Syntax

The syntax is:

curl -k url
curl --insecure url
curl --insecure [options] url
curl --insecure -I url

cURL ignore SSL certificate warnings command

In this example disable certificate verification for curl command:
curl --insecure -I https://202.54.1.2/
OR
curl -k -O https://202.54.1.2/file.tar.gz
Without the -k or --insecure option, you will get an error message that read as follows:

curl: (60) SSL certificate problem: Invalid certificate chain
More details here: https://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
 the bundle, the certificate verification probably failed due to a
 problem with the certificate (it might be expired, or the name might
 not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
 the -k (or --insecure) option.

Here is one useful example where you want to grab a file or see header info from remote host without using SSL enabled SNI domain name:

curl -O --insecure --header 'Host: www.example.com' -I https://207.5.1.10/file.html
### OR ###
curl -k --header 'Host: www.example.com' -I https://207.5.1.10/file.html

Sample outputs:

insecure

Save and close the file. However, I do not recommend disabling SSL checks for all connections by default for security reasons.