{"id":248,"date":"2026-06-18T09:24:10","date_gmt":"2026-06-18T09:24:10","guid":{"rendered":"https:\/\/velanremoteitsupport.com\/blog\/?post_type=techtips&#038;p=248"},"modified":"2026-06-19T05:20:00","modified_gmt":"2026-06-19T05:20:00","slug":"fix-docker-certificate-error-x509-unknown-authority","status":"publish","type":"techtips","link":"https:\/\/velanremoteitsupport.com\/blog\/techtips\/fix-docker-certificate-error-x509-unknown-authority\/","title":{"rendered":"Fixing &#8220;Certificate (X509Error) Signed by Unknown Authority&#8221; in Docker"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\" style=\"font-size:20px\"><strong>What is the X509 error in Docker?<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The error message displayed as \u2018failed to verify certificate: x509: certificate signed by unknown authority\u2019 is related to a certificate validation problem. It appears when Docker cannot verify the SSL\/TLS certificate presented by a Docker registry or server.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:20px\"><strong>The reason for the X509 error:<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">An X509 error occurs when your Docker registry does not have an SSL\/TLS certificate issued by a recognized CA. The self-signed certificates are not fully trusted by default.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">While connecting to a registry, Docker verifies the authenticity of the certificate by searching for the issuer. If it is not found, then Docker blocks access.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:20px\"><strong>How it works<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u00b7&nbsp; &nbsp; &nbsp; &nbsp; A Docker registry presents a self-signed certificate.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u00b7&nbsp; &nbsp; &nbsp; &nbsp; Docker checks its trusted CA store.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u00b7&nbsp; &nbsp; &nbsp; &nbsp; If it failed to find the self-signed certificate there, then Docker rejects the connection and throws an x509 error.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u00b7&nbsp; &nbsp; &nbsp; &nbsp; If you add that certificate to Docker&#8217;s trusted certificate store, Docker will trust it from then on.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u00b7&nbsp; &nbsp; &nbsp; &nbsp; The connection succeeds.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" style=\"font-size:20px\"><strong>How to solve the X509 error. Step-by-step procedure<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Restart Docker so that it can recognize any changes made to the OS certificate. Docker also provides an additional location where you can add an individual registry server CA. Now, to place the CA certificate, follow the below-given steps.<\/p>\n\n\n\n<div class=\"wp-block-columns alignwide is-layout-flex wp-container-core-columns-is-layout-92126d18 wp-block-columns-is-layout-flex\" style=\"margin-bottom:0\">\n<div class=\"wp-block-column has-very-light-gray-to-cyan-bluish-gray-gradient-background has-text-color has-background has-link-color wp-elements-ef94aee1f37ec464c8b9776cf0bf5439 is-layout-flow wp-block-column-is-layout-flow\" style=\"color:#000000;padding-top:2em;padding-right:2em;padding-bottom:2em;padding-left:2em\">\n<p class=\"wp-block-paragraph\"><em>\/etc\/docker\/certs.d\/&lt;docker registry&gt;\/ca.crt<\/em><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The port number should be specified in the image tag, if needed.<\/p>\n\n\n\n<p class=\"has-normal-font-size wp-block-paragraph\" style=\"line-height:1.5\">Example:&nbsp; \/etc\/docker\/certs.d\/my-registry.example.com:5000\/ca.crt<\/p>\n<\/div>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<div class=\"schema-how-to wp-block-yoast-how-to-block\"><p class=\"schema-how-to-description\"><br><span style=\"text-decoration: underline;\">If this method couldn&#8217;t solve the problem, then do the following steps.<br><\/span><\/p> <ol class=\"schema-how-to-steps\"><li class=\"schema-how-to-step\" id=\"how-to-step-1781768399649\"><strong class=\"schema-how-to-step-name\"> Create a file \/etc\/docker\/daemon.json and add insecure-registries<br><\/strong> <p class=\"schema-how-to-step-text\">{<br>\u201cinsecure-registries\u201d : [\u201cdocker.domain.com:443\u201d]<br>}<br><\/p> <\/li><li class=\"schema-how-to-step\" id=\"how-to-step-1781768713061\"><strong class=\"schema-how-to-step-name\">Restart the Docker daemon by executing the command<br><\/strong> <p class=\"schema-how-to-step-text\">systemctl restart docker<br><\/p> <\/li><li class=\"schema-how-to-step\" id=\"how-to-step-1781768740948\"><strong class=\"schema-how-to-step-name\">Make a directory with the same name as the host<br><\/strong> <p class=\"schema-how-to-step-text\">mkdir -p \/etc\/docker\/certs.d\/docker.domain.com<\/p> <\/li><li class=\"schema-how-to-step\" id=\"how-to-step-1781768754763\"><strong class=\"schema-how-to-step-name\">Save the certificate in the newly created directory<\/strong> <p class=\"schema-how-to-step-text\">ex +\u2019\/BEGIN CERTIFICATE\/,\/END CERTIFICATE\/p\u2019 &lt;(echo | OpenSSL s_client -show certs -connect docker.domain.com:443) -suq > \/etc\/docker\/certs.d\/docker.domain.com\/docker_registry.crt<br><\/p> <\/li><li class=\"schema-how-to-step\" id=\"how-to-step-1781768773832\"><strong class=\"schema-how-to-step-name\">Top of Form<br><\/strong> <p class=\"schema-how-to-step-text\"><\/p> <\/li><li class=\"schema-how-to-step\" id=\"how-to-step-1781768787946\"><strong class=\"schema-how-to-step-name\">Bottom of Form<br><\/strong> <p class=\"schema-how-to-step-text\"><\/p> <\/li><\/ol><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" style=\"font-size:20px\"><strong>Need technical support for Docker installation?<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">At Velan, a leading remote IT services provider, we offer expert <strong><a href=\"https:\/\/velanremoteitsupport.com\/docker-consulting-services-solutions-provider\" type=\"link\" id=\"https:\/\/velanremoteitsupport.com\/docker-consulting-services-solutions-provider\">Docker consultation services<\/a><\/strong> for global businesses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Our experienced engineers assist with Docker installation services. Our offerings cover from configuration and troubleshooting to security hardening and ongoing maintenance.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">We ensure quality service (ISO 9001) and strong data security (ISO 27001) in our solutions. As a <a href=\"https:\/\/velanremoteitsupport.com\/\" type=\"link\" id=\"https:\/\/velanremoteitsupport.com\/\"><strong>top outsourced managed IT services company<\/strong><\/a>, we also offer 24\/7 help desk support to help you to efficiently manage your IT environment.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" style=\"font-size:19px\"><strong>Know the answers to the commonly asked questions on Docker certificate errors<\/strong><\/h2>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\"><\/p>\n\n\n\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-1781768974230\"><strong class=\"schema-faq-question\"><strong>What is the use of SSL\/TLS certificates in Docker environments?<\/strong><br><\/strong> <p class=\"schema-faq-answer\">SSL\/TLS certificates confirm that the data is secure when various parts of the Docker environment try to establish a connection. When a client sends a request to the daemon, it must prove itself that it is authorized to perform the requested operation. It is these certificates that authorize clients to access the Docker daemon.<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1781768998199\"><strong class=\"schema-faq-question\"><strong>What are the causes of certificate trust issues in Docker?<\/strong><br><\/strong> <p class=\"schema-faq-answer\">The certificate trust issues in Docker are usually because of this self-signed certificate. Browsers and applications refuse to recognize it as a reliable source. If you want to find out whether a certificate is self-signed or not, look at the issuer field to see if the CA is listed.<br><\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1781769024152\"><strong class=\"schema-faq-question\"><strong>How to disable certificate verification in Docker?<\/strong><br><\/strong> <p class=\"schema-faq-answer\">To skip the verification process of a self-signed certificate, enter the following in the Docker run command:\u00a0<br><br>                                        -e NODE_TLS_REJECT_UNAUTHORIZED=0<br><br><\/p> <\/div> <\/div>\n","protected":false},"excerpt":{"rendered":"<p>What is the X509 error in Docker? The error message displayed as \u2018failed to verify certificate: x509: certificate signed by unknown authority\u2019 is related to a certificate validation problem. It appears when Docker cannot verify the SSL\/TLS certificate presented by a Docker registry or server. The reason for the X509 error: An X509 error occurs [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":264,"comment_status":"open","ping_status":"closed","template":"","meta":{"footnotes":""},"techtips_category":[6],"class_list":["post-248","techtips","type-techtips","status-publish","has-post-thumbnail","hentry","techtips_category-applications"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Quick Fix to Docker Certificate X.509 Signed by Unknown Authority<\/title>\n<meta name=\"description\" content=\"How to resolve the X.509 certificate signed by an unknown authority problem in Docker. Stop Docker registry connection failures.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/velanremoteitsupport.com\/blog\/techtips\/fix-docker-certificate-error-x509-unknown-authority\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Quick Fix to Docker Certificate X.509 Signed by Unknown Authority\" \/>\n<meta property=\"og:description\" content=\"How to resolve the X.509 certificate signed by an unknown authority problem in Docker. 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When a client sends a request to the daemon, it must prove itself that it is authorized to perform the requested operation. It is these certificates that authorize clients to access the Docker daemon.<br>\",\"inLanguage\":\"en-US\"},\"inLanguage\":\"en-US\"},{\"@type\":\"Question\",\"@id\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#faq-question-1781768998199\",\"position\":2,\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#faq-question-1781768998199\",\"name\":\"What are the causes of certificate trust issues in Docker?\",\"answerCount\":1,\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The certificate trust issues in Docker are usually because of this self-signed certificate. Browsers and applications refuse to recognize it as a reliable source. If you want to find out whether a certificate is self-signed or not, look at the issuer field to see if the CA is listed.<br>\",\"inLanguage\":\"en-US\"},\"inLanguage\":\"en-US\"},{\"@type\":\"Question\",\"@id\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#faq-question-1781769024152\",\"position\":3,\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#faq-question-1781769024152\",\"name\":\"How to disable certificate verification in Docker?\",\"answerCount\":1,\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"To skip the verification process of a self-signed certificate, enter the following in the Docker run command:\u00a0<br><br>                                        -e NODE_TLS_REJECT_UNAUTHORIZED=0<br><br>\",\"inLanguage\":\"en-US\"},\"inLanguage\":\"en-US\"},{\"@type\":\"HowTo\",\"@id\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#howto-1\",\"name\":\"Fixing &#8220;Certificate (X509Error) Signed by Unknown Authority&#8221; in Docker\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#article\"},\"description\":\"<br>If this method couldn't solve the problem, then do the following steps.<br>\",\"step\":[{\"@type\":\"HowToStep\",\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#how-to-step-1781768399649\",\"name\":\"Create a file \\\/etc\\\/docker\\\/daemon.json and add insecure-registries\",\"itemListElement\":[{\"@type\":\"HowToDirection\",\"text\":\"{\u201cinsecure-registries\u201d : [\u201cdocker.domain.com:443\u201d]}\"}]},{\"@type\":\"HowToStep\",\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#how-to-step-1781768713061\",\"name\":\"Restart the Docker daemon by executing the command\",\"itemListElement\":[{\"@type\":\"HowToDirection\",\"text\":\"systemctl restart docker\"}]},{\"@type\":\"HowToStep\",\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#how-to-step-1781768740948\",\"name\":\"Make a directory with the same name as the host\",\"itemListElement\":[{\"@type\":\"HowToDirection\",\"text\":\"mkdir -p \\\/etc\\\/docker\\\/certs.d\\\/docker.domain.com\"}]},{\"@type\":\"HowToStep\",\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#how-to-step-1781768754763\",\"name\":\"Save the certificate in the newly created directory\",\"itemListElement\":[{\"@type\":\"HowToDirection\",\"text\":\"ex +\u2019\\\/BEGIN CERTIFICATE\\\/,\\\/END CERTIFICATE\\\/p\u2019  \\\/etc\\\/docker\\\/certs.d\\\/docker.domain.com\\\/docker_registry.crt\"}]},{\"@type\":\"HowToStep\",\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#how-to-step-1781768773832\",\"text\":\"Top of Form\"},{\"@type\":\"HowToStep\",\"url\":\"https:\\\/\\\/velanremoteitsupport.com\\\/blog\\\/techtips\\\/fix-docker-certificate-error-x509-unknown-authority\\\/#how-to-step-1781768787946\",\"text\":\"Bottom of Form\"}],\"inLanguage\":\"en-US\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Quick Fix to Docker Certificate X.509 Signed by Unknown Authority","description":"How to resolve the X.509 certificate signed by an unknown authority problem in Docker. 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