4.3BSD-UWisc/man/cat8/update.8

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UPDATE(8)           UNIX Programmer's Manual            UPDATE(8)



NAME
     update - periodically update the super block

SYNOPSIS
     /etc/update

DESCRIPTION
     _U_p_d_a_t_e is a program that executes the _s_y_n_c(2) primitive
     every 30 seconds.  This insures that the file system is
     fairly up to date in case of a crash.  This command should
     not be executed directly, but should be executed out of the
     initialization shell command file.

SEE ALSO
     sync(2), sync(8), init(8), rc(8)

BUGS
     With _u_p_d_a_t_e running, if the CPU is halted just as the _s_y_n_c
     is executed, a file system can be damaged.  This is par-
     tially due to DEC hardware that writes zeros when NPR
     requests fail.  A fix would be to have _s_y_n_c(8) temporarily
     increment the system time by at least 30 seconds to trigger
     the execution of _u_p_d_a_t_e. This would give 30 seconds grace to
     halt the CPU.































Printed 12/27/86         April 27, 1985                         1