rlim_fd_max

Description

Specifies the “hard” limit on file descriptors that a single process might have open. Overriding this limit requires superuser privilege.

Data Type

Signed integer

Default

65,536

Range

1 to MAXINT

Units

File descriptors

Dynamic?

No

Validation

None

When to Change

When the maximum number of open files for a process is not enough. Other limitations in system facilities can mean that a larger number of file descriptors is not as useful as it might be. For example:

• A 32-bit program using standard I/O is limited to 256 file descriptors. A 64-bit program using standard I/O can use up to 2 billion descriptors. Specifically, standard I/O refers to the stdio (3C) functions in libc (3LIB) .

• select is by default limited to 1024 descriptors per fd_set. For more information, see select (3C) . A 32-bit application code can be recompiled with a larger fd_set size (less than or equal to 65,536). A 64-bit application uses an fd_set size of 65,536, which cannot be changed.

An alternative to changing this on a system wide basis is to use the plimit (1) command. If a parent process has its limits changed by plimit, all children inherit the increased limit. This alternative is useful for daemons such as inetd.

Commitment Level

Unstable