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Create an SPF Record in DNS
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Get the latest tutorials on SysAdmin and open source topics. Hub for Good Supporting each other to make an impact. Write for DigitalOcean You get paid, we donate to tech non-profits. By Justin Ellingwood and Mitchell Anicas. An important part of managing server configuration and infrastructure includes maintaining an easy way to look up network interfaces and IP addresses by name, by setting up a proper Domain Name System DNS. Using fully qualified domain names FQDNs , instead of IP addresses, to specify network addresses eases the configuration of services and applications, and increases the maintainability of configuration files. Setting up your own DNS for your private network is a great way to improve the management of your servers. This provides a central way to manage your internal hostnames and private IP addresses, which is indispensable when your environment expands to more than a few hosts. The CentOS version of this tutorial can be found here.
What are SPF and DKIM Records?
We can send and receive email using a desktop email client. I have seen it used by facebook. Some folks might think that -all will be better as it will reject emails from untrusted hosts. To check if your SPF record is propagated to the public Internet, you can use the dig utility on your Linux box like below. On Ubuntu, you need to install the bind9-dnsutils package in order to use dig command: sudo apt install bind9-dnsutils. Append the following lines at the end of the file. The first line specifies the Postfix policy agent timeout setting. The following lines will impose a restriction on incoming emails by rejecting unauthorized email and checking SPF record. Next time, when you receive an email from a domain that has an SPF record, you can see the SPF check results in the raw email header. The following header indicates the sender sent the email from an authorized host.
A good deal of what is described here can be automated by using the ssh-copy-id command, rather than manually copying and installing public keys. First, you create a git user account and a. Again, the public keys look something like this:. Now, you can set up an empty repository for them by running git init with the --bare option, which initializes the repository without a working directory:. Then, John, Josie, or Jessica can push the first version of their project into that repository by adding it as a remote and pushing up a branch. Note that someone must shell onto the machine and create a bare repository every time you want to add a project. You should note that currently all these users can also log into the server and get a shell as the git user. You can easily restrict the git user account to only Git-related activities with a limited shell tool called git-shell that comes with Git. At this point, users are still able to use SSH port forwarding to access any host the git server is able to reach.