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09-26-2002 07:07 AM
09-26-2002 07:07 AM
Sync command details
Create core file?
Crash system?
etc?
Thanks!
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09-26-2002 07:12 AM
09-26-2002 07:12 AM
Re: Sync command details
The 'sync' command should do none of the above. Here is a snippet from the man page for 'sync':
sync executes the sync() system call (see sync(2)). If the system is
to be stopped, the sync command must be called to ensure file system
integrity.
sync flushes all previously unwritten system buffers including
modified super blocks, modified inodes, and delayed block I/O out to
disk. This ensures that all file modifications are properly saved
before performing a critical operation such as a system shutdown. For
additional protection from power failures or possible system crashes,
use syncer to execute sync automatically at periodic intervals (see
syncer(1M)).
I'm curious. Why do you ask?
JP
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09-26-2002 07:12 AM
09-26-2002 07:12 AM
Re: Sync command details
# man 1m sync
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09-26-2002 07:15 AM
09-26-2002 07:15 AM
Re: Sync command details
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09-26-2002 07:25 AM
09-26-2002 07:25 AM
Re: Sync command details
JP
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09-26-2002 07:33 AM
09-26-2002 07:33 AM
Re: Sync command details
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09-26-2002 07:39 AM
09-26-2002 07:39 AM
Re: Sync command details
Sync command is just used to ensure that all files which have not been written to the system are written immediately.
So all processes or changes which are held for writing to the system get committed and the system is updated completely for any changes withheld.
It has got nothing to do with core file or crash system.
Regards,
Anil
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09-26-2002 07:52 AM
09-26-2002 07:52 AM
Re: Sync command details
The sync command will sync the memory buffers with the disk. So if there was an update in the memory but not yet synced to disk, it will be done with the sync command. Do "man sync" for more details.
Hope this helps.
Regds
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09-27-2002 04:57 AM
09-27-2002 04:57 AM
Re: Sync command details
Are you trying to force a system panic on demand and verify that a proper crash dump is created? If so, forget about sync and:
On series 700 systems, look for a small button marked 'TOC' on the system chassis and push it.
On series 800 systems, be sure the key switch (or, on some systems, a switch on the back of the machine) is in the 'service' position then type ^B on the system console, followed by 'tc' and a newline. Typically you then have to type a
'y' to confirm that you want to take the system down forcefully. The process for this can vary a bit from machine to machine.
In both cases you are effectively generating a non-maskable interrupt (a Transfer of Control -I'll bet you can now guess what 'tc' stands for) that causes the system to jump to a routine that forces a crash dump to be taken. The system will come down very ungracefully, with the chance of some (usually very minor and easily recovered from) disk corruption, since the system has not had a chance to cleanly stop processing.
There is one tie from this back to your original 'sync' comment:
Running 'sync' just before doing the above can reduce the risk of disk corruption. Normally there is a background process called syncer that will essentially run 'sync' every 30 seconds or so. During normal operation, you don't have to worry at all about that. If you know the system is about to die, forcing a sync to happen at that time may be helpful in reducing the risk of damage.
Was that what you were really asking? If not, let's try again to understand your question.