forked from wrenn/wrenn
Rafeed M. Bhuiyan
05ddf62399
Co-authored-by: Tasnim Kabir Sadik <tksadik@omukk.dev> Reviewed-on: wrenn/wrenn#50
66 lines
2.9 KiB
Bash
66 lines
2.9 KiB
Bash
#!/bin/sh
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# wrenn-init: minimal PID 1 init for Cloud Hypervisor microVMs.
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# Mounts virtual filesystems, starts chronyd for time sync, then execs tini + envd.
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set -e
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# Mount essential virtual filesystems if not already mounted.
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mount -t proc proc /proc 2>/dev/null || true
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mount -t sysfs sysfs /sys 2>/dev/null || true
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mount -t devtmpfs devtmpfs /dev 2>/dev/null || true
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mkdir -p /dev/pts /dev/shm
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mount -t devpts devpts /dev/pts 2>/dev/null || true
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mount -t tmpfs tmpfs /dev/shm 2>/dev/null || true
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mount -t tmpfs tmpfs /tmp 2>/dev/null || true
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mount -t tmpfs tmpfs /run 2>/dev/null || true
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mkdir -p /sys/fs/cgroup
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mount -t cgroup2 cgroup2 /sys/fs/cgroup 2>/dev/null || true
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echo "+cpu +memory +io" > /sys/fs/cgroup/cgroup.subtree_control 2>/dev/null || true
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# Disable write_zeroes and discard on rootfs — dm-snapshot doesn't support
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# these ops, but CH advertises them anyway. Suppress at block queue level.
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# sysfs attributes are read-only on some kernels, so failures are expected.
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{ echo 0 > /sys/block/vda/queue/write_zeroes_max_bytes; } 2>/dev/null || true
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{ echo 0 > /sys/block/vda/queue/discard_max_bytes; } 2>/dev/null || true
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# Set hostname and make it resolvable (sudo requires this). Use the kernel knob
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# directly so we don't depend on the `hostname` binary, which is absent from
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# minimal Arch/Fedora images. Guard so a failure never aborts init under set -e.
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echo capsule > /proc/sys/kernel/hostname 2>/dev/null || hostname capsule 2>/dev/null || true
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echo "127.0.0.1 capsule" >> /etc/hosts 2>/dev/null || true
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# Configure networking if the kernel ip= boot arg did not already set it up.
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if ! ip addr show eth0 2>/dev/null | grep -q "169.254.0.21"; then
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ip link set lo up 2>/dev/null || true
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ip link set eth0 up 2>/dev/null || true
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ip addr add 169.254.0.21/30 dev eth0 2>/dev/null || true
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ip route add default via 169.254.0.22 2>/dev/null || true
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fi
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# Configure DNS resolver. Drop any existing symlink first — on some distros
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# (e.g. Fedora) /etc/resolv.conf is a dangling symlink into systemd-resolved,
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# and writing through it would fail and abort init under set -e.
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rm -f /etc/resolv.conf 2>/dev/null || true
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{
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echo "nameserver 8.8.8.8"
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echo "nameserver 8.8.4.4"
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} > /etc/resolv.conf 2>/dev/null || true
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# Set a standard PATH so envd and all child processes can find common binaries.
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export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
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# Write chrony config to sync time from the KVM PTP hardware clock.
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# /dev/ptp0 is a paravirtual clock exposed by KVM — no network required.
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mkdir -p /etc/chrony /run/chrony
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cat > /etc/chrony/chrony.conf <<EOF
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refclock PHC /dev/ptp0 poll 2 dpoll 2
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driftfile /run/chrony/chrony.drift
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makestep 1.0 -1
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EOF
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# Start chronyd in the background before handing off to tini.
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chronyd -f /etc/chrony/chrony.conf 2>/dev/null || true
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# Exec tini as PID 1 — it reaps zombie processes and forwards signals to envd.
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exec /sbin/tini -- /usr/local/bin/envd
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