我的电脑屏幕亮度发生了变化，几个小时后它自动关机了。我查看了系统日志，发现了以下屏幕亮度信息：
Mar 26 09:17:01 My-PC CRON[12162]: pam_unix(cron:session): session closed for user root
Mar 26 09:51:10 My-PC pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Mar 26 09:51:10 My-PC pkexec: pam_systemd(polkit-1:session): Cannot create session: Already running in a session
**Mar 26 09:51:10 My-PC pkexec[12500]: computer: Executing command [USER=root] [TTY=unknown] [CWD=/home/computer] [COMMAND=/usr/lib/unity-settings-daemon/usd-backlight-helper --set-brightness 158]**
Mar 26 10:17:01 My-PC CRON[12756]: pam_unix(cron:session): session opened for user root by (uid=0)
Mar 26 10:17:01 My-PC CRON[12756]: pam_unix(cron:session): session closed for user root
我搜索了 pkexec[12500]，发现 pkexec 允许授权用户以其他用户身份执行 PROGRAM。这是什么意思？这个命令会被黑客使用吗？
至于关闭，我发现这是关闭时 sys.log：
Mar 26 12:17:01 My-PC CRON[13894]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Mar 26 12:57:22 My-PC kernel: [71651.239315] [UFW BLOCK] IN= OUT=anbox0 SRC=fe80:0000:0000:0000:c8a0:59ff:feaa:bfbf DST=ff02:0000:0000:0000:0000:0000:0000:00fb LEN=166 TC=0 HOPLIMIT=255 FLOWLBL=510582 PROTO=UDP SPT=5353 DPT=5353 LEN=126
Mar 26 12:57:22 My-PC kernel: [71651.239446] [UFW BLOCK] IN= OUT=anbox0 SRC=192.168.250.1 DST=224.0.0.251 LEN=146 TOS=0x00 PREC=0x00 TTL=255 ID=13205 DF PROTO=UDP SPT=5353 DPT=5353 LEN=126
Mar 26 13:00:14 My-PC systemd[1]: Closed Load/Save RF Kill Switch Status /dev/rfkill Watch.
Mar 26 13:00:14 My-PC systemd[1]: Stopping Firmware update daemon...
Mar 26 13:00:14 My-PC systemd[1]: Stopping ACPI event daemon...
Mar 26 13:00:14 My-PC systemd[1]: Stopping Session c2 of user computer.
Mar 26 13:00:14 My-PC systemd[1]: Stopping User Manager for UID 1000...
Mar 26 13:00:14 My-PC systemd[1]: Stopped target Bluetooth.
Mar 26 13:00:14 My-PC systemd[1]: Stopped target Sound Card.
Mar 26 13:00:14 My-PC systemd[2008]: Stopped target Default.
Mar 26 13:00:14 My-PC systemd[2008]: Stopped target Basic System.
Mar 26 13:00:14 My-PC systemd[2008]: Stopped target Timers.
Mar 26 13:00:14 My-PC systemd[2008]: Stopped target Sockets.
Mar 26 13:00:14 My-PC pulseaudio[2351]: [pulseaudio] module-x11-publish.c: PulseAudio information vanished from X11!
Mar 26 13:00:14 My-PC systemd[2008]: Stopped target Paths.
Mar 26 13:00:14 My-PC systemd[2008]: Reached target Shutdown.
Mar 26 13:00:14 My-PC systemd[2008]: Starting Exit the Session...
Mar 26 13:00:14 My-PC systemd[1]: Stopping RealtimeKit Scheduling Policy Service...
Mar 26 13:00:14 My-PC bluetoothd[1234]: Terminating
Mar 26 13:00:14 My-PC systemd[1]: Stopping Manage, Install and Generate Color Profiles...
Mar 26 13:00:14 My-PC systemd[1]: Stopped Stop ureadahead data collection 45s after completed startup.
Mar 26 13:00:14 My-PC systemd[1]: Stopping Bluetooth service...
Mar 26 13:00:14 My-PC systemd[1]: Stopped target Graphical Interface.
Mar 26 13:00:14 My-PC systemd[1]: Stopping Light Display Manager...
Mar 26 13:00:14 My-PC systemd[1]: Stopped target Timers.
Mar 26 13:00:14 My-PC systemd[1]: Stopped Daily apt upgrade and clean activities.
Mar 26 13:00:14 My-PC systemd[1]: Stopped Daily apt download activities.
Mar 26 13:00:14 My-PC systemd[1]: Stopped Daily Cleanup of Temporary Directories.
Mar 26 13:00:14 My-PC systemd[1]: Stopped target Multi-User System.
Mar 26 13:00:14 My-PC systemd[1]: Stopping Service for snap application anbox.container-manager...
Mar 26 13:00:14 My-PC systemd[1]: Stopping LSB: Record successful boot for GRUB...
Mar 26 13:00:14 My-PC bluetoothd[1234]: Endpoint unregistered: sender=:1.70 path=/MediaEndpoint/A2DPSource
Mar 26 13:00:14 My-PC systemd[1]: Stopping crash report submission daemon...
Mar 26 13:00:14 My-PC bluetoothd[1234]: Endpoint unregistered: sender=:1.70 path=/MediaEndpoint/A2DPSink
Mar 26 13:00:14 My-PC systemd[1]: Stopping LSB: automatic crash report generation...
Mar 26 13:00:14 My-PC rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="1252" x-info="http://www.rsyslog.com"] exiting on signal 15.
你能解释一下这些消息的含义吗：
Mar 26 12:17:01 My-PC CRON[13894]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Mar 26 12:57:22 My-PC kernel: [71651.239315] [UFW BLOCK] IN= OUT=anbox0 SRC=fe80:0000:0000:0000:c8a0:59ff:feaa:bfbf DST=ff02:0000:0000:0000:0000:0000:0000:00fb LEN=166 TC=0 HOPLIMIT=255 FLOWLBL=510582 PROTO=UDP SPT=5353 DPT=5353 LEN=126
这是关于 anbox 的吗？我按照网上的指南安装了它。为什么它会尝试在线通信？我如何阻止它自行启动？
在 auth.log 中我发现了这一点：
Mar 26 13:00:14 My-PC systemd-logind[1265]: System is powering down.
你能说出这是什么意思吗？
**Mar 26 13:00:14 My-PC polkitd(authority=local): Unregistered Authentication Agent for unix-session:c2 (system bus name :1.75, object path /org/gnome/PolicyKit1/AuthenticationAgent, locale en_US.UTF-8) (disconnected from bus)**