build: execute daemon-reload and restart postinst in deb

[aminvakil]

Follow up to #10844 and #8341 and #8330.

Testing
Before we can approve your change; please submit the following in a comment:

• [N/A] Example configuration file for the change
• [N/A] Debug log output from testing the change

• [N/A] Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• Run local packaging test showing all targets (including any new ones) build.
• Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [N/A] Documentation required for this feature

Backporting

• [N/A] Backport to latest stable release.

---

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• New Features

  • Added a Debian post-install step that reloads system services and attempts to restart the application after install/upgrade, improving out-of-the-box readiness.
  • Post-install actions run quietly with tolerant failure handling for smoother upgrades.

• Chores

  • Improved Debian package assembly to reliably include maintainer scripts (post-install and pre-remove).
  • Streamlined packaging flow to ensure scripts are generated before building the package, enhancing installation reliability.

[aminvakil]

Initial attempt on ./packaging/local-build-all.sh failed here which is irrelevant to this PR.

+ docker build --build-arg CMAKE_INSTALL_PREFIX=/opt/fluent-bit/ --build-arg FLB_NIGHTLY_BUILD= --build-arg FLB_JEMALLOC=On --build-arg FLB_TD=Off --build-arg FLB_UNICODE_ENCODER=On --build-arg BASE_BUILDER=amazonlinux-2.arm64v8-base --target builder -t flb-amazonlinux/2.arm64v8 -f /tmp/fluent-bit/packaging/distros/amazonlinux/Dockerfile /tmp/fluent-bit/packaging/..
[+] Building 1.4s (3/3) FINISHED                                                                                                                                                                                             docker:default
 => [internal] load build definition from Dockerfile                                                                                                                                                                                   0.0s
 => => transferring dockerfile: 5.90kB                                                                                                                                                                                                 0.0s
 => WARN: InvalidDefaultArgInFrom: Default value for ARG $BASE_BUILDER results in empty or invalid base image name (line 118)                                                                                                          0.0s
 => CANCELED [internal] load metadata for docker.io/multiarch/qemu-user-static:x86_64-aarch64                                                                                                                                          1.2s
 => ERROR [internal] load metadata for docker.io/arm64v8/amazonlinux:2                                                                                                                                                                 1.2s
------
 > [internal] load metadata for docker.io/arm64v8/amazonlinux:2:
------

 1 warning found (use docker --debug to expand):
 - InvalidDefaultArgInFrom: Default value for ARG $BASE_BUILDER results in empty or invalid base image name (line 118)
Dockerfile:37
--------------------
  35 |     
  36 |     # amazonlinux/2.arm64v8 base image
  37 | >>> FROM arm64v8/amazonlinux:2 AS amazonlinux-2.arm64v8-base
  38 |     
  39 |     COPY --from=multiarch-aarch64 /usr/bin/qemu-aarch64-static /usr/bin/qemu-aarch64-static
--------------------
ERROR: failed to build: failed to solve: arm64v8/amazonlinux:2: failed to resolve source metadata for docker.io/arm64v8/amazonlinux:2: no match for platform in manifest: not found
+ echo 'Error building main docker image flb-amazonlinux/2.arm64v8'
Error building main docker image flb-amazonlinux/2.arm64v8

[aminvakil]

I've commented anything other debian 11 and debian 12 and it's not working.

[aminvakil]

This has broken other stuff
postinst after last commit:

#!/bin/sh
set -e

if [ "$1" = "configure" ]; then
    systemctl daemon-reload >/dev/null || true
    systemctl try-restart fluent-bit.service >/dev/null || true
fi
exit 0

Currently it is:

#!/bin/sh

set -e

if [ "$1" = "configure" ]; then
        ldconfig
fi

Also conffiles is missing.

[aminvakil]

It's correct now.
postinst:

#!/bin/sh
set -e

if [ "$1" = "configure" ]; then
    systemctl daemon-reload >/dev/null || true
    systemctl try-restart fluent-bit.service >/dev/null || true
fi
exit 0

It restarts service when it's already started, it does not start the service if it has not been started already.
Also it always executes systemd daemon-reload which is fine IMO.

For testing with FLB_RUN_LDCONFIG on I'm going to change this line:

option(FLB_RUN_LDCONFIG "Enable execution of ldconfig after installation" No)

to

option(FLB_RUN_LDCONFIG "Enable execution of ldconfig after installation" Yes)

in CMakelists.txt, build package and test it.

[aminvakil]

With

option(FLB_RUN_LDCONFIG "Enable execution of ldconfig after installation" Yes)

in CMakelists.txt

$ cat ./prerm 

rm -f -- /etc/ld.so.conf.d/libfluent-bit.conf
ldconfig
$ cat ./postinst 
#!/bin/sh
set -e

mkdir -p /etc/ld.so.conf.d
echo "lib/fluent-bit" > /etc/ld.so.conf.d/libfluent-bit.conf
ldconfig
    
if [ "$1" = "configure" ]; then
    systemctl daemon-reload >/dev/null || true
    systemctl try-restart fluent-bit.service >/dev/null || true
fi

[aminvakil]

There is another issue in prerm, fluent-bit does not stop its service and daemon-reload before rm, but I guess that can be for another PR.

It's ready for review now.

[aminvakil]

I do not know the policies for this repository, but I had Gemini's help for creating this PR, but I've tested final deb file on a debian bullseye as stated in my comments.

[aminvakil]

Note to myself: Is this the correct approach or should I use deb-systemd-helper?

[aminvakil]

Failing tests are irrelevant to this PR:

 Package clang-12 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'clang-12' has no installation candidate

Package awscli is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'awscli' has no installation candidate

There is also windows fix which is failing.
Debian bookworm deb for example has been created.
https://github.com/fluent/fluent-bit/actions/runs/17836661477/artifacts/4055367546

[patrick-stephens]

Can you rebase? The awscli issue is related to the arm image but it's resolved in master

[aminvakil]

Can you rebase? The awscli issue is related to the arm image but it's resolved in master

Yep, I saw that and already rebased.

[aminvakil]

Failing tests are irrelevant to this PR.

[coderabbitai]

📝 Walkthrough

Walkthrough

Introduces a templated Debian post-install script and updates CMake packaging flow to generate it via configure_file. Accumulates package control extras using list(APPEND), ensuring generated postinst and existing prerm are included. Replaces inline file writes with a variable-based command list for postinst content.

Changes

Cohort / File(s)	Change Summary
CMake packaging configuration CMakeLists.txt	Added LDCONFIG_SCRIPT_CMDS accumulator; replaced inline file(WRITE ...) with configure_file(...) to produce ${PROJECT_BINARY_DIR}/scripts/postinst from cpack/debian/postinst.in; switched CPACK_DEBIAN_RUNTIME_PACKAGE_CONTROL_EXTRA to list(APPEND ...) and ensured inclusion of generated postinst and existing prerm.
Debian postinst script template cpack/debian/postinst.in	New template script: executes accumulated post-install commands; on configure/abort-* actions, if systemd exists, runs daemon-reload and attempts to restart FLB_OUT_NAME service with tolerant error handling.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant Dev as Developer
  participant CMake as CMake (configure)
  participant CFG as configure_file
  participant CPack as CPack (package)
  participant dpkg as dpkg (install)
  participant Post as postinst script
  participant systemd as systemd

  Dev->>CMake: Configure project
  CMake->>CFG: Generate scripts/postinst from cpack/debian/postinst.in
  Note right of CFG: Inject LDCONFIG_SCRIPT_CMDS into template
  CMake->>CPack: Set CPACK_DEBIAN_RUNTIME_PACKAGE_CONTROL_EXTRA (append postinst, prerm)
  Dev->>CPack: Build Debian package
  dpkg->>Post: Run postinst (configure/abort-*)
  Post->>Post: Execute placeholder post-install commands
  alt systemd available
    Post->>systemd: daemon-reload (quiet)
    Post->>systemd: restart FLB_OUT_NAME (best-effort)
  else no systemd
    Note right of Post: Skip daemon-reload/restart
  end

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Suggested reviewers

• niedbalski
• celalettin1286
• patrick-stephens

Poem

In burrows deep, I script and chime,
A postinst tune to mark install time.
CMake whispers, templates sing,
CPack bundles everything.
systemd yawns, reloads with grace—
hop, hop, restart the service in place. 🐇💿

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.
Title check	✅ Passed	The PR title 'build: execute daemon-reload and restart postinst in deb' is related to the main changes (Debian postinst modifications) but is vague about the specific nature of the changes and what 'execute' and 'restart postinst' refer to.

✨ Finishing touches

• 📝 Generate docstrings

---

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[coderabbitai]

Actionable comments posted: 3

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

CMakeLists.txt (1)

1488-1501: Broken packaging when FLB_RUN_LDCONFIG=OFF (unconditional prerm reference) + missing scripts dir + wrong var name for template.

• prerm is always appended (Line 1500), but only created when FLB_RUN_LDCONFIG is ON.
• ${PROJECT_BINARY_DIR}/scripts/ may not exist before file(WRITE) and configure_file, causing failures.
• Variable name should match postinst.in’s @LDCONFIG_POSTINST_CMDS@.

Fix all in one go:

Apply this diff:

-  set(LDCONFIG_SCRIPT_CMDS "")
-  if(FLB_RUN_LDCONFIG)
-    set(LDCONFIG_DIR ${FLB_INSTALL_LIBDIR})
-    set(LDCONFIG_SCRIPT_CMDS "
+  # Ensure scripts directory exists for generated maintainer scripts
+  file(MAKE_DIRECTORY "${PROJECT_BINARY_DIR}/scripts")
+
+  # Content injected into postinst when ldconfig is enabled
+  set(LDCONFIG_POSTINST_CMDS "")
+  if(FLB_RUN_LDCONFIG)
+    set(LDCONFIG_DIR "${FLB_INSTALL_LIBDIR}")
+    set(LDCONFIG_POSTINST_CMDS "
 mkdir -p /etc/ld.so.conf.d
 echo \"${LDCONFIG_DIR}\" > /etc/ld.so.conf.d/libfluent-bit.conf
 ldconfig
     ")
-    file(WRITE ${PROJECT_BINARY_DIR}/scripts/prerm "
+    file(WRITE "${PROJECT_BINARY_DIR}/scripts/prerm" "
 rm -f -- /etc/ld.so.conf.d/libfluent-bit.conf
 ldconfig
     ")
-    list(APPEND CPACK_DEBIAN_RUNTIME_PACKAGE_CONTROL_EXTRA "${PROJECT_BINARY_DIR}/scripts/postinst;${PROJECT_BINARY_DIR}/scripts/prerm")
+    # Ensure executable bit for dpkg maintainer script
+    execute_process(COMMAND "${CMAKE_COMMAND}" -E chmod +x "${PROJECT_BINARY_DIR}/scripts/prerm")
+    list(APPEND CPACK_DEBIAN_RUNTIME_PACKAGE_CONTROL_EXTRA "${PROJECT_BINARY_DIR}/scripts/prerm")
   endif(FLB_RUN_LDCONFIG)

🧹 Nitpick comments (2)

cpack/debian/postinst.in (2)

4-9: Limit service actions to configure; avoid try-restart on abort- phases.*

Running daemon-reload/try-restart during abort-* is unnecessary and unexpected for Debian maintainer scripts. Keep these to the configure phase.

Apply this diff:

-if [ "$1" = "configure" ] || [ "$1" = "abort-upgrade" ] || [ "$1" = "abort-deconfigure" ] || [ "$1" = "abort-remove" ] ; then
+if [ "$1" = "configure" ] ; then
     if [ -d /run/systemd/system ]; then
         systemctl --system daemon-reload >/dev/null || true
         systemctl try-restart @[email protected] >/dev/null || true
     fi
 fi

---

5-8: Prefer deb-systemd-invoke to systemctl for maintainer scripts.

deb-systemd-invoke handles non-systemd environments and policy nuances better than calling systemctl directly.

Consider:

-        systemctl --system daemon-reload >/dev/null || true
-        systemctl try-restart @[email protected] >/dev/null || true
+        if command -v deb-systemd-invoke >/dev/null 2>&1; then
+            deb-systemd-invoke --system daemon-reload >/dev/null || true
+            deb-systemd-invoke try-restart @[email protected] >/dev/null || true
+        else
+            systemctl --system daemon-reload >/dev/null || true
+            systemctl try-restart @[email protected] >/dev/null || true
+        fi

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between d21e8de and 3c3a743.

📒 Files selected for processing (2)

• CMakeLists.txt (2 hunks)
• cpack/debian/postinst.in (1 hunks)

🧰 Additional context used

🧠 Learnings (4)

📚 Learning: 2025-09-14T17:23:01.225Z

Learnt from: aminvakil
PR: fluent/fluent-bit#10844
File: src/CMakeLists.txt:664-668
Timestamp: 2025-09-14T17:23:01.225Z
Learning: Many popular Debian packages like nginx and fail2ban install both init.d scripts and systemd services simultaneously, following standard Debian packaging practices where systemd automatically prefers the native service file over the SysV init script when both are present.

Applied to files:

• CMakeLists.txt

📚 Learning: 2025-08-31T12:46:11.940Z

Learnt from: ThomasDevoogdt
PR: fluent/fluent-bit#9277
File: .github/workflows/pr-compile-check.yaml:147-151
Timestamp: 2025-08-31T12:46:11.940Z
Learning: In fluent-bit CMakeLists.txt, the system library preference flags are defined as FLB_PREFER_SYSTEM_LIB_ZSTD and FLB_PREFER_SYSTEM_LIB_KAFKA with the FLB_ prefix.

Applied to files:

• CMakeLists.txt

📚 Learning: 2025-08-31T12:46:11.940Z

Learnt from: ThomasDevoogdt
PR: fluent/fluent-bit#9277
File: .github/workflows/pr-compile-check.yaml:147-151
Timestamp: 2025-08-31T12:46:11.940Z
Learning: In fluent-bit, the correct CMake flag for using system librdkafka is `FLB_PREFER_SYSTEM_LIB_KAFKA=ON`.

Applied to files:

• CMakeLists.txt

📚 Learning: 2025-09-14T09:46:09.531Z

Learnt from: aminvakil
PR: fluent/fluent-bit#10844
File: conf/fluent-bit:13-15
Timestamp: 2025-09-14T09:46:09.531Z
Learning: For fluent-bit Debian packaging, /opt/fluent-bit/bin/ is the appropriate installation path since the package may be installed from non-official Debian sources, making /opt compliant with FHS for optional software packages.

Applied to files:

• CMakeLists.txt

[github-actions]

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