If Redis encounters an error stating it cannot open the log file, it is often related to file permisssions. This issue can occur after accidental deleting the Redis folder under the /var directory and attempting to restart Redis. When executing the command to start the service:

/etc/init.d/redis-server start

The system returns the following error:

Starting redis-server:
*** FATAL CONFIG FILE ERROR ***
Reading the configuration file, at line 94
>>> 'logfile /var/log/redis/redis-server.log'
Can't open the log file: No such file or directory
failed

In this case, the eror indicates that the referenced log file path doesn't exist anymore. To resolve this, you can recreate the log file:

touch /var/log/redis/redis-server.log

However, upon restarting the Redis server again, enother error might occur:

Starting redis-server:
*** FATAL CONFIG FILE ERROR ***
Reading the configuration file, at line 94
>>> 'logfile /var/log/redis/redis-server.log'
Can't open the log file: Permission denied
failed

This message points to a permissions issue with the newly created log file. To investigate further, check the permissions on the log file using:

ls -l /var/log/redis/redis-server.log

The output may resemble:

-rw-r--r-- 1 root root 0 Jun 2 10:05 /var/log/redis/redis-server.log

Here, the file is owned by root, and Redis might not have adequate permissions to write to it. To fix this, modify the file permissions by running:

chmod 777 /var/log/redis/redis-server.log

After adjusting the permissions, restart the Redis server again:

/etc/init.d/redis-server start

This should resolve the issue and allow Redis to start successfully.