我最近将 Ubuntu 16 的服务器版本升级到 Lubuntu 18。我可以发现所有可用的 WiFi 网络，但我无法至少通过两个已知网络进行身份验证。我不确定系统是否有任何缓存的密码或与 Ubuntu 16 的网络配置冲突。下面是与此问题相关的一些相关日志。任何帮助表示赞赏。
Sep 15 19:05:14 rag-server NetworkManager[1240]: <warn> [1537034714.7054] dhcp4 (wlp2s0b1): request timed out
Sep 15 19:05:14 rag-server NetworkManager[1240]: <info> [1537034714.7055] dhcp4 (wlp2s0b1): state changed unknown -> timeout
Sep 15 19:05:14 rag-server NetworkManager[1240]: <info> [1537034714.7219] dhcp4 (wlp2s0b1): canceled DHCP transaction, DHCP client pid 7745
Sep 15 19:05:14 rag-server NetworkManager[1240]: <info> [1537034714.7219] dhcp4 (wlp2s0b1): state changed timeout -> done
Sep 15 19:05:14 rag-server NetworkManager[1240]: <info> [1537034714.7226] device (wlp2s0b1): state change: ip-config -> failed (reason 'ip-config-unavailable', sys-iface-state: 'managed')
Sep 15 19:05:14 rag-server NetworkManager[1240]: <warn> [1537034714.7245] device (wlp2s0b1): Activation: failed for connection 'rp'
Sep 15 19:05:14 rag-server NetworkManager[1240]: <info> [1537034714.7345] device (wlp2s0b1): state change: failed -> disconnected (reason 'none', sys-iface-state: 'managed')
Sep 15 19:05:14 rag-server avahi-daemon[1251]: Withdrawing address record for fe80::4201:5623:fc5d:1597 on wlp2s0b1.
Sep 15 19:05:14 rag-server avahi-daemon[1251]: Leaving mDNS multicast group on interface wlp2s0b1.IPv6 with address fe80::4201:5623:fc5d:1597.
Sep 15 19:05:14 rag-server avahi-daemon[1251]: Interface wlp2s0b1.IPv6 no longer relevant for mDNS.
Sep 15 19:05:14 rag-server kernel: [ 1896.027008] wlp2s0b1: deauthenticating from 64:d1:54:63:f2:32 by local choice (Reason: 3=DEAUTH_LEAVING)
Sep 15 19:05:14 rag-server kernel: [ 1896.028874] brcmsmac bcma0:1: brcmsmac: brcms_ops_bss_info_changed: disassociated
Sep 15 19:05:14 rag-server kernel: [ 1896.028885] brcmsmac bcma0:1: brcms_ops_bss_info_changed: qos enabled: false (implement)
Sep 15 19:05:14 rag-server wpa_supplicant[1250]: wlp2s0b1: CTRL-EVENT-DISCONNECTED bssid=64:d1:54:63:f2:32 reason=3 locally_generated=1
Sep 15 19:05:14 rag-server wpa_supplicant[1250]: wlp2s0b1: CTRL-EVENT-REGDOM-CHANGE init=CORE type=WORLD
Sep 15 19:05:14 rag-server NetworkManager[1240]: <warn> [1537034714.7497] sup-iface[0x563414f86190,wlp2s0b1]: connection disconnected (reason -3)
Sep 15 19:05:14 rag-server NetworkManager[1240]: <info> [1537034714.7499] device (wlp2s0b1): supplicant interface state: completed -> disconnected