This advice is obsolete and slightly harmful for filesystems from this millenium: any modern filesystem can handle unexpected crashes without requiring fsck -- and on the other hand, trying to write to the disk when the kernel is in a bad state risks introducing corruption. For ext2, any unsafe shutdown meant widespread breakage, but it's no longer a reasonable filesystem for any non-special use. Signed-off-by: Adam Borowski <kilobyte@xxxxxxxxxx> --- Documentation/admin-guide/sysrq.rst | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst index 7b9035c01a2e..72b2cfb066f4 100644 --- a/Documentation/admin-guide/sysrq.rst +++ b/Documentation/admin-guide/sysrq.rst @@ -171,22 +171,20 @@ It seems others find it useful as (System Attention Key) which is useful when you want to exit a program that will not let you switch consoles. (For example, X or a svgalib program.) -``reboot(b)`` is good when you're unable to shut down. But you should also -``sync(s)`` and ``umount(u)`` first. +``reboot(b)`` is good when you're unable to shut down, it is an equivalent +of pressing the "reset" button. ``crash(c)`` can be used to manually trigger a crashdump when the system is hung. Note that this just triggers a crash if there is no dump mechanism available. -``sync(s)`` is great when your system is locked up, it allows you to sync your -disks and will certainly lessen the chance of data loss and fscking. Note -that the sync hasn't taken place until you see the "OK" and "Done" appear -on the screen. (If the kernel is really in strife, you may not ever get the -OK or Done message...) +``sync(s)`` is handy before yanking removable medium or after using a rescue +shell that provides no graceful shutdown -- it will ensure your data is +safely written to the disk. Note that the sync hasn't taken place until you see +the "OK" and "Done" appear on the screen. -``umount(u)`` is basically useful in the same ways as ``sync(s)``. I generally -``sync(s)``, ``umount(u)``, then ``reboot(b)`` when my system locks. It's saved -me many a fsck. Again, the unmount (remount read-only) hasn't taken place until -you see the "OK" and "Done" message appear on the screen. +``umount(u)`` can be used to mark filesystems as properly unmounted. From the +running system's point of view, they will be remounted read-only. The remount +isn't complete until you see the "OK" and "Done" message appear on the screen. The loglevels ``0``-``9`` are useful when your console is being flooded with kernel messages you do not want to see. Selecting ``0`` will prevent all but -- 2.23.0
