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Re: "enabling zram.service on LiveOS boots"



On Wed, Jun 19, 2019 at 10:33 AM Brian C. Lane <bcl redhat com> wrote:
>
> On Wed, Jun 19, 2019 at 01:24:27PM +0200, jkonecny redhat com wrote:
> > Hi Chris,
> >
> > There has to be change in the live media creation. Anaconda don't have
> > power on what is booted on Live DVD.
> >
> > I think the Fedora kickstart used to create the DVD Live image is the
> > change target here. That kickstart should enable the service so it will
> > be auto-started during the Live DVD boot. However, if we do that then
> > the service will be also enabled on the installed system which is
> > probably not what we wanted to do...
>
> Correct. The place to enable it would be in the livesys script that the
> %post section writes. But I'm not sure if that's too late in the boot
> process for it to be useful. As long as it is just started, not enabled,
> from the script it should only run when booting the live iso and not the
> installed system.

Or can Anaconda just 'systemctl start zram.service' when it's
launched, whether on Live or netinstall?

The problems I'm seeing only in low memory situations, doesn't arise
until Anaconda launches. So it's fine if 'systemctl start
zram.service' happens late.

Looks like the change would go in
https://pagure.io/fedora-kickstarts/blob/master/f/fedora-live-base.ks

It contains this section:
   110    # enable swaps unless requested otherwise
   111    swaps=\`blkid -t TYPE=swap -o device\`
   112    if ! strstr "\`cat /proc/cmdline\`" noswap && [ -n "\$swaps" ] ; then
   113      for s in \$swaps ; do
   114        action "Enabling swap partition \$s" swapon \$s
   115      done
   116    fi
   117    if ! strstr "\`cat /proc/cmdline\`" noswap && [ -f
/run/initramfs/live/\${livedir}/swap.img ] ; then
   118      action "Enabling swap file" swapon
/run/initramfs/live/\${livedir}/swap.img
   119    fi

Umm, anyone got any opinions on removing that whole thing?

a) I don't really see the point of using some legacy swap partition
that the installer has some chance of needing to turn off in order to
modify partitioning or what have you?

b) Silently activating a persistent swap is a security leak for LiveOS
users, unless testing for encryption or setting up /dev/urandom key
based encryption for it.

Also, there is a package, zram-0.3-1.fc30.noarch, which is more
recently developed and intended to be generic use. Any chance of
deprecating the anaconda zram stuff and depending on this zram package
instead?
https://src.fedoraproject.org/rpms/zram/tree/master

Last, it looks like the systemd folks want to turn all of this into
native systemd units, and get rid of the livesys script entirely.

-- 
Chris Murphy


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