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| author |   Adam Borowski <kilobyte@angband.pl> | 2019-09-03 18:08:40 +0200 |
|---|---|---|
| committer |   Jonathan Corbet <corbet@lwn.net> | 2019-09-06 08:42:52 -0600 |
| commit | 209c3aa7f0df27feb824c179a763ace3e667c8ba (patch) | |
| tree | 3298487886f6283b1f9691e43d2cea6c1b06f1f9 /Documentation/admin-guide/sysrq.rst | |
| parent | mailmap: Update email address for Quentin Perret (diff) | |
| download | wireguard-linux-209c3aa7f0df27feb824c179a763ace3e667c8ba.tar.xz wireguard-linux-209c3aa7f0df27feb824c179a763ace3e667c8ba.zip | |
Documentation: sysrq: don't recommend 'S' 'U' before 'B'
This advice is obsolete and slightly harmful for filesystems from this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@angband.pl>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/admin-guide/sysrq.rst')
| -rw-r--r-- | Documentation/admin-guide/sysrq.rst | 20 |
1 files 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 |