启动后，无论是否插入电缆，都没有 eth0 设备！
/var/log/syslog 中没有任何内容 – 没有关于此接口的任何错误。
$ rfkill list
0: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no
1: phy1: Wireless LAN
Soft blocked: no
Hard blocked: no
2: hci0: Bluetooth
Soft blocked: no
Hard blocked: no
在 /etc/network/interfaces
什么都没有，只有注释行。
/etc/dhcpcd.conf 中也没有任何内容
在 /etc/default/networking
#CONFIGURE_INTERFACES=yes
#EXCLUDE_INTERFACES=
#VERBOSE=no
令我困惑的是，我有另一个具有相同选项（网络/接口，dhcpcd.conf）的 Pi，但另一个 pi 在启动时为其 eth0 供电并自动分配链接本地 ip（169.254）
有问题的 Pi 似乎根本没有与 eth0 交互。
您能给我什么线索，在哪里寻找这个问题？
dhcpcd 的状态
dhcpcd.service - dhcpcd on all interfaces
Loaded: loaded (/lib/systemd/system/dhcpcd.service; disabled; vendor preset: enabled)
Active: inactive (dead)
杂志：
-- Logs begin at Thu 2016-11-03 17:16:43 UTC, end at Thu 2019-08-01 14:00:02 UTC. --
Aug 01 13:56:01 wso-samsung-01 CRON[4481]: pam_unix(cron:session): session opened for user root by (uid=0)
Aug 01 13:56:01 wso-samsung-01 CRON[4485]: (root) CMD (/opt/check_lan/check_lan.sh >/dev/null)
Aug 01 13:56:04 wso-samsung-01 root[4492]: Network is up; clearing flag ...
Aug 01 13:56:04 wso-samsung-01 sudo[4493]: root : TTY=unknown ; PWD=/root ; USER=root ; COMMAND=/bin/rm -f /opt/check_lan/stuck.fflg
Aug 01 13:56:04 wso-samsung-01 sudo[4493]: pam_unix(sudo:session): session opened for user root by (uid=0)
Aug 01 13:56:04 wso-samsung-01 sudo[4493]: pam_unix(sudo:session): session closed for user root
Aug 01 13:56:04 wso-samsung-01 CRON[4481]: pam_unix(cron:session): session closed for user root
Aug 01 13:57:01 wso-samsung-01 CRON[4580]: pam_unix(cron:session): session opened for user root by (uid=0)
Aug 01 13:57:01 wso-samsung-01 CRON[4584]: (root) CMD (/opt/check_lan/check_lan.sh >/dev/null)
Aug 01 13:57:04 wso-samsung-01 root[4591]: Network is up; clearing flag ...
Aug 01 13:57:04 wso-samsung-01 sudo[4592]: root : TTY=unknown ; PWD=/root ; USER=root ; COMMAND=/bin/rm -f /opt/check_lan/stuck.fflg
Aug 01 13:57:04 wso-samsung-01 sudo[4592]: pam_unix(sudo:session): session opened for user root by (uid=0)
Aug 01 13:57:04 wso-samsung-01 sudo[4592]: pam_unix(sudo:session): session closed for user root
Aug 01 13:57:04 wso-samsung-01 CRON[4580]: pam_unix(cron:session): session closed for user root
Aug 01 13:58:01 wso-samsung-01 CRON[4681]: pam_unix(cron:session): session opened for user root by (uid=0)
Aug 01 13:58:01 wso-samsung-01 CRON[4685]: (root) CMD (/opt/check_lan/check_lan.sh >/dev/null)
Aug 01 13:58:08 wso-samsung-01 root[4693]: Network is up; clearing flag ...
Aug 01 13:58:08 wso-samsung-01 sudo[4694]: root : TTY=unknown ; PWD=/root ; USER=root ; COMMAND=/bin/rm -f /opt/check_lan/stuck.fflg
Aug 01 13:58:08 wso-samsung-01 sudo[4694]: pam_unix(sudo:session): session opened for user root by (uid=0)
Aug 01 13:58:08 wso-samsung-01 sudo[4694]: pam_unix(sudo:session): session closed for user root
Aug 01 13:58:08 wso-samsung-01 CRON[4681]: pam_unix(cron:session): session closed for user root
Aug 01 13:58:16 wso-samsung-01 sshd[4651]: Accepted password for pi from ::1 port 34710 ssh2
Aug 01 13:58:16 wso-samsung-01 sshd[4651]: pam_unix(sshd:session): session opened for user pi by (uid=0)
Aug 01 13:58:16 wso-samsung-01 systemd-logind[373]: New session c5 of user pi.
Aug 01 13:58:16 wso-samsung-01 systemd[1]: Started Session c5 of user pi.
Aug 01 13:58:26 wso-samsung-01 dhclient[563]: DHCPREQUEST of 172.27.0.129 on bat0 to 172.27.0.1 port 67
Aug 01 13:58:30 wso-samsung-01 dhclient[563]: DHCPACK of 172.27.0.129 from 172.27.0.1
Aug 01 13:58:30 wso-samsung-01 dhclient[563]: bound to 172.27.0.129 -- renewal in 262 seconds.
Aug 01 13:59:01 wso-samsung-01 CRON[4834]: pam_unix(cron:session): session opened for user root by (uid=0)
Aug 01 13:59:01 wso-samsung-01 CRON[4838]: (root) CMD (/opt/check_lan/check_lan.sh >/dev/null)
Aug 01 13:59:06 wso-samsung-01 root[4845]: Network is up; clearing flag ...
Aug 01 13:59:06 wso-samsung-01 sudo[4846]: root : TTY=unknown ; PWD=/root ; USER=root ; COMMAND=/bin/rm -f /opt/check_lan/stuck.fflg
Aug 01 13:59:06 wso-samsung-01 sudo[4846]: pam_unix(sudo:session): session opened for user root by (uid=0)