If you have problems with file permissions, the UMASK or UMASK_DIR environment variable might be set incorrectly when mysqld starts. For example, MySQL might issue the following error message when you create a table:

ERROR: Can't find file: 'path/with/filename.frm' (Errcode: 13)

The default UMASK and UMASK_DIR values are 0660 and 0700, respectively. MySQL assumes that the value for UMASK or UMASK_DIR is in octal if it starts with a zero. For example, setting UMASK=0600 is equivalent to UMASK=384 because 0600 octal is 384 decimal.

To change the default UMASK value, start mysqld_safe as follows:

shell> UMASK=384  # = 600 in octal
shell> export UMASK
shell> mysqld_safe &

By default, MySQL creates database directories with an access permission value of 0700. To modify this behavior, set the UMASK_DIR variable. If you set its value, new directories are created with the combined UMASK and UMASK_DIR values. For example, to give group access to all new directories, start mysqld_safe as follows:

shell> UMASK_DIR=504  # = 770 in octal
shell> export UMASK_DIR
shell> mysqld_safe &

For additional details, see Section 4.9, “MySQL Program Environment Variables”.