第一步是 -sudo yum install snapd
这似乎工作正常 下载依赖项和所有内容，安装完成
安装版本：snapd.x86_64 0：2.45-1.el7
第二步是 -sudo systemctl enable --now snapd.socket
输出为> 从/etc/systemd/system/sockets.target.wants/snapd.socket 到/usr/lib/systemd/system/snapd.socket 创建的符号链接。
现在检查状态 -sudo systemctl status snapd给出：
● snapd.service - Snap Daemon
Loaded: loaded (/usr/lib/systemd/system/snapd.service; disabled; vendor preset: disabled)
Active: failed (Result: start-limit) since Mon 2020-12-07 11:17:28 IST; 16min ago
Main PID: 5726 (code=exited, status=1/FAILURE)
systemd[1]: snapd.service holdoff time over, scheduling restart.
systemd[1]: Stopped Snap Daemon.
systemd[1]: start request repeated too quickly for snapd.service
systemd[1]: Failed to start Snap Daemon.
systemd[1]: Unit snapd.service entered failed state.
systemd[1]: Triggering OnFailure= dependencies of snapd.service.
systemd[1]: snapd.service failed.
systemd[1]: start request repeated too quickly for snapd.service
systemd[1]: Failed to start Snap Daemon.
systemd[1]: snapd.service failed.
尝试过可能的解决方案 - 1)清除后重新安装，2) 再次重新启动后启用套接字和服务。
journalctl -u snapd.service输出：
-- Logs begin at Wed 2020-12-09 11:21:36 IST, end at Thu 2020-12-17 12:40:16 IST. --
Dec 17 12:36:45 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:36:45 whf00jfw snapd[4639]: AppArmor status: apparmor not enabled
Dec 17 12:36:45 whf00jfw snapd[4639]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:36:46 whf00jfw snapd[4639]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:36:46 whf00jfw snapd[4639]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:36:46 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:36:46 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:36:46 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:36:46 whf00jfw snapd[4673]: AppArmor status: apparmor not enabled
Dec 17 12:36:46 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:36:46 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:36:46 whf00jfw snapd[4673]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:36:46 whf00jfw snapd[4673]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:36:46 whf00jfw snapd[4673]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:36:46 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:36:46 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:36:46 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:36:46 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:36:46 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:36:46 whf00jfw snapd[4699]: AppArmor status: apparmor not enabled
Dec 17 12:36:46 whf00jfw snapd[4699]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:36:46 whf00jfw snapd[4699]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:36:46 whf00jfw snapd[4699]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:36:46 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:36:46 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:36:46 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:36:46 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:36:46 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:36:46 whf00jfw snapd[4745]: AppArmor status: apparmor not enabled
Dec 17 12:36:46 whf00jfw snapd[4745]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:36:46 whf00jfw snapd[4745]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:36:46 whf00jfw snapd[4745]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:36:46 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:36:46 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:36:46 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:36:46 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:36:47 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:36:47 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:36:47 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:36:47 whf00jfw snapd[4775]: AppArmor status: apparmor not enabled
Dec 17 12:36:47 whf00jfw snapd[4775]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:36:47 whf00jfw snapd[4775]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:36:47 whf00jfw snapd[4775]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:36:47 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:36:47 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:36:47 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:36:47 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:36:47 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:36:47 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:36:47 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:36:47 whf00jfw systemd[1]: start request repeated too quickly for snapd.service
Dec 17 12:36:47 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:36:47 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:36:47 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:36:47 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:36:47 whf00jfw systemd[1]: start request repeated too quickly for snapd.service
Dec 17 12:36:47 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:36:47 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:40:15 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:40:15 whf00jfw snapd[5826]: AppArmor status: apparmor not enabled
Dec 17 12:40:15 whf00jfw snapd[5826]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:40:15 whf00jfw snapd[5826]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:40:15 whf00jfw snapd[5826]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:40:15 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:40:15 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:40:15 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:40:15 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:40:15 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:40:15 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:40:15 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:40:15 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:40:15 whf00jfw snapd[5855]: AppArmor status: apparmor not enabled
Dec 17 12:40:15 whf00jfw snapd[5855]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:40:15 whf00jfw snapd[5855]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:40:15 whf00jfw snapd[5855]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:40:15 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:40:15 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:40:15 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:40:15 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:40:15 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:40:16 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:40:16 whf00jfw snapd[5952]: AppArmor status: apparmor not enabled
Dec 17 12:40:16 whf00jfw snapd[5952]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:40:16 whf00jfw snapd[5952]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:40:16 whf00jfw snapd[5952]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:40:16 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:40:16 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:40:16 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:40:16 whf00jfw snapd[6154]: AppArmor status: apparmor not enabled
Dec 17 12:40:16 whf00jfw snapd[6154]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:40:16 whf00jfw snapd[6154]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:40:16 whf00jfw snapd[6154]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:40:16 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:40:16 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:40:16 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: Starting Snap Daemon...
Dec 17 12:40:16 whf00jfw snapd[6260]: AppArmor status: apparmor not enabled
Dec 17 12:40:16 whf00jfw snapd[6260]: daemon.go:343: started snapd/2.45-1.el7 (series 16; classic; devmode) ol/7.6 (amd64) linux/4.14.35-1902.304.6.el7uek.
Dec 17 12:40:16 whf00jfw snapd[6260]: daemon.go:436: adjusting startup timeout by 30s (pessimistic estimate of 30s plus 5s per snap)
Dec 17 12:40:16 whf00jfw snapd[6260]: cannot run daemon: state startup errors: [cannot obtain snap-seccomp version information: fork/exec /usr/lib/snapd/snap
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service: main process exited, code=exited, status=1/FAILURE
Dec 17 12:40:16 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:40:16 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service holdoff time over, scheduling restart.
Dec 17 12:40:16 whf00jfw systemd[1]: Stopped Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: start request repeated too quickly for snapd.service
Dec 17 12:40:16 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: Unit snapd.service entered failed state.
Dec 17 12:40:16 whf00jfw systemd[1]: Triggering OnFailure= dependencies of snapd.service.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service failed.
Dec 17 12:40:16 whf00jfw systemd[1]: start request repeated too quickly for snapd.service
Dec 17 12:40:16 whf00jfw systemd[1]: Failed to start Snap Daemon.
Dec 17 12:40:16 whf00jfw systemd[1]: snapd.service failed.
这似乎是一个不使用AppArmor(OL，CentOS，RHEL)的操作系统不支持严格限制的问题。需要采取一些步骤才能使其发挥作用。您是否创建了符号链接？
sudo ln -s /var/lib/snapd/snap /snap
这对我有用：
sudo yum install snapd
sudo ln -s /var/lib/snapd/snap /snap
sudo systemctl enable --now snapd.socket
sudo systemctl restart snapd
<restart session>
sudo snap install firefox
sudo snap install --classic nano
只是想对此进行注释，因为它是此错误消息的最佳结果之一。我遇到了完全相同的错误，但能够通过尝试手动运行 snapd 找到更多详细信息，揭示了(在我的情况下)与已经过时的 snapd-seccomp 相关的问题。
运行"yum update libseccomp"解决了问题，并允许成功安装快照。