Which script allocates /var/swap.img on second boot?

[Tarmo Kuuse]

Hi!

I flashed an rcn-ee image into eMMC (bone-debian-8.7-seeed-iot-armhf-2017-01-15-4gb.img.xz). On first boot there's no swap anywhere.

On second boot something allocates /var/swap.img and installs it as swap in fstab. This seems to happen right after the root filesystem is remounted. dmesg says:

[   31.270174] EXT4-fs (mmcblk1p1): re-mounted. Opts: errors=remount-ro

[   31.717598] Adding 262140k swap on /var/swap.img.  Priority:-1 extents:10 across:745468k SSFS

I'd really like to snip that. Any hints where to look?

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Kind regards,

Tarmo Kuuse

[William Hermans]

So . . .

root@beaglebone:~# systemctl status generic-board-startup.service
● generic-board-startup.service - Generic Board Startup
   Loaded: loaded (/lib/systemd/system/generic-board-startup.service; disabled; vendor preset: enabled)
   Active: inactive (dead)

This service is responsible for starting up the scripts in /opt/scripts/boot. Personally, I disable it because it loads things I don't want running. I do believe that one of the scripts in /opt/scripts/boot "mentions" swap. So you can start by looking through those.

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[William Hermans]

By the way, if you use USB networking. Don't disable this service, and don't move, or delete any of the scripts in /opt/scripts/boot

[Robert Nelson]

Me too...

It's definitely not something i added to the default images by default..

Are you sure you didn't enable it yourself?

(doesn't even run swap on my debian x86 development machine)

Regards,

--
Robert Nelson
https://rcn-ee.com/

[William Hermans]

On Thu, Jan 19, 2017 at 7:44 AM, Robert Nelson <robert...@gmail.com> wrote:
>
>
> Me too...
>
> It's definitely not something i added to the default images by default..
>
> Are you sure you didn't enable it yourself?
>
> (doesn't even run swap on my debian x86 development machine)
>
> Regards,
>
> --
> Robert Nelson
> https://rcn-ee.com/

Is this possibly related to zram ? I noticed that zram is in the kernel I use. While not strictly speaking *only* for swap disks in memory. Many seem to relate zram to doubling their memory by running a compressed swap disk in RAM.

[Robert Nelson]

flashed bone-debian-8.7-seeed-iot-armhf-2017-01-15-4gb.img.xz

after a few reboot's still no random swap file...

root@beaglebone:~# journalctl | grep swap
May 21 22:31:30 beaglebone kernel: zswap: loaded using pool lzo/zbud

[Robert Nelson]

other then enabling that module, zram is currently un-used..

https://wiki.gentoo.org/wiki/Zram

[Tarmo Kuuse]

It turns out that systemd is configured to maintain a swap file. This is what I did to make it stop:

List systemd-s swap units:
$ sudo systemctl --type swap

Disable a swap unit named "var-swap.img.swap":

$ sudo systemctl mask var-swap.img.swap

--
Kind regards,

Tarmo Kuuse

[Tarmo Kuuse]

Aaaaand of course swap is set up by one of our ansible configuration scripts which I didn't grep out initially. 

Sorry for the confusion. Robert's images don't install swap.

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Kind regards,

Tarmo Kuuse