On Thu, 2022-08-11 at 21:42 -0600, home user wrote: > I installed sendmail-doc and read the "WHO AM I" section of README.cf. > It says gethostname is called to get the host name, then the result of > that is sent to "gethostbyname" to get the fully qualified domain name. > My C/C++ skills are very rusty and out-of-date, but I succeeded in > writing a C++ program to see what's going on. It took a while! The > hostname returned by gethostname is correct. But the h_name returned by > gethostbyname is the same as what was returned by gethostname. It was > not a fully qualified domain name. > > I'm no sys.admin. I do not understand what the "WHO AM I" section of > README.cf is saying to do in this situation. HELP! > > By the way, I was able to use mailx to send a test message from me (a > regular user) to root, and root received the message properly. Also, I > only use mailx for messages from rkhunter and gsmartcontrol. If you're only using mail internally, and messages are coming through, it probably doesn't matter about the warning. And I thought the defaults for sendmail only worked with localhost, anyway (requiring you to intervene with manual configuration to be less secure). If you want to send mail to the outside world through it, you'd need to configure everything correctly. My previous experiments with sendmail and its documentation determined that it *discovers* its addressing. It knows its IP, it does a reverse DNS query to find the hostname for that IP, and it confirms back in the other direction (asks what IP belongs to that hostname). It wants the same answer in both directions. i.e. If it were on 192.168.1.1 and does a reverse search to find its hostname (example.com), doing a forward search for the IP for example.com needs to return the same 192.168.1.1 IP address. It doesn't have to query a DNS server for that, it can use the info in your /etc/hosts file. Again, if you're only doing internal mail, just ensure that you have the minimum of this in /etc/hosts: 127.0.0.1 localhost localhost.localdomain ::1 localhost localhost.localdomain Don't put actual hostnames in with those loopback addresses. If you do want hostnames in /etc/hosts file (e.g. for local machines), they should be separate, like this: 192.168.1.1 example.com example The actual interface IP address, then the desired full address for that interface, and then any aliases you want to use can be listed after. When something consults the /etc/hosts file to find the name for the IP, the first name is returned. Whem something consults the /etc/hosts file to find the IP for a hostname, any name right of the IP matches. If your server is DHCP managed, set the DHCP server to always give it the same addresses. -- uname -rsvp Linux 3.10.0-1160.71.1.el7.x86_64 #1 SMP Tue Jun 28 15:37:28 UTC 2022 x86_64 Boilerplate: All unexpected mail to my mailbox is automatically deleted. I will only get to see the messages that are posted to the mailing list. _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
