OhSudo — new Security articlesNew Security articles from OhSudo: practical fixes for DevOps engineers, SysAdmins and IT folks.https://ohsudo.com/en-us"Certificate has expired": check the dates, renew it, and find out why it didn't renewhttps://ohsudo.com/articles/ssl-certificate-has-expired/https://ohsudo.com/articles/ssl-certificate-has-expired/Fix "certificate has expired" and NET::ERR_CERT_DATE_INVALID: check the dates with openssl, renew with Certbot, reload the server, and fix why renewal or clock failed.Mon, 09 Nov 2026 00:00:00 GMTSecuritytlssslcertbotopensslnginxtroubleshootingcontact@ohsudo.com (OhSudo)Certbot "failed to authenticate some domains": read the Type, then fix DNS, port 80 or the pathhttps://ohsudo.com/articles/certbot-failed-to-authenticate-some-domains/https://ohsudo.com/articles/certbot-failed-to-authenticate-some-domains/Fix Certbot "failed to authenticate some domains": read the error type, then fix DNS records, an IPv6 AAAA record, a closed port 80, the webroot, Cloudflare and CAA.Thu, 05 Nov 2026 00:00:00 GMTSecuritycertbotlets-encrypttlsnginxdnstroubleshootingcontact@ohsudo.com (OhSudo)JWT "jwt expired" and "invalid signature": how to find out what is wrong with a tokenhttps://ohsudo.com/articles/jwt-expired-invalid-signature/https://ohsudo.com/articles/jwt-expired-invalid-signature/Fix JWT "jwt expired" and "invalid signature": read the exp claim, check clock differences, the secret, HS256 vs RS256 and rotated keys, without turning verification off.Thu, 05 Nov 2026 00:00:00 GMTSecurityjwtauthenticationnodejspythonapitroubleshootingcontact@ohsudo.com (OhSudo)SSH "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!": check it, then fix known_hostshttps://ohsudo.com/articles/ssh-remote-host-identification-has-changed/https://ohsudo.com/articles/ssh-remote-host-identification-has-changed/Fix the SSH host key warning safely: find out why the key changed, verify the new fingerprint on the server, then remove the old key with ssh-keygen -R.Mon, 02 Nov 2026 00:00:00 GMTSecuritysshopensshknown-hostshost-keyssecuritytroubleshootingcontact@ohsudo.com (OhSudo)"SSL certificate problem: unable to get local issuer certificate": fix the chain, not the checkhttps://ohsudo.com/articles/ssl-certificate-problem-unable-to-get-local-issuer-certificate/https://ohsudo.com/articles/ssl-certificate-problem-unable-to-get-local-issuer-certificate/Fix "unable to get local issuer certificate" in curl, git, pip, npm and Docker: find the broken link with openssl, then fix the server chain or add the missing CA.Mon, 02 Nov 2026 00:00:00 GMTSecuritytlssslcertificatescurlgitpipnodejstroubleshootingcontact@ohsudo.com (OhSudo)