I went to adjust the APC cache size on one of my Ubuntu 10.04 LTS (Lucid) servers today. This particular server runs a single app, and it only uses 12M of cache, so I wanted to change the cache size from the default 32M to 16M. I put
/etc/php5/conf.d/apc.ini and restarted Apache… and to my surprise, Apache didn’t come back up. I found this error in the error log:
Which (via Google) led me to this very thorough blog post.
TL;DR, for older versions of APC like the version that ships with Ubuntu 10.04 LTS (APC version 3.1.3p1), you cannot use the “M” suffix. The correct syntax is
According to this bug report, it looks like APC >= 3.1.4 expects the M/G suffix, so this shouldn’t be an issue with Ubuntu 12.04 LTS (Precise).