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https://github.com/kevinveenbirkenbach/create-linux-swapfile.git
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kevinveenbirkenbachandClaude Opus 5.5
91e1eff8a6
On a btrfs root the swapfile was written with dd from /dev/zero, so a swapfile the size of the RAM cost tens of GiB of writes and stalled every other writer on the filesystem. A caller that bounds the run, such as an async Ansible task, killed dd halfway, and the next run found the wrong size and started over. btrfs accepts a preallocated NOCOW swapfile and the swap directory already carries +C, so every filesystem now allocates with fallocate. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
104 lines
3.8 KiB
Bash
104 lines
3.8 KiB
Bash
#!/bin/sh
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# An unprivileged container cannot activate swap, so the run is expected to fail
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# at mkswap or swapon - which of the two depends on the host's /proc/swaps.
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# Everything before it - findmnt, fallocate, chmod - runs for real.
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set -eu
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fail() {
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echo "FAIL: $1" >&2
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exit 1
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}
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SWAPFORGE="$(command -v swap-forge)" || fail "swap-forge is not on PATH after install"
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echo "ok: swap-forge installed at ${SWAPFORGE}"
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command -v swafo >/dev/null || fail "the swafo alias is not on PATH after install"
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echo "ok: swafo alias installed"
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case "${SWAPFORGE}" in
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/usr/local/bin/*) ;;
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*) fail "swap-forge resolved to ${SWAPFORGE}, outside the install prefix" ;;
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esac
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echo "ok: resolved from the installed package, not the source tree"
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for binary in findmnt swapoff fallocate chmod mkswap swapon chattr btrfs; do
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command -v "${binary}" >/dev/null || fail "${binary} is missing from the image"
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done
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echo "ok: every declared binary is present"
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swap-forge --help | grep -q "Swapfile size" || fail "--help does not describe the tool"
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echo "ok: --help"
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set +e
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swap-forge >/dev/null 2>&1
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status=$?
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set -e
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[ "${status}" -eq 2 ] || fail "a missing size exited ${status}, expected 2"
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echo "ok: a missing size exits 2"
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set +e
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output="$(swap-forge 64T 2>&1)"
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status=$?
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set -e
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[ "${status}" -eq 1 ] || fail "an invalid size exited ${status}, expected 1"
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echo "${output}" | grep -q "Invalid size format" || fail "invalid size message wrong"
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if echo "${output}" | grep -q "Traceback"; then
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fail "an invalid size produced a traceback"
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fi
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echo "ok: an invalid size exits 1 without a traceback"
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printf 'UUID=deadbeef / ext4 defaults 0 1\n' >/etc/fstab
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cp /etc/fstab /tmp/fstab.before
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set +e
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output="$(swap-forge 8M 2>&1)"
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status=$?
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set -e
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[ "${status}" -eq 1 ] || fail "the blocked activation exited ${status}, expected 1"
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echo "${output}" | grep -q "Creating 8 MiB swapfile" || fail "the creation banner is missing"
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echo "${output}" | grep -qE "'(mkswap|swapon)' failed with exit code" || fail "the blocked activation was not reported cleanly"
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if echo "${output}" | grep -q "Traceback"; then
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fail "the blocked activation produced a traceback"
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fi
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echo "ok: real fallocate and chmod ran; the blocked activation exits 1 cleanly"
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[ -f /swapfile ] || fail "/swapfile was not created"
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size="$(stat -c %s /swapfile)"
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[ "${size}" -eq 8388608 ] || fail "/swapfile is ${size} bytes, expected 8388608"
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echo "ok: /swapfile exists with exactly the requested size"
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cmp -s /etc/fstab /tmp/fstab.before || fail "/etc/fstab changed although activation failed"
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echo "ok: /etc/fstab is untouched when activation fails"
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set +e
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output="$(swap-forge 8M 2>&1)"
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status=$?
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set -e
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[ "${status}" -eq 0 ] || fail "the idempotent rerun exited ${status}, expected 0"
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echo "${output}" | grep -q "already exists with correct size (8 MiB). Skipping." \
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|| fail "an existing swapfile of the right size was not detected"
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echo "ok: a rerun with the same size is a no-op - the idempotency the role relies on"
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set +e
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output="$(swap-forge 12M 2>&1)"
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status=$?
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set -e
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echo "${output}" | grep -q "has size 8 MiB, expected 12 MiB. Recreating..." \
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|| fail "a size change did not trigger a recreation"
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size="$(stat -c %s /swapfile)"
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[ "${size}" -eq 12582912 ] || fail "/swapfile is ${size} bytes after resize, expected 12582912"
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echo "ok: a different size really removes and recreates the swapfile"
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cmp -s /etc/fstab /tmp/fstab.before || fail "/etc/fstab changed during the resize cycle"
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echo "ok: /etc/fstab survived the resize cycle byte for byte"
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set +e
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output="$(env PATH=/nonexistent-bin "${SWAPFORGE}" 8M 2>&1)"
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status=$?
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set -e
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[ "${status}" -eq 127 ] || fail "missing findmnt exited ${status}, expected 127"
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echo "${output}" | grep -q "required command 'findmnt' is not installed" || fail "missing findmnt message wrong"
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echo "ok: missing findmnt exits 127 with a clean message"
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echo "ALL E2E CHECKS PASSED"
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