apptainer-verify: add page (#20673)

Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>

pages/linux/apptainer-sign.md

@@ -1,6 +1,7 @@
 # apptainer sign
 
 > Add digital signatures to a SIF container image.
+> See also: `apptainer-verify`.
 > More information: <https://apptainer.org/docs/user/main/cli/apptainer_sign.html>.
 
 - Sign a container image using the default PGP key:

pages/linux/apptainer-verify.md

@@ -0,0 +1,37 @@
+# apptainer verify
+
+> Verify digital signatures of SIF container images.
+> See also: `apptainer-sign`.
+> More information: <https://apptainer.org/docs/user/main/cli/apptainer_verify.html>.
+
+- Verify a container image using the default PGP keyring:
+
+`apptainer verify {{path/to/image.sif}}`
+
+- Verify a container image using a specific public key file:
+
+`apptainer verify --key {{path/to/public.pem}} {{path/to/image.sif}}`
+
+- Verify a container image using a certificate file:
+
+`apptainer verify --certificate {{path/to/certificate.pem}} {{path/to/image.sif}}`
+
+- Verify all objects in the image:
+
+`apptainer verify {{[-a|--all]}} {{path/to/image.sif}}`
+
+- Verify a specific object group within the image:
+
+`apptainer verify {{[-g|--group-id]}} {{group_id}} {{path/to/image.sif}}`
+
+- Verify a specific object by ID within the image:
+
+`apptainer verify {{[-i|--sif-id]}} {{object_id}} {{path/to/image.sif}}`
+
+- Output verification results in JSON format:
+
+`apptainer verify {{[-j|--json]}} {{path/to/image.sif}}`
+
+- Display help:
+
+`apptainer verify {{[-h|--help]}}`