Alternate method of running swapon?

[Greg KH]

On Wed, Jan 08, 2020 at 01:09:23PM -0500, Jeffrey Walton wrote:
> Hi Everyone,
> 
> I work with an open source project. We have a VM but it is low-end.
> The machine suffers OOM kills. We don't have access to /etc/fstab.
> Everything is an upsell with the VPS provider.
> 
> I'm trying to setup a swapfile during startup using Systemd but:
> 
>     # swapon /swapfile
>     swapon: /swapfile: swapon failed: Operation not permitted
> 
> This may be useful:
> 
> # command -v swapon
> /sbin/swapon
> # file /sbin/swapo
> swapoff  swapon
> # file /sbin/swapon
> /sbin/swapon: ELF 64-bit LSB executable, x86-64, version 1 (SYSV),
> dynamically linked (uses shared libs), for GNU/Linux 2.6.32,
> BuildID[sha1]=a4891bc4dcfc533c61d76aa3e69870ab35d90c89, stripped
> 
> My question is, is there a way to sidestep the restriction? Is it
> possible to ask the kernel to use the swapfile without using the
> command?

Odds are the VPS provider is blocking it in the kernel they provide to
you.  You can always just try to write your own program that does the
same syscalls that 'swapon' does, but I doubt that works.

Perhaps spring for a bigger vm?

greg k-h