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new a54a503 system-log: Start even if #:kernel-log-file cannot be opened.
a54a503 is described below
commit a54a503b01f9da4f6fb49d736dcf90da0fe51f1b
Author: Ludovic Courtès <l...@gnu.org>
AuthorDate: Wed May 7 00:06:15 2025 +0200
system-log: Start even if #:kernel-log-file cannot be opened.
Partly fixes <https://issues.guix.gnu.org/77578>.
Previously ‘system-log’ would fail to start if it could not
open #:kernel-log-file. This is unwise because in practice it would
prevent most other system services from starting. Furthermore,
on Linux /proc/kmsg is typically inaccessible in containers, so
gracefully handling it makes more sense.
* modules/shepherd/service/system-log.scm (system-log-service)
[maybe-kernel-log-port]: New procedure.
Use it.
* tests/services/system-log.sh: Add test where #:kernel-log-file is
inaccessible.
* NEWS: Update.
Reported-by: Oleg Pykhalov <go.wig...@gmail.com>
---
NEWS | 11 +++++++++
modules/shepherd/service/system-log.scm | 44 +++++++++++++++++++++------------
tests/services/system-log.sh | 25 +++++++++++++++++++
3 files changed, 64 insertions(+), 16 deletions(-)
diff --git a/NEWS b/NEWS
index cfc27aa..1022b7e 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,17 @@ Please send Shepherd bug reports to bug-g...@gnu.org.
When using the ‘system-log’ service, ‘herd status system-log’ now shows the
socket(s) it is listening to and the kernel log file it is reading (if any).
+** ‘system-log’ starts even if #:kernel-log-file is inaccessible
+ (<https://issues.guix.gnu.org/77578>)
+
+It used to be that ‘system-log’ would fail to start if the file specified as
+#:kernel-log-file was inaccessible. This was unwise because that would then
+typically prevent most system services from starting; also, on Linux, the
+default #:kernel-log-file is /proc/kmsg, and that is inaccessible within
+containers.
+
+Failure to open #:kernel-log-file is now logged but is non-fatal.
+
** ‘system-log’ service reads /dev/klog on the Hurd
(<https://issues.guix.gnu.org/77634>)
diff --git a/modules/shepherd/service/system-log.scm
b/modules/shepherd/service/system-log.scm
index 890a0f5..435949c 100644
--- a/modules/shepherd/service/system-log.scm
+++ b/modules/shepherd/service/system-log.scm
@@ -481,31 +481,43 @@ for a format identical to that of traditional syslogd
implementations.
Keep up to @var{history-size} messages in memory for the purposes of allowing
users to view recent messages without opening various files."
+ (define (maybe-kernel-log-port)
+ (catch 'system-error
+ (lambda ()
+ (open kernel-log-file
+ (logior O_RDONLY O_NONBLOCK O_CLOEXEC)))
+ (lambda args
+ ;; If KERNEL-LOG-FILE cannot be opened, dismiss it instead of failing
+ ;; to start since that could prevent many system services from
+ ;; starting (useful for example in Linux containers where /proc/kmsg
+ ;; is not accessible).
+ (local-output (l10n "Dismissing kernel log '~a': ~a.")
+ kernel-log-file
+ (strerror (system-error-errno args)))
+ #f)))
+
(define this-system-log
(service provision
#:requirement requirement
#:start (lambda ()
- (let ((channel (make-channel))
- (ports (append (open-sockets sources)
- (if kernel-log-file
- (list (open kernel-log-file
- (logior O_RDONLY
- O_NONBLOCK
-
O_CLOEXEC)))
- '())))
- (dispatcher (spawn-log-dispatcher
message-destination
-
#:max-silent-time
- max-silent-time
- #:history-size
- history-size
- #:date-format
- date-format)))
+ (let* ((channel (make-channel))
+ (klog (and kernel-log-file
+ (maybe-kernel-log-port)))
+ (ports (append (open-sockets sources)
+ (if klog (list klog) '())))
+ (dispatcher (spawn-log-dispatcher
message-destination
+
#:max-silent-time
+ max-silent-time
+ #:history-size
+ history-size
+ #:date-format
+ date-format)))
(register-service-logger this-system-log dispatcher)
(spawn-fiber
(lambda ()
(run-system-log channel ports dispatcher)))
(system-log channel ports dispatcher
- sources kernel-log-file)))
+ sources (and klog kernel-log-file))))
#:stop (lambda (system-log)
(let ((reply (make-channel)))
(put-message (system-log-channel system-log)
diff --git a/tests/services/system-log.sh b/tests/services/system-log.sh
index 047b9dd..5bc8116 100644
--- a/tests/services/system-log.sh
+++ b/tests/services/system-log.sh
@@ -248,6 +248,31 @@ do
test -f "$file"
done
+$herd stop system-log
+
+# Check that an inaccessible #:kernel-log-file does not prevent 'system-log'
+# from starting.
+
+cat > "$conf" <<EOF
+(use-modules (shepherd service system-log)
+ (shepherd endpoints)
+ (srfi srfi-19))
+
+(define %endpoints
+ (list (endpoint (make-socket-address AF_UNIX "$syslog_socket")
+ #:style SOCK_DGRAM)))
+
+(register-services
+ (list (system-log-service %endpoints
+ #:kernel-log-file "/does/not/exist")))
+EOF
+
+$herd load root "$conf"
+$herd start system-log
+$herd status system-log | grep "$syslog_socket"
+if $herd status system-log | grep "/does/not/exist"; then false; else true; fi
+grep "Dismissing kernel log.*/does/not/exist" "$log"
+
$herd stop root
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