Uly.me

cloud engineer

Adding Domains in Certbot

You can register multiple domains to a single SSL certificate. This is particularly useful if you are hosting multiple domains on one server. This command adds more domains to your existing certificate.

certbot --expand -d existing.com -d newdomain1.com -d newdomain2.com

Check if the domains were added.

certbot certificates

Certbot certificates are valid for 90 days, but they automatically renew themselves if expiration is less than 30 days. If you need to renew manually for some odd reason, you can run this command. You can also perform a dry-run before renewing.

certbot renew
certbot renew --dry-run

Change DNS Records in Route 53 via CLI

How to change DNS records in Route 53 via AWS CLI.

  • Assuming AWS CLI is already configured
  • Uses Route53 change-resource-record-sets to update DNS records
  • Substitute with your own hosted-zone-id
  • Uses JSON files containing record sets
  • See JSON file examples below 
cd /path/to/scripts/
# the command to switch to the elb
aws route53 change-resource-record-sets --hosted-zone-id xxxxxxxxxxxxxx --change-batch file://elb.json
# the command to switch to standard site
aws route53 change-resource-record-sets --hosted-zone-id xxxxxxxxxxxxxx --change-batch file://live.json

elb.json = points to AWS ELB (elastic load balancer)

{
   "Comment": "back to elb",
   "Changes": [
      {
         "Action": "UPSERT",
         "ResourceRecordSet": {
            "Name": "yourdomain.com",
            "Type": "A",
            "AliasTarget": {
               "HostedZoneId": "xxxxxxxxxxxxxx",
               "EvaluateTargetHealth": false,
               "DNSName": "xxxxxxxxxxxxx.us-east-1.elb.amazonaws.com."
            }
         }
      }
   ]
}

live.json = points to your standard site. Value is your IP Address.

{
   "Comment": "back to live",
   "Changes": [
      {
         "Action": "UPSERT",
         "ResourceRecordSet": {
            "Name": "yourdomain.com",
            "Type": "A",
            "TTL": 60,
            "ResourceRecords": [
               {
                  "Value": "xxx.xxx.xxx.xxx"
               }
            ]
         }
      }
   ]
}

Domain Sorter

Here’s a Bash and Perl script for sorting domains and subdomains.

Command:

$ cat filename | perl -ple'$_=join".",reverse split/\./' | sort | perl -ple'$_=join".",reverse split/\./'

What’s in the domains.txt?

$ cat domains.txt
domain.com
abc.com
xyz.com
bbb.com
mail.gmail.com
ess.sfss.org
csub.edu
gmail.com

Result:

$ cat domains.txt | perl -ple'$_=join".",reverse split/\./' | sort | perl -ple'$_=join".",reverse split/\./'
abc.com
bbb.com
domain.com
gmail.com
mail.gmail.com
xyz.com
csub.edu
ess.sfss.org

You can also pipe the result to another file.

$ cat filename | perl -ple'$_=join".",reverse split/\./' | sort | perl -ple'$_=join".",reverse split/\./' > output.txt

Source.