vault backup: 2026-02-25 16:53:37

2026-02-25 16:53:37 +08:00
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+---
+page-title: "How do I install a root certificate? - Ask Ubuntu"
+url: https://askubuntu.com/questions/73287/how-do-i-install-a-root-certificate
+date: "2023-03-30 16:38:30"
+---
+
+[
+
+![Sparky1's user avatar](https://www.gravatar.com/avatar/6165bb851740276122c7ba3bf5310906?s=64&d=identicon&r=PG)
+
+](https://askubuntu.com/users/31155/sparky1)
+
+4
+
+Given a CA certificate file `foo.crt`, follow these steps to install it on Ubuntu:
+
+1.  Create a directory for extra CA certificates in `/usr/local/share/ca-certificates`:
+    
+    ```
+    sudo mkdir /usr/local/share/ca-certificates/extra
+    ```
+    
+2.  Copy the CA `.crt` file to this directory:
+    
+    ```
+    sudo cp foo.crt /usr/local/share/ca-certificates/extra/foo.crt
+    ```
+    
+3.  Let Ubuntu add the `.crt` file's path relative to `/usr/local/share/ca-certificates` to `/etc/ca-certificates.conf`:
+    
+    ```
+    sudo dpkg-reconfigure ca-certificates
+    ```
+    
+    To do this non-interactively, run:
+    
+    ```
+    sudo update-ca-certificates
+    ```
+    
+
+In case of a `.pem` file on Ubuntu, it must first be converted to a `.crt` file:
+
+```
+openssl x509 -in foo.pem -inform PEM -out foo.crt
+```
+
+Or a `.cer` file can be converted to a `.crt` file:
+
+```
+openssl x509 -inform DER -in foo.cer -out foo.crt
+```
+
+[
+
+![BeastOfCaerbannog's user avatar](https://i.stack.imgur.com/IRB44.jpg?s=64&g=1)
+
+](https://askubuntu.com/users/618353/beastofcaerbannog)
+
+answered Jan 12, 2012 at 12:37
+