There are several reasons why Memcached may fail to start. One common cause is that the configuration file has an error, such as a syntax error or incorrect settings. Another possible cause is that there is not enough memory available for Memcached to run. It could also be due to a port conflict, where another service is already using the port that Memcached is configured to use. Additionally, it could be caused by a permissions issue, where the user running Memcached does not have sufficient privileges to access certain files or directories.
To resolve this issue, you can try several solutions. First, ensure that the configuration file is correct and all settings are valid. You can do this by reviewing the file and correcting any errors manually or by using a tool that checks the syntax of the configuration file for you. Next, check if there is enough memory available for Memcached to run, and adjust the settings accordingly if necessary.
If the issue persists, try changing the port that Memcached uses by updating the configuration file to specify a different port number. Alternatively, check if there are any other services running on the same port and stop them if possible.
Lastly, check the permissions for the user running Memcached and ensure that they have sufficient privileges to access all necessary files and directories. If not, update the permissions accordingly. By following these steps, you should be able to resolve the 'memcached failed to start' error and get Memcached up and running again.