mysqldump: Got errno 28 on write
Solution 1:
Error Message
Backup failed: mysqldump: Got errno 28 on write
Meaning
Insufficient disk space to store output.
Solution
Free up some disk space. You might want to track down the reason you're low on disk space too.
Source: https://sittinginoblivion.com/wiki/backup-failed-mysqldump-got-errno-28-write
Solution 2:
I got the same error but it turned out that there was no memory left to accommodate a new file. Removing unwanted files to free up the space for new (*.sql) file helped.
P.S: You can see your memory consumption by the command: df -h.