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update(8) [v7 man page]

UPDATE(8)						      System Manager's Manual							 UPDATE(8)

update - periodically update the super block SYNOPSIS
/etc/update DESCRIPTION
Update is a program that executes the sync(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(1), init(8) BUGS
With update running, if the CPU is halted just as the sync is executed, a file system can be damaged. This is partially due to DEC hard- ware that writes zeros when NPR requests fail. A fix would be to have sync(1) temporarily increment the system time by at least 30 seconds to trigger the execution of update. This would give 30 seconds grace to halt the CPU. UPDATE(8)

Check Out this Related Man Page

sync(2) 							   System Calls 							   sync(2)

sync - update super block SYNOPSIS
#include <unistd.h> void sync(void); DESCRIPTION
The sync() function writes all information in memory that should be on disk, including modified super blocks, modified inodes, and delayed block I/O. Unlike fsync(3C), which completes the writing before it returns, sync() schedules but does not necessarily complete the writing before returning. USAGE
The sync() function should be used by applications that examine a file system, such as fsck(1M), and df(1M), and is mandatory before rebooting. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
df(1M), fsck(1M), fsync(3C), attributes(5), standards(5) SunOS 5.11 5 Jul 1990 sync(2)
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