The command that updates the database used by the locate command is 'updatedb'. This command is specifically designed for this purpose and does not require any path or parameters.

The command mount --bind makes the contents of one directory available in another directory. It allows you to create another access point to the same file system data without moving the actual contents. This command is particularly useful for accessing data from multiple locations or for creating specific directory structures needed for different applications without duplicating the data.

To create a new file that shares the same inode number as an existing file, a hard link must be created to the original file. The command for creating a hard link is 'ln <original_file> <new_file>'. In this case, 'ln a.txt c.txt' will create a hard link named c.txt that shares the inode number 525385 with a.txt, since it links directly to the same data on disk.

To ensure new files created within the directory 'sales' are owned by the group 'sales', you can use 'chmod g+s sales' and 'chmod 2775 sales'. The command 'chmod g+s sales' sets the group ID on the directory, so files created inside will inherit the group ownership. The command 'chmod 2775 sales' sets the permissions explicitly, ensuring the setgid bit is applied, which also ensures new files inherit the directory's group ownership.

To display all currently mounted filesystems, the commands 'cat /proc/self/mounts' and 'mount' can be used. The file '/proc/self/mounts' contains detailed information about mounted filesystems and can be viewed using the 'cat' command. The 'mount' command, when used without arguments, lists all mounted filesystems. Other options either do not provide information about mounted filesystems or do not exist.