1.Obtain an SSL certificate ( Let's Encrypt )
Install the latest open ssl
# dnf -y install openssl-devel
1.1 advance preparation
1.Package management system Snappy installed
Since the SSL certificate issuing tool "certbot" of Let's Encrypt is recommended to be installed using "snap" after 2021, install Snapd first.(Can also be installed the traditional way with dnf or yum)
# dnf upgrade
# dnf -y install snapd
Enable systemd unit to manage the main snap communication socket
# systemctl enable --now snapd.socket
Enable Classics Snap support
# ln -s /var/lib/snapd/snap /snap
Version Check
# snap --version
snap 2.77.1-0.fc45
snapd 2.77.1-0.fc45
series 16
fedora 45
kernel 7.2.11-300.fc45.x86_64
architecture amd6
Log out and log in again or reboot the system to ensure that the snap path is updated correctly
2.certbot package install
# snap install --classic certbot
certbot 5.9.0 from Certbot Project (certbot-eff✓) installed
Create symbolic link to /snap/bin/certbot
# ln -s /snap/bin/certbot /usr/bin/certbot
Confirmation
# ls -la /usr/bin/certbot
lrwxrwxrwx 1 root root 17 Nov 3 13:17 /usr/bin/certbot -> /snap/bin/certbot
# ls -la /snap/bin/certbot
lrwxrwxrwx 1 root root 13 Nov 3 13:17 /snap/bin/certbot -> /usr/bin/snap
1.2 Obtaining Certificates
# certbot certonly --webroot -w /var/www/html/[FQDN] -d [FQDN]
Registration of e-mail address and agreement to terms of use are required for the first time only.
Specify an email address to receive
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Enter email address or hit Enter to skip.
(Enter 'c' to cancel): [mail address]
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Please read the Terms of Service at:
https://letsencrypt.org/documents/LE-SA-v1.8-July-06-2026.pdf
You must agree in order to register with the ACME server. Do you agree?
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(Y)es/(N)o: y
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Would you be willing, once your first certificate is successfully issued, to
share your email address with the Electronic Frontier Foundation, a founding
partner of the Let's Encrypt project and the non-profit organization that
develops Certbot? We'd like to send you email about our work encrypting the web,
EFF news, campaigns, and ways to support digital freedom.
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(Y)es/(N)o: y
Account registered.
Requesting a certificate for [FQDN]
Successfully received certificate.
Certificate is saved at: /etc/letsencrypt/live/[FQDN]/fullchain.pem
Key is saved at: /etc/letsencrypt/live/[FQDN]/privkey.pem
This certificate expires on 2027-02-07.
These files will be updated when the certificate renews.
Certbot has set up a scheduled task to automatically renew this certificate in the background.
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If you like Certbot, please consider supporting our work by:
* Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
* Donating to EFF: https://eff.org/donate-le
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Success if displayed"Successfully received certificate".
# The following certificate is obtained under [/etc/letsencrypt/live/[FQDN]/] as described in the message
# cert.pem ⇒ SSL server certificate (including public key)
# chain.pem ⇒ intermediate certificate
# fullchain.pem ⇒ File containing cert.pem and chain.pem combined
# privkey.pem ⇒ private key
It is a prerequisite that the server on which the work is to be performed is accessible from the Internet at port 80.
FQDN (Fully Qualified Domain Name) :Hostname. Domain name without abbreviation
If there are multiple FQDNs for which you want to obtain certificates, specify multiple -d [FQDNs] for which you want to obtain certificates
Renewing certificates already obtained
# Renew all certificates with an expiration date of less than 30 days
# If you want to renew regardless of the number of days remaining on the expiration date, specify [--force-renewal] as well.
# certbot [--force-renewal] renew
Saving debug log to /var/log/letsencrypt/letsencrypt.log
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Processing /etc/letsencrypt/renewal/[FQDN].conf
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Renewing an existing certificate for [FQDN]
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Congratulations, all renewals succeeded:
/etc/letsencrypt/live/[FQDN]/fullchain.pem (success)
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1.2 Automatic renewal of certificates(Let's Encrypt)
①Pre-registration testing
First, test the automatic update using the following --dry-run option.
With this option, certificates are not renewed, only checked, so there is no need to worry about getting stuck with a limit on the number of times a certificate can be obtained.
# certbot renew --dry-run
Saving debug log to /var/log/letsencrypt/letsencrypt.log
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Processing /etc/letsencrypt/renewal/[FQDN].conf
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Account registered.
Simulating renewal of an existing certificate for[FQDN]
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Congratulations, all simulated renewals succeeded:
/etc/letsencrypt/live/fedora.korodes.com/fullchain.pem (success)
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②When you install the snap version of certbot, the automatic certificate renewal function is also installed.
# systemctl list-timers | less
NEXT LEFT LAST PASSED UNIT ACTIVATES
Mon 2026-11-09 15:07:39 JST 28min Mon 2026-11-09 14:10:10 JST 29min ago fwupd-refresh.timer fwupd-refresh.service
Mon 2026-11-09 17:01:38 JST 2h 22min Mon 2026-11-09 13:35:12 JST 1h 4min ago dnf-makecache.timer dnf-makecache.service
Tue 2026-11-10 00:00:00 JST 9h - - sa-update.timer sa-update.service
Tue 2026-11-10 00:05:34 JST 9h Mon 2026-11-09 13:22:22 JST 1h 17min ago logrotate.timer logrotate.service
Tue 2026-11-10 00:05:42 JST 9h Mon 2026-11-09 13:35:02 JST 1h 4min ago plocate-updatedb.timer plocate-updatedb.service
Tue 2026-11-10 02:59:00 JST 12h - - snap.certbot.renew.timer snap.certbot.renew.service
Tue 2026-11-10 13:12:22 JST 22h Mon 2026-11-09 13:12:22 JST 1h 27min ago systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.service
Sun 2026-11-15 01:00:00 JST 5 days Sun 2026-11-08 10:03:54 JST - raid-check.timer raid-check.service
Mon 2026-11-16 00:29:20 JST 6 days Mon 2026-11-09 13:35:12 JST 1h 4min ago fstrim.timer fstrim.service
9 timers listed.
Pass --all to see loaded but inactive timers, too.
snap.certbot.renew.timer is registered
Check the unit file snap.certbot.renew.timer
# vi /etc/systemd/system/snap.certbot.renew.timer
[Unit]
# Auto-generated, DO NOT EDIT
Description=Timer renew for snap application certbot.renew
Requires=var-lib-snapd-snap-certbot-5911.mount
After=var-lib-snapd-snap-certbot-5911.mount
X-Snappy=yes
[Timer]
Unit=snap.certbot.renew.service
OnCalendar=*-*-* 02:59
OnCalendar=*-*-* 13:03
[Install]
WantedBy=timers.target
According to the above configuration, it will attempt to update at 02:59 and 13:03 every day as specified in the OnCalender parameter(However, the set time changes randomly with each update)
Check the unit file snap.certbot.renew.service
# vi /etc/systemd/system/snap.certbot.renew.service
[Unit]
# Auto-generated, DO NOT EDIT
Description=Service for snap application certbot.renew
Requires=var-lib-snapd-snap-certbot-5911.mount
Wants=network.target
After=var-lib-snapd-snap-certbot-5911.mount network.target snapd.apparmor.service
X-Snappy=yes
[Service]
EnvironmentFile=-/etc/environment
ExecStart=/usr/bin/snap run --timer="00:00~24:00/2" certbot.renew
SyslogIdentifier=certbot.renew
Restart=no
WorkingDirectory=/var/snap/certbot/5911
TimeoutStopSec=30s
Type=oneshot
However, the web server using the certificate will not be restarted, so set up a script to run automatically after the update
# vi /etc/letsencrypt/renewal-hooks/post/web_restart.sh
The following content is described
#!/bin/bash
systemctl reload httpd
# chmod 755 /etc/letsencrypt/renewal-hooks/post/web_restart.sh
2. Converting Apache to https
Install the following just in case
# dnf -y install mod_ssl
2.1 Edit ssl.conf file
# vi /etc/httpd/conf.d/ssl.conf
Line 59 : Uncomment and change
DocumentRoot "/var/www/html/[FQDN]"
Line 60 : Uncomment and change
ServerName [FQDN]:443
Line 101 : Make it a comment and add it below
# SSLCertificateFile /etc/pki/tls/certs/localhost.crt
SSLCertificateFile /etc/letsencrypt/live/[FQDN]/cert.pem
Line 109 : Make it a comment and add it below
# SSLCertificateKeyFile /etc/pki/tls/private/localhost.key
SSLCertificateKeyFile /etc/letsencrypt/live/[FQDN]/privkey.pem
Line 119 : Add
SSLCertificateChainFile /etc/letsencrypt/live/[FQDN]/chain.pem
Restart Apache.
# systemctl restart httpd
Allow https in Firewall
# firewall-cmd --add-service=https --permanent
success
# firewall-cmd --reload
success
2.2 Redirect HTTP communications to HTTPS
Add the following to the virtual host configuration file
# vi /etc/httpd/conf.d/vhost.conf
<VirtualHost *:80>
RewriteEngine On ←Add
RewriteCond %{HTTPS} off ←Add
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L] ←Add
DocumentRoot /var/www/html/[FQDN].com
ServerName [FQDN]
ServerAdmin [mail address]
ErrorLog logs/[FQDN].com.error_log
CustomLog logs/[FQDN].access_log combined
</VirtualHost>
<Directory "/var/www/html/[FQDN]">
Options FollowSymLinks
AllowOverride All
</Directory>
Restart Apache
# systemctl restart httpd
3. SSL/TLS (Let's Encrypt) settings on the mail server
3.1 Obtaining a certificate for the mail server
Stop the web server once and then do it
# systemctl stop httpd.service
# certbot certonly --standalone -d mail.[domain]
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Requesting a certificate for mail.[domain]
Successfully received certificate.
Certificate is saved at: /etc/letsencrypt/live/mail.[domain]/fullchain.pem
Key is saved at: /etc/letsencrypt/live/mail.[domain]/privkey.pem
This certificate expires on 2027-02-07.
These files will be updated when the certificate renews.
Certbot has set up a scheduled task to automatically renew this certificate in the background.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
If you like Certbot, please consider supporting our work by:
* Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
* Donating to EFF: https://eff.org/donate-le
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3.2 Postfix Configuration
# vi /etc/postfix/main.cf
Per Line726, 732: comment
#smtpd_tls_cert_file = /etc/pki/tls/certs/postfix.pem
#smtpd_tls_key_file = /etc/pki/tls/private/postfix.key
Add to the last line
smtpd_use_tls = yes
smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_cert_file = /etc/letsencrypt/live/mail.[domain]/fullchain.pem
smtpd_tls_key_file = /etc/letsencrypt/live/mail.[domain]/privkey.pem
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
# vi /etc/postfix/master.cf
Line 19,20,22,23 : Uncomment
submission inet n - n - - smtpd
-o syslog_name=postfix/submission
# -o smtpd_forbid_unauth_pipelining=n
-o smtpd_tls_security_level=encrypt
-o smtpd_sasl_auth_enable=yes
Line 40,41,43,44 : Uncomment
submissions inet n - n - - smtpd
-o syslog_name=postfix/smtps
# -o smtpd_forbid_unauth_pipelining=no
-o smtpd_tls_wrappermode=yes
-o smtpd_sasl_auth_enable=yes
3.3 Dovecot Settings
# vi /etc/dovecot/dovecot.conf
Per Line 48：Change
ssl = yes
Pwe Line 52,53：Commented out and added certificate/key file specification below
#cert_file = /etc/pki/dovecot/certs/dovecot.pem
#key_file = /etc/pki/dovecot/private/dovecot.pem
ssl_server_cert_file = /etc/letsencrypt/live/mail.[domain]/fullchain.pem
ssl_server_key_file = /etc/letsencrypt/live/mail.[domain]/privkey.pem
Allow Port 587 in firewall
# firewall-cmd --add-port=587/tcp --permanent
# firewall-cmd --reload
Restart
# systemctl restart postfix dovecot
3.4 Thunderbird Settings
Receiving servers
Port : 143
Connection security : STARTTLS
Authentication method : Normal password
Sending server
Port : 587
Connection security : STARTTLS
Authentication method : Normal password
