OK, então acontece que um colega acidentalmente executou um comando de desligamento atrasado no terminal errado. Estou aceitando essa resposta, mas ainda seria interessante se houvesse uma maneira de descobrir isso no sistema.
Esta manhã minha máquina rodando o Fedora 22 estava em estado de desligamento mostrando, IIRC, algo como o seguinte, em tela cheia branca em terminal preto:
[Rebooting] ...
System halted.
Depois de segurar o botão liga / desliga e reiniciar, estou procurando determinar o que causou essa reinicialização indesejada. Olhando para alguns logs, eu sei que foi até pelo menos às 14:00 de domingo. Existe mais informação disponível em algum lugar do sistema? Qual processo iniciou o desligamento? Foi um kernel panic, um script, qual usuário, etc?
Não conheço nenhum problema de hardware ou procedimentos automáticos de atualização. É um computador desktop de alguns anos que também executa alguns trabalhos cron. Ele foi recentemente atualizado para um Fedora 22 limpo e estava funcionando bem até agora.
Usando sudo journalctl -b -1 , posso ver o desligamento do sistema em torno de 17:36, seguido pela seqüência de desligamento precisamente 5 minutos depois.
Há também o NetworkManager verificando a conectividade e falhando repetidamente ao mesmo tempo. Aqui está um extrato do log desse tempo:
Dec 20 17:20:49 <myhostname> NetworkManager[844]: <info> connectivity: check for uri 'http://fedoraproject.org/static/hotspot.txt' failed with 'Impossible de se connecter : Le réseau n'est pas accessible'
Dec 20 17:25:49 <myhostname> NetworkManager[844]: <info> connectivity: check for uri 'http://fedoraproject.org/static/hotspot.txt' failed with 'Impossible de se connecter : Le réseau n'est pas accessible'
Dec 20 17:30:49 <myhostname> NetworkManager[844]: <info> connectivity: check for uri 'http://fedoraproject.org/static/hotspot.txt' failed with 'Impossible de se connecter : Le réseau n'est pas accessible'
Dec 20 17:35:49 <myhostname> NetworkManager[844]: <info> connectivity: check for uri 'http://fedoraproject.org/static/hotspot.txt' failed with 'Impossible de se connecter : Le réseau n'est pas accessible'
Dec 20 17:36:53 <myhostname> systemd-shutdownd[16731]: Creating /run/nologin, blocking further logins...
Dec 20 17:40:49 <myhostname> NetworkManager[844]: <info> connectivity: check for uri 'http://fedoraproject.org/static/hotspot.txt' failed with 'Impossible de se connecter : Le réseau n'est pas accessible'
Dec 20 17:41:53 <myhostname> systemd[1]: Stopping Manage Sound Card State (restore and store)...
Dec 20 17:41:53 <myhostname> systemd[1]: Stopping LVM2 PV scan on device 8:2...
Dec 20 17:41:53 <myhostname> systemd[1]: Stopping Restore /run/initramfs on shutdown...
Dec 20 17:41:53 <myhostname> systemd[1]: Stopped Session c1 of user gdm.
... etc (shutdown)
Aqui está a saída do lspci:
00:00.0 Host bridge: Intel Corporation 5520/5500/X58 I/O Hub to ESI Port (rev 13)
00:01.0 PCI bridge: Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root Port 1 (rev 13)
00:03.0 PCI bridge: Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root Port 3 (rev 13)
00:07.0 PCI bridge: Intel Corporation 5520/5500/X58 I/O Hub PCI Express Root Port 7 (rev 13)
00:10.0 PIC: Intel Corporation 7500/5520/5500/X58 Physical and Link Layer Registers Port 0 (rev 13)
00:10.1 PIC: Intel Corporation 7500/5520/5500/X58 Routing and Protocol Layer Registers Port 0 (rev 13)
00:11.0 PIC: Intel Corporation 7500/5520/5500 Physical and Link Layer Registers Port 1 (rev 13)
00:11.1 PIC: Intel Corporation 7500/5520/5500 Routing & Protocol Layer Register Port 1 (rev 13)
00:14.0 PIC: Intel Corporation 7500/5520/5500/X58 I/O Hub System Management Registers (rev 13)
00:14.1 PIC: Intel Corporation 7500/5520/5500/X58 I/O Hub GPIO and Scratch Pad Registers (rev 13)
00:14.2 PIC: Intel Corporation 7500/5520/5500/X58 I/O Hub Control Status and RAS Registers (rev 13)
00:15.0 PIC: Intel Corporation 7500/5520/5500/X58 Trusted Execution Technology Registers (rev 13)
00:1a.0 USB controller: Intel Corporation 82801JI (ICH10 Family) USB UHCI Controller #4
00:1a.1 USB controller: Intel Corporation 82801JI (ICH10 Family) USB UHCI Controller #5
00:1a.2 USB controller: Intel Corporation 82801JI (ICH10 Family) USB UHCI Controller #6
00:1a.7 USB controller: Intel Corporation 82801JI (ICH10 Family) USB2 EHCI Controller #2
00:1b.0 Audio device: Intel Corporation 82801JI (ICH10 Family) HD Audio Controller
00:1c.0 PCI bridge: Intel Corporation 82801JI (ICH10 Family) PCI Express Root Port 1
00:1c.5 PCI bridge: Intel Corporation 82801JI (ICH10 Family) PCI Express Root Port 6
00:1d.0 USB controller: Intel Corporation 82801JI (ICH10 Family) USB UHCI Controller #1
00:1d.1 USB controller: Intel Corporation 82801JI (ICH10 Family) USB UHCI Controller #2
00:1d.2 USB controller: Intel Corporation 82801JI (ICH10 Family) USB UHCI Controller #3
00:1d.7 USB controller: Intel Corporation 82801JI (ICH10 Family) USB2 EHCI Controller #1
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 90)
00:1f.0 ISA bridge: Intel Corporation 82801JIR (ICH10R) LPC Interface Controller
00:1f.2 RAID bus controller: Intel Corporation SATA Controller [RAID mode]
01:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5764M Gigabit Ethernet PCIe (rev 10)
0f:00.0 VGA compatible controller: NVIDIA Corporation GF108GL [Quadro 600] (rev a1)
0f:00.1 Audio device: NVIDIA Corporation GF108 High Definition Audio Controller (rev a1)
37:05.0 FireWire (IEEE 1394): LSI Corporation FW322/323 [TrueFire] 1394a Controller (rev 70)
3f:00.0 Host bridge: Intel Corporation Xeon 5500/Core i7 QuickPath Architecture Generic Non-Core Registers (rev 05)
3f:00.1 Host bridge: Intel Corporation Xeon 5500/Core i7 QuickPath Architecture System Address Decoder (rev 05)
3f:02.0 Host bridge: Intel Corporation Xeon 5500/Core i7 QPI Link 0 (rev 05)
3f:02.1 Host bridge: Intel Corporation Xeon 5500/Core i7 QPI Physical 0 (rev 05)
3f:03.0 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller (rev 05)
3f:03.1 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Target Address Decoder (rev 05)
3f:03.4 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Test Registers (rev 05)
3f:04.0 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 0 Control Registers (rev 05)
3f:04.1 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 0 Address Registers (rev 05)
3f:04.2 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 0 Rank Registers (rev 05)
3f:04.3 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 0 Thermal Control Registers (rev 05)
3f:05.0 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 1 Control Registers (rev 05)
3f:05.1 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 1 Address Registers (rev 05)
3f:05.2 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 1 Rank Registers (rev 05)
3f:05.3 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 1 Thermal Control Registers (rev 05)
3f:06.0 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 2 Control Registers (rev 05)
3f:06.1 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 2 Address Registers (rev 05)
3f:06.2 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 2 Rank Registers (rev 05)
3f:06.3 Host bridge: Intel Corporation Xeon 5500/Core i7 Integrated Memory Controller Channel 2 Thermal Control Registers (rev 05)