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Diffstat (limited to 'Documentation/power/swsusp.txt')
| -rw-r--r-- | Documentation/power/swsusp.txt | 51 |
1 files changed, 44 insertions, 7 deletions
diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt index b28b7f04abb8..d7814a113ee1 100644 --- a/Documentation/power/swsusp.txt +++ b/Documentation/power/swsusp.txt @@ -17,6 +17,11 @@ Some warnings, first. * but it will probably only crash. * * (*) suspend/resume support is needed to make it safe. + * + * If you have any filesystems on USB devices mounted before suspend, + * they won't be accessible after resume and you may lose data, as though + * you have unplugged the USB devices with mounted filesystems on them + * (see the FAQ below for details). You need to append resume=/dev/your_swap_partition to kernel command line. Then you suspend by @@ -27,19 +32,18 @@ echo shutdown > /sys/power/disk; echo disk > /sys/power/state echo platform > /sys/power/disk; echo disk > /sys/power/state +. If you have SATA disks, you'll need recent kernels with SATA suspend +support. For suspend and resume to work, make sure your disk drivers +are built into kernel -- not modules. [There's way to make +suspend/resume with modular disk drivers, see FAQ, but you probably +should not do that.] + If you want to limit the suspend image size to N bytes, do echo N > /sys/power/image_size before suspend (it is limited to 500 MB by default). -Encrypted suspend image: ------------------------- -If you want to store your suspend image encrypted with a temporary -key to prevent data gathering after resume you must compile -crypto and the aes algorithm into the kernel - modules won't work -as they cannot be loaded at resume time. - Article about goals and implementation of Software Suspend for Linux ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -333,4 +337,37 @@ init=/bin/bash, then swapon and starting suspend sequence manually usually does the trick. Then it is good idea to try with latest vanilla kernel. +Q: How can distributions ship a swsusp-supporting kernel with modular +disk drivers (especially SATA)? + +A: Well, it can be done, load the drivers, then do echo into +/sys/power/disk/resume file from initrd. Be sure not to mount +anything, not even read-only mount, or you are going to lose your +data. + +Q: How do I make suspend more verbose? + +A: If you want to see any non-error kernel messages on the virtual +terminal the kernel switches to during suspend, you have to set the +kernel console loglevel to at least 5, for example by doing + + echo 5 > /proc/sys/kernel/printk + +Q: Is this true that if I have a mounted filesystem on a USB device and +I suspend to disk, I can lose data unless the filesystem has been mounted +with "sync"? + +A: That's right. It depends on your hardware, and it could be true even for +suspend-to-RAM. In fact, even with "-o sync" you can lose data if your +programs have information in buffers they haven't written out to disk. + +If you're lucky, your hardware will support low-power modes for USB +controllers while the system is asleep. Lots of hardware doesn't, +however. Shutting off the power to a USB controller is equivalent to +unplugging all the attached devices. + +Remember that it's always a bad idea to unplug a disk drive containing a +mounted filesystem. With USB that's true even when your system is asleep! +The safest thing is to unmount all USB-based filesystems before suspending +and remount them after resuming. |