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https://github.com/kuhyx/testsAndMisc.git
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Krzysztof kuhy Rudnicki
b57d5f9064
The periodic setup wrote /usr/local/bin scripts with sed > target, truncating the file in place. bash reads scripts lazily, so the running hosts-file-monitor could execute a half-new file. New lib/atomic_install.sh renders into a temp file beside the target, syntax-checks it, sets mode/owner and renames it over the target (new inode). A bad template fails closed and leaves the live file untouched. Applied to the maintenance script, hosts monitor, browser wrapper and auto-update script; the hosts monitor service is restarted if running. Test: test_services_atomic_install.sh (inode changes, old inode keeps old bytes, syntax error and missing template leave target untouched). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01WzxdWYWDKuhbBAoNETfoB9
51 lines
1.8 KiB
Bash
Executable File
51 lines
1.8 KiB
Bash
Executable File
#!/bin/bash
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# Atomic install of live /usr/local/bin scripts for the periodic system setup.
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#
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# Sourced by setup_periodic_system.sh and periodic_browser.sh.
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#
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# Why not `sed ... > /usr/local/bin/x.sh`: that truncates the file in place.
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# bash reads a script lazily, so a service already running it (the hosts
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# monitor loops forever) can execute a half-new file. Rendering beside the
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# target and renaming over it gives the target a NEW inode; a running instance
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# keeps reading the old one until it exits or is restarted.
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# Fail-closed: a template that is missing or fails `bash -n` leaves the live
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# file untouched and returns non-zero.
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# install_rendered_script <template> <dest> [sed args...]
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# Renders <template> through sed with the given args into a temp file in
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# dirname(<dest>) (same filesystem, so mv is a rename), syntax-checks it, sets
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# mode 0755 and root ownership when run as root, then renames it over <dest>.
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install_rendered_script() {
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local template="$1" dest="$2"
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shift 2
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local tmp
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[[ -f $template ]] || {
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echo "Error: template not found: $template" >&2
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return 1
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}
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tmp="$(mktemp "${dest}.XXXXXX")" || return 1
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# `-e ''` keeps sed valid when the caller passes no expressions.
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if sed -e '' "$@" "$template" >"$tmp" &&
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bash -n "$tmp" &&
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chmod 0755 "$tmp" &&
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{ [[ $EUID -ne 0 ]] || chown root:root "$tmp"; } &&
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mv -f "$tmp" "$dest"; then
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return 0
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fi
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rm -f "$tmp"
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echo "Error: not installing $dest (render or syntax check failed)" >&2
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return 1
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}
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# restart_if_active <unit>
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# Restarts a unit onto a freshly installed script, but only if it is running:
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# the installer must not start a service the user stopped on purpose.
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restart_if_active() {
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local unit="$1"
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if systemctl is-active "$unit" >/dev/null 2>&1; then
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systemctl restart "$unit"
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echo "✓ Restarted $unit onto the new script"
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fi
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return 0
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}
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