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Hello systemd developers,</div>
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I'm working on minimizing user space boot time with systemd on an embedded board and would appreciate any advice or insights from the community.</div>
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<span style="font-weight: 550;">Setup details:</span></div>
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<div style="margin: 0px;" role="presentation"><span style="font-weight: 550;">Hardware:</span> sam9x75-curiosity-sd (ARMv5), booting from SD card</div>
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<div style="margin: 0px;" role="presentation"><span style="font-weight: 550;">Distro:</span> Yocto/Poky, custom minimal image</div>
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<div style="margin: 0px;" role="presentation"><span style="font-weight: 550;">Storage:</span> root on
<span style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace; font-weight: 550;">
<code style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace;">/dev/root</code></span> (SD),
<span style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace; font-weight: 550;">
<code style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace;">/boot</code></span> on
<span style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace; font-weight: 550;">
<code style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace;">/dev/mmcblk0p1</code></span></div>
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<div style="margin: 0px;" role="presentation"><span style="font-weight: 550;">Systemd:</span> extensive minimization</div>
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<div style="margin: 0px;" role="presentation">All optional features/daemons are disabled (via Meson and PACKAGECONFIG), no LVM, RAID, or swap</div>
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<div style="margin: 0px;" role="presentation">Only essential units (<span style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace; font-weight: 550;"><code style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace;">fastboot.target</code></span>,
custom <span style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace; font-weight: 550;">
<code style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace;">hmi.service</code></span>, minimal getty and dbus)</div>
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<div style="margin: 0px;" role="presentation">No unnecessary entries in <span style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace; font-weight: 550;">
<code style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace;">/etc/fstab</code></span>; root and
<span style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace; font-weight: 550;">
<code style="font-family: berkeleyMono, "berkeleyMono Fallback", ui-monospace, SFMono-Regular, monospace;">/boot</code></span> only</div>
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<div style="margin: 0px;" role="presentation">Kernel configured for minimal drivers and fast boot</div>
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<div style="margin: 0px;" role="presentation"><span style="font-weight: 550;">No unnecessary settle or legacy storage services remain enabled</span></div>
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<span style="font-weight: 550;">Boot logs:</span></div>
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<pre style="margin: 0px; border-radius: 0.25rem; width: 740px;" class="elementToProof"><div style="margin-top: 16px; margin-bottom: 16px; border-radius: 0.25rem;" class="elementToProof"><div style="padding-right: 32px;" class="elementToProof"><div style="text-align: left; text-indent: 0px; line-height: 1.42857; border-radius: 3px; font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);" class="elementToProof"><span style="font-weight: 100;"><code># systemd-analyze time
Startup finished in 771ms (kernel) + 2.715s (userspace) = 3.486s
fastboot.target reached after 2.231s in userspace.
# systemd-analyze blame
422ms hmi.service
# systemd-analyze critical-chain fastboot.target
fastboot.target @2.231s
# systemctl get-default
fastboot.target
# ls /lib/systemd/system/fastboot.target.wants/
console-getty.service dbus.socket hmi.service
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I've reviewed <span style="color: oklch(0.3039 0.04 213.68);"><u><a style="color: oklch(0.3039 0.04 213.68);" rel="nofollow noopener" class="break-word hover:text-super hover:decoration-super underline decoration-from-font underline-offset-1 transition-all duration-300 OWAAutoLink" id="OWAd5d6d4ac-1a11-02b4-817c-0a3e9a0ce30b" target="_blank" href="https://systemd.io/OPTIMIZATIONS/">systemd.io/OPTIMIZATIONS</a></u></span> and
applied all recommendations relevant to my scenario (disabling settle services, removing legacy storage stacks, fixing locale, etc.).</div>
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<span style="font-weight: 550;">Question:</span><br>
Given the above, is it realistic to further reduce systemd userspace boot time below 2 seconds on such an SD-boot, minimal embedded board? Are there advanced tunables, overlooked dependencies, or hardware-specific factors I should consider to claw back a few
hundred milliseconds? Any experience or pointers—especially from similar setups—are very welcome.</div>
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Thanks in advance!</div>
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With Best Regards,</div>
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Dharma B</div>
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