Mail Basics — about MX records, A records, TXT records etc

CF. MainEnable Setup
Prerequisites >>
- install software on a Master Server
- Need A record of mail.Master Server
- Need MX record of mail.Master Server
- IIS needs to route traffic to the Master Server (for web console client)

Attaching EFS to Rocket Chat or MongoDB instance
1. Beware of the Security groups
2. Install yum install nfs-utils (to mount via nfs)
- you can mount via nfs, efs helper(DNS), or by IP
3. execute command mount -t nfs4 -o XXXXX:/ /where/you/want/to/mount(inlocal)
- to unmount umount /where/you/mounted/on/local

First Create Active Directory in AWS
- (type in like a domain name)
- 2 Availability zones

Create Master Server EC2

AWS Secrets Manager
→ create the key — could be RDS, DynamoDB, or custom
→ Put in any <key> <value> pair

How to access :
1. via program code ex. require(aws)
2. via CLI command line
this will output a JSON format of file

Cache vs Artifacts


Standard process
git status
git add .
git commit -m “new change”
git push [repository name]

How to push to branch
git status
lets you check which branch you’re on
git branch OR git branch --list
git branch june
git checkout june

How to pull ONLY a branch repo
git clone -b june <repo url>

If there is no “REMOTE” repository but have “local” repository
will get error that there is no upstream branch
git push --set-upstream origin[repositoryname] june

How to check origin (=remote branch)
git remote -v
git remote set-url origin new.git.url/here

When your instance failes to create
— Because they failed to create specific resources (security group, route53)
— Because the success health check signal didn’t come through for a certain time → This doesn’t give you much info about error
(Mostly because of Metadata(cfn-init) or UserData)

Then How should we Troubleshoot?
* Turn Off the “roll back function
- So we can go into the instance to troubleshoot
→ ‘Stack Creation Option’ : Rollback — disable (When launching template)

Then SSH into instance and Check — Metadata, Userdata, etc
* /var/log/cfn-init.log
* Check User Data Script : cat /var/lib/cloud/instance/scripts/part-001

June Chung

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