How to fix Nextcloud updater PHP Fatal error:  Allowed memory size of ... bytes exhausted

Problem:

While trying to update Nextcloud using the command line (e.g. SSH) using a command like

php updater/updater.phar

you see an error message containing PHP Fatal error:  Allowed memory size of ... bytes exhausted such as this one:

[✔] Check for expected files
[✔] Check for write permissions
[✔] Create backup
[✔] Downloading
[ ] Verify integrity ...PHP Fatal error:  Allowed memory size of 134217728 bytes exhausted (tried to allocate 155061456 bytes) in phar:///owncloud.mydomain.com/updater/updater.phar/lib/Updater.php on line 637

Solution

First, try to adjust the memory limit in your webhosting panel or php.ini. If this is not possible - such as for my hoster, which has different settings for the FastCGI PHP as opposed to the command line (CLI) PHP, you can manually set the memory limit using

php -d memory_limit=512M updater/updater.phar