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Check whether a certificate expires within the next days

harmless rootSSL and certificatesalle
Adjust the values, the command updates live
root@server
openssl x509 -in /etc/letsencrypt/live/example.com/cert.pem -noout -checkend $(( 30 * 86400 )) && echo "noch gültig" || echo "läuft bald ab"

The -checkend option expects seconds and returns exit code 0 if the certificate is still valid after that time, otherwise 1. The $(( ... )) arithmetic converts days into seconds. This makes it easy to trigger a warning in scripts or cron jobs before visitors see an error message.

Note: Root is only needed for protected paths like /etc/letsencrypt/.

Also searched as

  • check if certificate expires in 30 days
  • monitor ssl expiry with cron
  • openssl checkend script
  • certificate expiration warning script

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All in SSL and certificates

Check the SSL certificate expiration date of a website

$openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -dates
harmlessSSL and certificates

Show the expiry date and subject of a certificate file

#openssl x509 -in /etc/letsencrypt/live/example.com/cert.pem -noout -subject -issuer -enddate
harmlessSSL and certificates

Check whether a private key matches a certificate

#openssl x509 -noout -modulus -in /etc/ssl/certs/example.com.crt | openssl md5 && openssl rsa -noout -modulus -in /etc/ssl/private/example.com.key | openssl md5
harmlessSSL and certificates

Check whether a website's certificate is trusted

$openssl s_client -connect example.com:443 -servername example.com -verify_hostname example.com </dev/null 2>/dev/null | grep "Verify return code"
harmlessSSL and certificates

Create a self-signed certificate for testing

$openssl req -x509 -newkey rsa:2048 -nodes -days 365 -keyout test.key -out test.crt -subj "/CN=test.example.com" -addext "subjectAltName=DNS:test.example.com"
cautionSSL and certificates

Read all domains of a certificate (SAN)

$openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -ext subjectAltName
harmlessSSL and certificates

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