Author Archives: Vyacheslav

Using the firmware password on a Mac

To enable or disable the firmware password on the Mac and MacBooks, you must press the Command+R keys or the Option(Alt) key after turning on the sound, then select the menu “Utilities“-“Firmware password utility “and select” Enable firmware password “in the window that opens and set the password.
Continue reading “Using the firmware password on a Mac”

Monitoring BGP in Zabbix

I’ll give an example of a simple check whether something is running on TCP port 179 which uses BGP.

Create the following data item with the name Zabbix in the new Zabbix template or right in the network node “Template App BGP Service” (where 192.168.10.2 is the address of the host on which the performance of the BGP is checked):

Name: BGP service is running
Type: Zabbix agent
Key: net.tcp.service[tcp,192.168.10.2,179]
Type of information: Numeric (positive integer)
Data type: Decimal
Displaying the value: Service state

If Zabbix-agent is installed on the node, then we will create two data elements and in the field “Key:” we will indicate:

proc.num[bgpd]
proc.num[zebra]

If the data element reports 0, then BGP does not work, or the port is closed, if 1 is OK.

Accordingly, we will add a trigger that will notify about the idle BGP:

Name: BGP does not work on {HOST.NAME}
Expression: {Template App BGP Service:net.tcp.service[tcp,192.168.10.2,179].max(#3)}=0

Все.

Monitoring Samba in Zabbix

I will give an example of monitoring the number of running Samba processes, as well as creating a triggering trigger when there are no running processes.
In a system with Samba, a Zabbix agent must be installed.
See my popular articles about Zabbix.

Create a template, for example, with a name “Template Service Samba” and add the following data item to it:

Name: Number of processes nmbd
Type: Zabbix agent
Key: proc.num[nmbd]

Similarly, we create for smbd.
You can also create data items that represent the amount of memory used by the process, in which case the key will look like this:

proc.mem[nmbd,,sum]

And also add graphics for them.

Now add a trigger for each process to see when the process is not running:

Name: Does not work nmbd on {HOST.NAME}
Expression: {Template Service Samba:proc.num[nmbd].max(1)}<1

Done.

How to fix “client denied by server configuration” error

I noticed once in the browser the error of opening a GoIP SMS crypt:

[authz_core:error] [pid 23415] [client 192.168.56.1:50388] AH01630: client denied by server configuration: /usr/local/goip/

As it turned out, the script was supposed to work in apache2 version 2.2 and in the file /etc/apache2/conf-enabled/goip.conf the following parameters were specified:

Order allow,deny
Allow from all

And in my case, an apache2 version of the newer 2.4 was installed, in which access control is configured a little differently, and to fix the error, change the above parameters to:

Require all granted

Or to restrict access to IP by resolving locally and to specified addresses:

Require local
Require ip 192.168.56.1 192.168.22.10

And restart apache2 to apply the changes:

sudo service apache2 restart

See also:
Access Control Apache2

How to fix the error “Invalid command ‘RewriteEngine'”

I noticed one error after installing FreePBX:

Invalid command ‘RewriteEngine’, perhaps misspelled or defined by a module not included in the server configuration

To solve it, you need to activate the rewrite module in apache2:

sudo a2enmod rewrite

And restart apache2 to apply the changes:

sudo service apache2 restart

Done.

Configuring DHCP relay on Cisco

On the test, I’ll take the Cisco Catalyst 6509-E switch and configure it to forward DHCP packets to the DHCP server.
The switch is configured as L3 with assigned IP addresses in each VLAN.

Connect to the switch through the console or telnet and go to the configuration mode:

enable
configure t

Let’s assume the DHCP server address is 192.168.11.1 and we want to configure the transfer of DHCP broadcast packets to it on VLAN 100, for this we execute the commands:

interface Vlan100
ip helper-address 192.168.11.1
exit

Exit the configuration mode and save the configuration:

exit
write

Done.