update linux command

update

update [options]

System administration command. update is a daemon that controls how often the kernel's disk buffers are flushed to disk. update is also known as bdflush. The daemon forks a couple of processes to call system functions flush() and sync(). When called by an unprivileged user, no daemon is created. Instead, update calls sync() and then exits. By default, update will wake up every 5 seconds and flush() some dirty buffers. If that doesn't work, it will try waking up every 30 seconds to sync() the buffers to disk. Not all of the listed options are available in every version of update.

Options

-d

Display the kernel parameters. This does not start the update daemon.

-f seconds

Call flush() at this interval. Default is 5.

-h

Help. Print a command summary.

-s seconds

Call sync() at this interval. Default is 30.

-S

Always use sync() instead of flush.

-0 percent

Flush buffers when the specified percent of the buffer cache is dirty.

-1 blocks

The maximum number of dirty blocks to write out per wake cycle.

-2 buffers

The number of clean buffers to try to obtain each time the free buffers are refilled.

-3 blocks

Flush buffers if dirty blocks exceed blocks when trying to refill the buffers.

-4 percent

Percent of buffer cache to scan when looking for free clusters.

-5 seconds

Time for a data buffer to age before being flushed.

-6 seconds

Time for a nondata buffer to age before being flushed.

-7 constant

The time constant to use for load average.

-8 ratio

How low the load average can be before trimming back the number of buffers.