Move swap to USB - Printable Version

Move swap to USB - Printable Version

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Move swap to USB - rlogiacco - 4th Aug, 2014 04:31 AM

After moving my root filesystem over an external USB drive I was performing some configuration task and just by accident I saw this line logged by dmesg

Code:

[77395.117621] Adding 250876k swap on /dev/mmcblk0p3.  Priority:0 extents:1 across:250876k SSFS

I then checked if that message had any correspondence and, to my surprise:

Code:

$ sudo swapon -s

Filename                                Type            Size    Used    Priority

/dev/mmcblk0p3                          partition       250876  144     0

Now, my cmdline.txt has the following directives related to swap:

Code:

zswap.enabled=1 zswap.compressor=lz4 noswap partswap

I believe the latter partswap is the source of my problems as I don/t have a swap partition on my USB disk, I thought a swap file would do.

I'm going to eliminate the swappart directive, but in case it is not going to solve... where do I specify the zswap configuration? I have nothing relevant in my /etc/fstab....

As I supposed, removing partswap didn't help and removing noswap made the swap partition on sd card get inited at boot.

Humm, I believe I've got some progress on this... Inside /etc/init/zram-swap.conf I've found

Code:

SWAPPART="$(blkid -t TYPE=swap | grep -v 'zram\|loop'| awk -F':' '{print $1}')"

        if [ -z "$SWAPPART" ]; then

            swapfile

        else

            swappart

        fi

I belive I will have to modify this script or remove the swap partition on the SD card to avoid to have it loaded....

On a second thought though having the swap file/partition ona different device than root fs should not be that bad: my only concern is about life expectancy of the SD card... but if I understand zswap it should activate the swap partition only when really needed... Am I wrong on this?

RE: Move swap to USB - CurlyMo - 4th Aug, 2014 04:59 AM

Quote:I understand zswap it should activate the swap partition only when really needed...

Yes, you can check this by doing:

Code:

free -m

RE: Move swap to USB - mk01 - 6th Aug, 2014 09:15 PM

partswap parameter should during enabled initramfs do this:

1) check if rootfstype=btrfs
2) check if root= is last partition on the block device
3) shrink root
4) create new partition
5) make swap on it

exactly this way is created swap upon first boot.