How to verify SPF/DKIM/DMARC/DomainKey/RBL tests parsed on the email.
Hi All
In some situations , when an email is blocked by the antispam device , you need to analyze the headers to findout the actual root cause. However , sometimes the blocked reasons shown by the antispam device are not descriptive especially when you are troubleshooting DKIM related failures.
This is crucial as we need notify the sender’s domain owner to rectify the issues. In these cases you could use the below tool to analyze the tests performed in the email and findout the actual reason for the email blockage in a much descriptive manner.
https://www.appmaildev.com/en/dkimfile
I found it very useful , and thought of sharing it with the community.
Good luck guys.
DCPromo Fails – The directory service is missing mandatory configuration information
Last week , we worked on a AD migration project. This project involved deploying a Windows 2016 based Domain Controller and then decommission the Windows 2008R2 domain controller.
We successfully transferred the FSMO roles . During the decommissioning process when we ran the dcpromo command we received the error “The directory service is missing mandatory configuration information”
During the troubleshooting the MS KB (https://docs.microsoft.com/en-us/troubleshoot/windows-server/identity/dcpromo-demotion-fails) was pointing us to correct direction. The issue was related to fsmoroleowner attribute on CN=Infrastructure is not set properly. In my case it was pointing to the server which I am trying to demote.
You can see this by opening ADSI Edit;
Right click the ADSI Edit root and click on Connect to…
Use the following connection point: DC=DomainDNSZones,DC=abc,DC=local (Replace it with your actual AD DNS Zone)
Click on Default Naming Context [DC.abc.local] to populate it.
Click on DC=DomainDNSZones,DC=abc,DC=local folder.
Double click on CN=Infrastructure.
Locate the fSMORoleOwner attribute
Ensure you connect to DC=ForestDNSZones as well to verify the attribute.
In my case DomainZones was showing the correct DC .But the ForestDNSZones pointing to the Windows 2008R2 Server.
I have tried the manual method using the ADSI Edit to change the value. However it was failing with the error “The role owner attribute could not be read”
In this case you need to refer the MS KB https://docs.microsoft.com/en-us/troubleshoot/windows-server/identity/dcpromo-demotion-fails to create the .vbs file to fix this issue.( I have seen suggestions to run the dcpromo /forceremoval instead and then run a metadata cleanup. I do not recommend this approach)
The script provided in the KB does not work due to incorrect end statements. Luckily the Blogger veducate.co.uk (https://veducate.co.uk/dcpromo-fails-missing-mandatory-configuration/) have provided a fixed version.
NOTE: You need to run these commands from the current owner of the FSMO roles.
Create a .vbs file via CMD
fsutil file createnew fixfsmo.vbs 0
Copy the below contents to the file
================================================
const ADS_NAME_INITTYPE_GC = 3
const ADS_NAME_TYPE_1779 = 1
const ADS_NAME_TYPE_CANONICAL = 2
set inArgs = WScript.Arguments
if (inArgs.Count = 1) then
‘ Assume the command line argument is the NDNC (in DN form) to use.
NdncDN = inArgs(0)
Else
Wscript.StdOut.Write “usage: cscript fixfsmo.vbs NdncDN”
End if
if (NdncDN <> “”) then
‘ Convert the DN form of the NDNC into DNS dotted form.
Set objTranslator = CreateObject(“NameTranslate”)
objTranslator.Init ADS_NAME_INITTYPE_GC, “”
objTranslator.Set ADS_NAME_TYPE_1779, NdncDN
strDomainDNS = objTranslator.Get(ADS_NAME_TYPE_CANONICAL)
strDomainDNS = Left(strDomainDNS, len(strDomainDNS)-1)
Wscript.Echo “DNS name: ” & strDomainDNS
‘ Find a domain controller that hosts this NDNC and that is online.
set objRootDSE = GetObject(“LDAP://” & strDomainDNS & “/RootDSE”)
strDnsHostName = objRootDSE.Get(“dnsHostName”)
strDsServiceName = objRootDSE.Get(“dsServiceName”)
Wscript.Echo “Using DC ” & strDnsHostName
‘ Get the current infrastructure fsmo.
strInfraDN = “CN=Infrastructure,” & NdncDN
set objInfra = GetObject(“LDAP://” & strInfraDN)
Wscript.Echo “infra fsmo is ” & objInfra.fsmoroleowner
‘ If the current fsmo holder is deleted, set the fsmo holder to this domain controller.
if (InStr(objInfra.fsmoroleowner, “\0ADEL:”) > 0) then
‘ Set the fsmo holder to this domain controller.
objInfra.Put “fSMORoleOwner”, strDsServiceName
objInfra.SetInfo
‘ Read the fsmo holder back.
set objInfra = GetObject(“LDAP://” & strInfraDN)
Wscript.Echo “infra fsmo changed to:” & objInfra.fsmoroleowner
End if
End if
=================================================
Run the file twice as below
1) cscript fixfsmo.vbs dc=forestdnszones,dc=abc,dc=local
2) cscript fixfsmo.vbs dc=domaindnszones,dc=abc,dc=local
Voila , The fsmoroleowner attribute got updated with the correct server name , and I was able to demote the server successfully.
Source: (Helped me to fix the syntax errors on script provided by Microsoft)
DCPromo Fails – The directory service is missing mandatory configuration information
Thanks.
How to create a Ubuntu 18.04.5 template in VSphere ESXi 6.7
As usual you need to create a VM and install Ubuntu in to it. Thereafter you need to follow the below steps to strip out the unique data being propagated to the VM’s you create from the template.
+Update the OS
#sudo apt -y update
#sudo apt -y upgrade
+Clear audit logs
truncate -s0 /var/log/wtmp
truncate -s0 /var/log/lastlog
+Clear the tmp
#rm -rf /tmp/*
rm -rf /var/tmp/*
+Clear the SSH
#rm -f /etc/ssh/ssh_host_*
+Reset the hostname
#sed -i ‘s/preserve_hostname: false/preserve_hostname: true/g’ /etc/cloud/cloud.cfg
#truncate -s0 /etc/hostname
#hostnamectl set-hostname localhost
+Clean apt
#apt clean
+Remove the default *.yaml file from the /etc/netplan. The VMware customizaion will create it’s own file 99-netcfg-vmware.yaml.
#rm -f /etc/netplan/*.yaml
+Reset the machine id
#echo -n > /etc/machine-id
+Clear the history & shutdown the VM
#history -c
#shutdown -h now
On the vCenter you need to create a VM Customization specification to be used when deploying the VM’s from the template(Refer:How to create a RHEL 7 template in VSphere ESXi 6.7 for steps).
However , when I created the VM’s from this template I realised that
- All the VM’s are having the same hostid. Some applications uses the hostid in their licensing .Thus, it has to be unique across the VM’s. Since I did not find a way to solve this while deploying the VM’, I had to do a manual modification as mentioned below on the VM’s after it being created.
#vi /etc/hosts
replace the line “127.0.1.1 localhost” with
your IP FQDN Hostname (E.g: 1.1.1.1 server.test.local server). - You need to manually select the “Connected” option in The VM network Adapter in the VM properties.
The Microsoft Exchange Replication service couldn’t find a valid configuration for database ‘mydb’ on server ‘server1’. Error: An Active Manager operation failed. Error: The active copy for database could not be determined:
Recently one of our customer had an Exchange Server outage. Whereas one of the node from 2 node DAG was not able to communicate with other server. We tried to rebooting the server but no luck . The symptoms were
– Cluster service was not starting.
– On the other node FCM was not able to connect to the DAG cluster.
– Unable to open the ECP/OWA.
– Outlook / Mobile Users cannot access their mailboxes.
The environment consist of 2 Exchange Server 2016 & DAG.
So we started with removing the failed node by typing the below commands in the healthy exchange server:
# Open Exchange PowerShell
#Get-ClusterNode -Name node1 | Remove-Clusternode
# net stop clussvc
# net start clussvc
# Remove-DatabaseAvailabilityGroupServer -Identity “DAG Name” -MailboxServer “Failed Exchange Server Name” -ConfigurationOnly
# Get-ClusterNode “Failed Exchange Server Name” | Remove-ClusterNode
However , still no luck. Then we tried to remove the mailbox database copies form the failed node(I believe the copies were active on the second server) we got a new error stating that “Mailbox databse copies cannot be disabled on the Databases with circular logging enabled. So we had to remove the circular logging and then delete the database copies.
#Get-MailboxDatabse | Set-MailboxDatabase -CircularLoggingEnabled $False
# Get-MailboxDatabaseCopy -Identity “DatabaseName” |Remove-MailboxDatabaseCopy -Identity “DatabaseName\ServerName”
Now it is the time for mounting the databses: When we ran the below command
#Get-MailboxDatabase | Mount-Database
We received the below error”
Failed to mount database “———-“. Error: An Active Manager operation failed. Error: An Active Manager operation
encountered an error. To perform this operation, the server must be a member of a database availability group, and the
database availability group must have quorum. Error: Automount consensus not reached (Reason: FSW boot time did not
match (FSW-Remote: 2020-10-01T11:37:09.4930830Z FSW-Reg: 0001-01-01T00:00:00.0000000)). [Server:———-]
+ CategoryInfo : InvalidOperation: (—-:ADObjectId) [Mount-Database], InvalidOperationException
+ FullyQualifiedErrorId : [Server=————,RequestId=5022acdd-0c48-4584-b2eb-1d0a2c692f0d,TimeStamp=10/7/2020
11:09:14 AM] [FailureCategory=Cmdlet-InvalidOperationException] BCF4F25E,Microsoft.Exchange.Management.SystemConfi
gurationTasks.MountDatabase
Here , we wanted to check the DAG status
#Get-DatabaseAvailabilityGroup -status
Output :
WARNING: Unable to get Primary Active Manager information due to an Active Manager call failure. Error: An Active
Manager operation failed. Error: An Active Manager operation encountered an error. To perform this operation, the
server must be a member of a database availability group, and the database availability group must have quorum. Error:
Automount consensus not reached (Reason: FSW boot time did not match (FSW-Remote: 2020-10-01T11:37:09.4930830Z FSW-Reg:
0001-01-01T00:00:00.0000000)). [Server: ———-]
Name : DAGName
Memberservers: {Server1}
Operational Servers {}
The output confirmed that there a no operatinal servers. So we had to restart the DAG with the surviving node.
#Start-DatabaseAvailabilityGroup -Identity “DAGNAME” -MailboxServer ServerName”
Now the Get-DatabaseAvailabilityGroup -status cmd will gave the below output:
Name : DAGName
Memberservers: {Server1}
Operational Servers {Server1}
Now it is the time for mounting all the databases:
Get-MailboxDatabase | Mount-Database
Voila , The MailboxDatabases were started mounting and the ECP access is restored.
Free Radius : Auth: (0) Invalid user (Rejected: User-Name contains multiple ..s): [xxx]
Recently we performed a Yum update on our Free Radius Server. The newer version is FreeRADIUS Version 3.0.13. At that time , we started receiving complains from the users that they are not able to login to the network devices.
After reviewing the logs , we noticed the error “Auth: (0) Invalid user (Rejected: User-Name contains multiple ..s)” being logged during the authentication. This is due to the changes applied in the filter file(/etc/raddb/policy.d/filter ).
Before Update:
if (&User-Name =~ /\\.\\./ ) {
After Update:
if (&User-Name =~ /\.\./ ) {
The new Regex syntax style doesn’t escape backslashes anymore. So you need to ensure that the correct_escapes = true property is set in /etc/raddb/radiusd.conf.
How to update ESXi 6.x using an Offline Bundle
We all know there are multiple ways to upgrade the ESXi to the desired version. In this post I am going to discuss about upgrading the ESXi using an offline bundle. In my opinion this method is much convenient when you are having a single ESXi host , or you want a more controlled upgrade process. The steps are very minimal.(Please make sure that , you have powered off all the VM’s and the Host is put to the Maintenance mode)
– Download the ESXi bundle and upload it to a Datastore.
– Login to the ESXi via SSH.
Run the below command to verify the bundle
#esxcli software sources profile list -d /vmfs/volumes/datastore1/VMware-ESXi-6.7.0-Update3-15160138-HPE-Gen9plus-670.U3.10.5.5.25-Mar2020-depot.zip
Output:
Thereafter , run the below command to install the file.
#esxcli software profile update -p HPE-ESXi-6.7.0-Update3-Gen9plus-670.U3.10.5.5.25 -d /vmfs/volumes/datastore/VMware-ESXi-6.7.0-Update3-15160138-HPE-Gen9plus-670.U3.10.5.5.25-Mar2020-depot.zip
-p xxxxxxxxx (Name of the ESXi bundle as per the output).
Once the process is completed you need to reboot the server(The host may restart automatically for the 2nd time as well).
Update1: In case if you receive an error “Could not find a trusted signer” ., when you try to install you can run the same command with –no-sig-check as below:
#esxcli software profile update -p HPE-ESXi-6.7.0-Update3-Gen9plus-670.U3.10.5.5.25 -d /vmfs/volumes/datastore/VMware-ESXi-6.7.0-Update3-15160138-HPE-Gen9plus-670.U3.10.5.5.25-Mar2020-depot.zip –no-sig-check
How to properly update kernel in RHEL/CentOS 7/8 Linux
When you perform a yum update in CentOS 7 or higher , you will notice the newer kernel version is not reflected. You can use the below commands to verify the current version.
#uname -r
#hostnamectl
You can confirm whether the new kernel is installed successfully or not by using the command below;
#yum list kernel
#grep saved /boot/grub2/grubenv
In order to apply the kernel you need to restart the server.
In some instances you need to manually set the correct kernel version to boot by using the below commands;
#awk -F\’ ‘$1==”menuentry ” {print i++ ” : ” $2}’ /etc/grub2.cfg
(If you have multiple versions installed all of them will be listed with 0 , 1 & etc. In the example the newer version is 0,)
#sudo grub2-set-default 0
Source1: https://www.howtoforge.com/
Source2: https://www.golinuxcloud.com/
“ Error 432 4.3.2 STOREDRV.Deliver; recipient thread limit exceeded in Exchange 2016
One of our customer complained that the Internal E-mails are not being delivered. When we checked the Queue Viewer we observed the emails are stuck at the queue with the error “Error- 432 4.3.2 STOREDRV.Deliver; recipient thread limit exceeded”
This could be due to large number of emails being sent internally(either to one mailbox / several mailboxes).In our case , the customer’s processing server was down for some days, and when it was restored it started sending all the backlog emails.
To overcome this issue we had to temporarily disable the throttling , by adding the below text in the EdgeTransport.exe.config file(located in the Exchange Bin Folder)
add key=”MailboxDeliveryThrottlingEnabled” value=”False”
(Some articled recommends to add the value in the MSExchangedelivery.exe.config file instead).
Thereafter , you need to restart the MS Exchange Transport & Exchange Mailbox Transport Delivery services.
In case if you don’t completely disable the throttling you could add the below keys.
add key=”RecipientThreadLimit” value=”2″
add key=”MaxMailboxDeliveryPerMdbConnections” value=”3″
Good Luck.
How to modify the iSCSI initiator ID in Linux
When you deploy Linux VM’s using a Template (in ESXi) ,you may come across a situation , where the iSCI initiator ID on these VM’s will be identical. To resolve this issue we need to modify the iscsi initiator ID’s.
In case if you have logged in to the iscsi session already you need to log out first.
#iscsiadm -m node -T iqn.xxxxxxxxxxxxxx -p iscsiserver-ip -u
Thereafter:
backup the file initiatorname.iscsi
#cp /etc/iscsi/initiatorname.iscsi /etc/iscsi/initiatorname.iscsi.bak
#echo “InitiatorName=`/sbin/iscsi-iname`” > /etc/iscsi/initiatorname.iscsi
You can login again to the iscsi session
#iscsiadm -m node -T iqn.xxxxxxxxxxxxxx -p iscsiserver-ip -l
Source:https://www.thegeekdiary.com/
How to view the Network Configuration in AHV
Use the following commands to view the configuration of the network elements.
Before you begin
Log on to the Acropolis host with SSH.
Procedure
- To show interface properties such as link speed and status, log on to the Controller VM, and then list the physical interfaces.
nutanix@cvm$ manage_ovs show_interfaces
Output similar to the following is displayed:
name mode link speed eth0 1000 True 1000 eth1 1000 True 1000 eth2 10000 True 10000 eth3 10000 True 10000
- To show the ports and interfaces that are configured as uplinks, log on to the Controller VM, and then list the uplink configuration.
nutanix@cvm$ manage_ovs –bridge_name bridge show_uplinks
Replace bridge with the name of the bridge for which you want to view uplink information. Omit the –bridge_name parameter if you want to view uplink information for the default OVS bridge br0.Output similar to the following is displayed:
Bridge: br0
Bond: br0-up
bond_mode: active-backup
interfaces: eth3 eth2 eth1 eth0
lacp: off
lacp-fallback: false
lacp_speed: slow
- To show the bridges on the host, log on to any Controller VM with SSH and list the bridges:
nutanix@cvm$ manage_ovs show_bridges
Output similar to the following is displayed
Bridges: br0
- To show the configuration of an OVS bond, log on to the Acropolis host with SSH, and then list the configuration of the bond.
root@ahv# ovs-appctl bond/show bond_name
For example, show the configuration of bond0.
root@ahv# ovs-appctl bond/show bond0
Output similar to the following is displayed:
---- bond0 ----
bond_mode: active-backup
bond may use recirculation: no, Recirc-ID : -1
bond-hash-basis: 0
updelay: 0 ms
downdelay: 0 ms
lacp_status: off
active slave mac: 0c:c4:7a:48:b2:68(eth0)
slave eth0: enabled
active slave
may_enable: true
slave eth1: disabled
may_enable: false
Hope you like it.. 