You may do this using you favorite text editor or by using the command line.
Example:
# Root CA Certificate - AddTrustExternalCARoot.crt
# Intermediate CA Certificate 1 - ComodoRSAAddTrustCA.crt OR ComodoECCAddTrustCA.crt
# Intermediate CA Certificate 2 - ComodoRSADomain/Organization/ExtendedvalidationSecureServerCA.crt OR ComodoRSAECCDomain/Organization/ExtendedvalidationSecureServerCA.crt
# Intermediate CA Certificate 3 - ComodoSHA256SecureServerCA.crt
# Your SSL Certificate - yourDomain.crt
Note: You will not need your SSL certificate for this exercise.
GUI Text Editor
1. Open All files in a text editor. (Remember, not your domain certificate.)
2. Create a new blank text file.
3. Copy contents of all files in reverse order and paste them into the new file.
Example: Intermediate 3, Intermediate 2, Intermediate 1, Root Certificate.
4. Save newly created file as 'yourDomain.ca-bundle'.
Command Line
Linux or UNIX-like Operating Systems:
-- cat ComodoRSAAddTrustCA.crt ComodoRSADomain/Organization/ExtendedvalidationSecureServerCA.crt AddTrustExternalCARoot.crt > yourDomain.ca-bundle
Or
-- cat ComodoSHA256SecureServerCA.crt AddTrustExternalCARoot.crt > yourDomain.ca-bundle
Windows or DOS:
-- copy ComodoRSAAddTrustCA.crt + ComodoRSADomain/Organization/ExtendedvalidationSecureServerCA.crt + AddTrustExternalCARoot.crt yourDomain.ca-bundle
Or
-- copy ComodoSHA256SecureServerCA.crt + AddTrustExternalCARoot.crt yourDomain.ca-bundle
Note: 'yourDomain.ca-bundle' is only a place holder file name. You may call it anything you want.
