cannot create temp file for here-document: No space left on device

When I accessed one of my EC2 instances, I found this sentence on my terminal:

cannot create temp file for here-document: No space left on device

This did not stop my instance working, but this might bother you (like me) 😒 To solve a problem, we need to find its main cause. In my case, my instance runs cron jobs almost every minute to support jasan.io, and it is likely that its origin is related to mail that has been created after finishing cron job.

First of all, check the size of directories and files in the instance by entering

sudo du -x / | sort -n | tail -40

If it does not give clear information, enter

sudo find / -type f -printf '%12s %p\n' 2>/dev/null|awk '{if($1>999999999)print $0;}'

If the memory was running out because of mails, it is likely that you would see a very big number like the below:

140737477885952 /proc/kcore
  5466297384 /var/spool/mail/ec2-user

Since mails were stored in /var/spool/mail/ec2-user, delete mails by entering the following command:

cat /dev/null > /var/spool/mail/ec2-user

References

Does /var/spool/mail/user ever get cleared?

xvda1 is 100% full, What is it? how to fix?

Tab completion errors: bash: cannot create temp file for here-document: No space left on device

Delete cron mails