-name>
address ipv4 <server-ip>
key <shared-secret>

aaa new-model # create new aaa model
aaa authentication login default group radius local-case # allow radius and local user authentication by default
aaa authorization exec default group radius local-case if-authenticated #  allow radius and local user authorisation by default

aaa accounting system default start-stop group radius # only account for radius

umasks: Ensuring httpd / apache is assigning the appropriate permissions on files / directories

I came across an issue the other day where the user httpd was running as was part of group that had been assigned permissions to the www root. Typically the user httpd runs under will be the owner of these files and directories and as a result will almost always have adequate permissions to read, write and execute. However in this case because it was part of a group instead the default umask setting of 022 was preventing the httpd user from writing to the files.

The umask can be worked out as follows - for example a umask of 002:

Directories: 777 - 002 = 775

Files: 666 - 002 = 664

i.e. the owner and group are able to read, write and execute directories and everyone else can only read and execute them. While the owner and group can write, write files and everyone else can only read them.

In order to apply these to httpd we can simply add the following line under the service stanza in /lib/systemd/system/httpd.service:

vim /lib/systemd/system/httpd.service

UMask = 0002

and finally ensure httpd is restarted with:

sudo systemctl daemon-reload
sudo systemctl httpd restart

Tuesday 19 February 2019

Debugging with the puppet agent command

To enable debugging on a puppet agent you can issue:

puppet agent --test --noop --debug --trace

The above command does not actually carry out any changes - it only simulates what could have happened. Removing the '--noop' switch allows us to actually carry out those changes e.g.:

puppet agent --test --debug --trace

Tuesday 5 February 2019

Creating your first Puppet module

This tutorial will be a quick demonstration of how to create, build and test a basic puppet module.

Firstly generate the puppet module with:

mkdir ~/workbench && cd ~/workbench

puppet module generate username-webmin --skip-interview

This will generate the following directory structure:

└── webmin (module directory)
    ├── examples
    │   └── init.pp (example of how to initailize the class)
    ├── Gemfile (used to describe dependancies needed for the module / Ruby)
    ├── manifests (holds the module manifests i.e. contains a set of instructions that need to be run)
    │   └── init.pp (the default manifest - it defines our main class: webmin)
    ├── metadata.json (contains module metadata like author, module description, dependancies etc.)
    ├── Rakefile (essentially a makefile for Ruby)
    ├── README.md (contains module documentation)
    └── spec (used for automated testing - is optional)
        ├── classes
        │   └── init_spec.rb
        └── spec_helper.rb

If we do a cat on the init.pp within the examples directory:

cat examples/init.pp

include ::webmin

This include statement can be used in other manifests in Puppet and simply imports the webmin class.

In older modules you might have seen a params manifest (params.pp) - this design pattern has recently been replaced with the release of Hiera v5 with in-module data (https://github.com/puppetlabs/best-practices/blob/master/puppet-module-design.md)

This means that we need to construct our Hiera hierarchy in the form of 'hiera.yaml' in our module. This will typically look like this:

cat webmin/hiera.yaml

version: 5

  datadir: 'data'
  data_hash: 'yaml_data'

  - name: 'Full Version'
    path: '%{facts.os.name}-%{facts.os.release.full}.yaml'

  - name: 'Major Version'
    path: '%{facts.os.name}-%{facts.os.release.major}.yaml'

  - name: 'Distribution Name'
    path: '%{facts.os.name}.yaml'

  - name: 'Operating System Family'
    path: '%{facts.os.family}-family.yaml'

  - name: 'common'
    path: 'common.yaml'

Note: It's important to keep in mind that the hierarchy is reusable e.g. avoid adding in specific networks or environments.

We'll also need to create our data directory to hold our yaml data in:

mkdir webmin/data
touch webmin/data/Debian-family.yaml
touch webmin/data/RedHat-family.yaml
touch webmin/data/common.yaml

For the sake of time and simplicity I have confined the yaml data to a few OS families.

As seen in the hierarchy anything defined within the 'Operating System Family' take presidense over anything in 'common'. However if this module were to be applied to say OpenSUSE only settings in common.yaml would be applied - so it's important to ensure that there are suitable defaults in common data.

We'll proceed by defining our variables within the init.pp (manifests directory):

class webmin (
  Boolean $install,
  Optional[Array[String]] $users,
  Optional[Integer[0, 65535]] $portnum,
  Optional[Stdlib::Absolutepath] $certificate,
  notify { 'Applying class webmin...': }

In the above class we are defining several variables that will allow the user to customise how the module configures webmin. As you'll notice three of them are optional - so if they are undefined we'll provide the defaults our self in the manifest.

At this point we might want to verify the syntax in our init.pp manifest is valid - we can do this with:

puppet parser validate webmin/manifests/init.pp

We will also create two more classes - one for setup / installation of webmin and the other for configuration of it:

touch /webmin/manifests/install.pp && touch /webmin/manifests/configure.pp

We'll declare these in our init.pp like follows:

class webmin (
  Boolean $install,
  String $webmin_package_name,
  Optional[Array[String]] $users,
  Optional[Integer[0, 65535]] $portnum,
  Optional[Stdlib::Absolutepath] $certificate,
  notify { 'Applying webmin class...': }

  contain webmin::install
  contain webmin::configure

  -> Class['::webmin::configure']


And then declare the classes:

cat /webmin/manifests/install.pp

# @summary
#   This class handles the webmin package.
# @api private
class webmin::install {

  if $webmin::install {

    package { $webmin::webmin_package_name:
      ensure => present,

    service { $webmin::webmin_package_name:
    ensure    => running,
    enable    => true,
    subscribe => Package[$webmin::webmin_package_name],




cat /webmin/manifests/configure.pp

# @summary
#   This class handles webmin configuration.
# @api private
class webmin::configure {



You'll notice that although we have defined variables in the parent class we have not actually defined what these will be yet. This is where Hiera will come in - so to data/common.yaml we add:

webmin::webmin_package_name: webmin
webmin::install: true
webmin::users: ~
webmin::portnum: 10000
webmin::certificate: ~

We'll also need to add repositories for webmin - as by default (to my knowledge at least) it's not included in any of the base repositories included with Redhat or Debian.

In order to configure repositories for particular operating systems we will need to use the yum and apt modules. Module dependencies are defined in the 'metadata.json' file - for example:

"dependencies": [
  { "name": "puppet/yum", "version_requirement": ">= 3.1.0" },
  { "name": "puppetlabs/apt", "version_requirement": ">= 6.1.0" },
  { "name": "puppetlabs/stdlib", "version_requirement": ">= 1.0.0" }

So your metadata.json would look something like:

  "name": "username-webmin",
  "version": "0.1.0",
  "author": "Joe Bloggs",
  "summary": "A module used to perform installation and configuration of webmin.",
  "license": "Apache-2.0",
  "source": "https://yoursite.com/puppetmodule",
  "project_page": "https://yoursite.com/puppetmodule",
  "issues_url": "https://yoursite.com/puppetmodule/issues",
  "dependencies": [
  { "name": "puppet/yum", "version_requirement": ">= 3.1.0" },
  { "name": "puppetlabs/apt", "version_requirement": ">= 6.1.0" },
  { "name": "puppetlabs/stdlib", "version_requirement": ">= 1.0.0" }
  "data_provider": null

Because we haven't packaged up the module yet we'll need to install the dependencies manually i.e.:

puppet module install puppetlabs/apt
puppet module install puppet/yum

We'll then need to copy them to our working directory (~/workbench) e.g.:

cp -R /etc/puppetlabs/code/environments/production/modules/{yum,apt,stdlib} ~/workbench

We'll use Hiera to configure the OS specific settings for the repositories:

cat webmin/data/RedHat-family.yaml

version: 5

    - 'webmin_repo'

        ensure: 'present'
        enabled: true
        descr: 'Webmin Software Repository'
        baseurl: 'https://download.webmin.com/download/yum'
        mirrorlist: 'https://download.webmin.com/download/yum/mirrorlist'
        gpgcheck: true
        gpgkey: 'http://www.webmin.com/jcameron-key.asc'
        target: '/etc/yum.repos.d/webmin.repo'

cat webmin/data/Debian-family.yaml

version: 5

        location: 'http://download.webmin.com/download/repository'
        release: 'stretch'
        repos: 'contrib'
        key: '1B24BE83'
        key_source: 'http://www.webmin.com/jcameron-key.asc'
        include_src: 'false'

Let's check everything looks good:

puppet parser validate manifests/*.pp

We'll now try and apply our manifests and see if they apply correctly:

puppet apply --modulepath=~/workbench webmin/tests/init.pp

With any luck you will now have webmin installed and should also see our notify messages we included earlier.

Finally we can publish the module with:

sudo puppet module build webmin-reloaded

We can now distribute this internally or alternatively upload it for public consumption at the Puppet Forge.

To test the built module you can run:

sudo puppet module install ~/Workbench/username-webmin-0.1.0.tar.gz

Wednesday 30 January 2019

php-fpm Log Location (RHEL / PHP7)

More of a note to myself but php-fpm no longer appears to write logs a long with the web server's (at least not on 7.0.27 on RHEL.

The various logs are written to:


Friday 25 January 2019

Linux: Server Not Syncing with NTP (Stuck in INIT state)

The service was confirmed running and set to start on boot:

sudo service ntpd status

Redirecting to /bin/systemctl status ntpd.service
● ntpd.service - Network Time Service
   Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled; vendor preset: disabled)
   Active: active (running) since Fri 2019-01-25 12:11:16 GMT; 13min ago
  Process: 32649 ExecStart=/usr/sbin/ntpd -u ntp:ntp $OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 32650 (ntpd)
   CGroup: /system.slice/ntpd.service
           └─32650 /usr/sbin/ntpd -u ntp:ntp -g

We can quickly check if NTP is not properly synchronised with the 'ntpstat' command:

> ntpstat
  time server re-starting
   polling server every 8 s

We can also check the connection status of the ntp server with:

ntpq -p

     remote           refid      st t when poll reach   delay   offset  jitter
 meg.magnet.ie   .INIT.          16 -    -  512    0    0.000    0.000   0.000
 ec2-52-53-178-2 .INIT.          16 -    -  512    0    0.000    0.000   0.000
 chris.magnet.ie .INIT.          16 -    -  512    0    0.000    0.000   0.000

From the above (specifically the INIT state) my immediate thought was that it was a firewall issue somewhere. 

It's worth checking the EC2 instance SG to ensure that the server can reach udp/123 outbound. However remember to also check the Network ACL (it's stateless) and ensure that udp/123 can get out as well.

ntpd was attempting to initiate a connection with the ntp servers however never got past this phase. After confirming the firewall rules, sg's, ACL's etc.  (i.e. 123/udp outbound and ensuring that session states were maintained) I decided to directly query one of the NTP servers with:

ntpdate -d meg.magnet.ie

This was successful so it seemed something else was causing this.  

In the end I realised it was failing because ntpd was binding with localhost and was attempting to access the external NTP servers (obviously failing because they are unroutable from a loopback device!)


listen interface


listen interface

in /etc/ntp.conf  and restarting ntpd resolves the issue:

     remote           refid      st t when poll reach   delay   offset  jitter
 x.ns.gin.ntt.ne   2 u   27   64    1   11.206   52.795   0.000      2 u   26   64    1   12.707   53.373   0.000
 ntp3.wirehive.n     2 u   25   64    1   14.334   53.125   0.000
 h37-220-20-12.h      2 u   24   64    1   19.211   53.350   0.000