.. _systemd_service_mask: ====================== Systemd Service Mask ====================== 我在 :ref:`jetson_nano_startup` 构建一个工作环境，采用 :ref:`networkmanager` 来实现无线网络配置。最近，我发现 :ref:`jetson_nano` 升级重启后，无线网络没有激活。 - 检查 :ref:`networkmanager` 服务:: systemctl status NetworkManager 输出显示服务没有启动:: ● NetworkManager.service - Network Manager Loaded: loaded (/lib/systemd/system/NetworkManager.service; masked; vendor preset: enabled) Active: inactive (dead) Docs: man:NetworkManager(8) - 启动服务:: systemctl start NetworkManager 可以看到服务能够正常启动，再次检查 ``systemctl status NetworkManager`` 也可以看到服务正常运行:: ● NetworkManager.service - Network Manager Loaded: loaded (/lib/systemd/system/NetworkManager.service; masked; vendor preset: enabled) Active: active (running) since Tue 2021-06-01 15:37:26 CST; 7s ago Docs: man:NetworkManager(8) Main PID: 27815 (NetworkManager) Tasks: 5 (limit: 4181) CGroup: /system.slice/NetworkManager.service ├─27815 /usr/sbin/NetworkManager --no-daemon └─28306 /sbin/dhclient -d -q -sf /usr/lib/NetworkManager/nm-dhcp-helper -pf /run/dhclient-wlan0.pid -lf /var/lib/NetworkManager/dhclient-da5a19b4-2088-49ae-990d-6461897ba47 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.2892] dhcp4 (wlan0): state changed unknown -> bound 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.2964] device (wlan0): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'managed') 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.2976] device (wlan0): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'managed') 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.2983] device (wlan0): state change: secondaries -> activated (reason 'none', sys-iface-state: 'managed') 6月 01 15:37:32 jetson dhclient[28306]: bound to 192.168.0.111 -- renewal in 1515 seconds. 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.3265] device (wlan0): Activation: successful, device activated. 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.3270] manager: startup complete 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.3288] dns-sd-resolved[0x5596424de0]: Failed: GDBus.Error:org.freedesktop.resolve1.LinkBusy: Link eth0 is managed. 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.3289] dns-sd-resolved[0x5596424de0]: Failed: GDBus.Error:org.freedesktop.resolve1.LinkBusy: Link eth0 is managed. 6月 01 15:37:32 jetson NetworkManager[27815]: [1622533052.3299] dns-sd-resolved[0x5596424de0]: Failed: GDBus.Error:org.freedesktop.resolve1.LinkBusy: Link eth0 is managed. - 但是服务无法激活:: systemctl enable NetworkManager 显示服务已经被屏蔽:: Failed to enable unit: Unit file /etc/systemd/system/NetworkManager.service is masked. Systemd Service Mask原因 ========================= systemd服务的所谓 ``mask`` 状态，实际上是 ``disable`` 的强化版本。当设置服务 ``disable`` 时，所有服务单元的软链接都被移除，但是如果配置成 ``mask`` 则单元被链接到 ``/dev/null`` - 通过以下命令检查unit文件状态:: systemctl list-unit-files 可以看到:: ... NetworkManager-dispatcher.service disabled NetworkManager-wait-online.service disabled NetworkManager.service masked ... - 检查unit，可以看到被软链接到 ``/dev/null`` :: ls -lh /etc/systemd/system/NetworkManager.service 显示:: lrwxrwxrwx 1 root root 9 6月 1 16:22 /etc/systemd/system/NetworkManager.service -> /dev/null - 注意到我采用了 :ref:`systemd_networkd` 管理了 ``eth0`` ，这导致两者存在冲突。所以关闭掉 ``systemd-networkd`` 之后再重新激活 ``NetworkManager`` :: systemctl stop systemd-networkd systemctl disable systemd-networkd 恢复被Mask的服务 ================== - systemdctl提供了一个 ``unmask`` 命令可以去除Mask:: systemctl unmask NetworkManger 提示信息:: Removed /etc/systemd/system/NetworkManager.service. - 然后可以enable该服务:: systemctl enable NetworkManager 显示:: Created symlink /etc/systemd/system/multi-user.target.wants/NetworkManager.service → /lib/systemd/system/NetworkManager.service. Created symlink /etc/systemd/system/dbus-org.freedesktop.nm-dispatcher.service → /lib/systemd/system/NetworkManager-dispatcher.service. - 启动了NetworkManager之后，可以看到 ``nmcli conn`` 显示其管理的网络连接:: nmcli conn 显示管理了无线，也管理了docker0的bridge网络:: NAME UUID TYPE DEVICE Wired connection 1 a94fa1de-b290-3b83-9f49-137981396543 ethernet eth0 docker0 0bdc7a88-3f72-438e-9674-0af8fc1af7db bridge docker0 office da5a19b4-2088-49ae-990d-6461897ba471 wifi wlan0 .. note:: 这里 ``docker0`` 的bridge如果没有启动，会导致docker无法正常工作，影响kubernetes工作。 参考 ========= - `Why are some systemd services in the “masked” state? `_