| 1 | .\" @(#)update.8 4.1 (Berkeley) %G% |
| 2 | .\" |
| 3 | .TH UPDATE 8 "4/1/81" |
| 4 | .AT 3 |
| 5 | .SH NAME |
| 6 | update \- periodically update the super block |
| 7 | .SH SYNOPSIS |
| 8 | .B /etc/update |
| 9 | .SH DESCRIPTION |
| 10 | .I Update |
| 11 | is a program that executes |
| 12 | the |
| 13 | .IR sync (2) |
| 14 | primitive every 30 seconds. |
| 15 | This insures that the file system |
| 16 | is fairly up to date in case of a crash. |
| 17 | This command should not be executed directly, |
| 18 | but should be executed out of the |
| 19 | initialization shell command file. |
| 20 | .SH "SEE ALSO" |
| 21 | sync(2), sync(1), init(8) |
| 22 | .SH BUGS |
| 23 | With |
| 24 | .I update |
| 25 | running, |
| 26 | if the CPU is |
| 27 | halted just as |
| 28 | the |
| 29 | .I sync |
| 30 | is executed, |
| 31 | a file system can be damaged. |
| 32 | This is partially due to DEC hardware that |
| 33 | writes zeros when NPR requests fail. |
| 34 | A fix would be to have |
| 35 | .IR sync (1) |
| 36 | temporarily increment the system time by at |
| 37 | least 30 seconds to trigger the execution of |
| 38 | .I update. |
| 39 | This would give 30 seconds grace to halt the CPU. |