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<p>What is the usecase for this? sysexts are extensions to /usr (and
/opt). Services don't write to /usr usually (extensions are
usually read only too). Anything being read is opened as a fd
which survives the unmount-mount operation. I can't think of any
reason a service would want to "lock" /usr mountpoint.</p>
<p>Further if your service need to use binaries from patch extension
then you want to reload it somehow anyway.<br>
</p>
<p>Can you explain a bit more?</p>
<p>serene<br>
</p>
<div class="moz-cite-prefix">On 10/28/24 21:30, Umut Tezduyar
Lindskog wrote:<br>
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cite="mid:DU0PR02MB90257CB81505B85315A8E4C791282@DU0PR02MB9025.eurprd02.prod.outlook.com">
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<p class="MsoNormal">Hello systemd,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">We are looking into systemd system
extensions for quick patching our immutable images while we
are updating and rolling out the patched immutable image. <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">One thing that is stated in the
documentation is that before attaching a new extension, all
previous extensions are deattached and everything are attached
again. We understand that this sequence is needed for
overlayfs stacking in case something has changed in the stack
with the new extension. <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">For our use case, we would like to be able
to push multiple patch extensions (ex: couple of days apart)
while keeping the service downtime to<span lang="EN-US"> a</span> minimum.
Technically we believe that if the extensions are not
overlapping there is no need to detach already attached
extensions. There is no built in option in systemd extensions
to keep the existing extensions right? Due to how overlayfs
works, they temporarly need to be removed and the<span
lang="EN-US">n</span>brought up again, during a refresh
operation. <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">While on the topic, we have investigated
other file systems. One we put our attention to is mergerfs,
which is a fuse file system to allows "mount points" to be
dynamically added/removed without doing a mount/unmount. Is
there support in systemd extensions to let system extension
work with other file systems than overlayfs?<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US">Thanks</span><o:p></o:p></p>
<p class="MsoNormal"><span lang="EN-US">Umut</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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