Cloud not start the snap application

The problem has been solved. Move snap packages to another location/directory

on centos7, the first time snap application can be successfully launched, but the second time it can not be started, the error message is below. Any ideas?

$ snap run hello
cannot find mount entry for snap core revision 7713

by the way, when i installed snapd, i executed the following commands

# ln -s /var/lib /usr/var/lib
$ snap version
snap    2.39.2-1.el7
snapd   2.39.2-1.el7
series  16
centos  7
kernel  3.10.0-1062.1.1.el7.x86_64
$ snap list
Name        Version   Rev   Tracking  Publisher   Notes
core        16-2.41   7713  stable    canonical✓  core
core18      20190904  1144  stable    canonical✓  base
hello       2.10      38    stable    canonical✓  -
# df -h |grep snap
/dev/loop0      128K  128K     0  100% /usr/var/lib/snapd/snap/hello/38
/dev/loop1       90M   90M     0  100% /usr/var/lib/snapd/snap/core/7713
/dev/loop2       55M   55M     0  100% /usr/var/lib/snapd/snap/core18/1144
# systemctl status snapd
● snapd.service - Snappy daemon
   Loaded: loaded (/usr/lib/systemd/system/snapd.service; disabled; vendor preset: disabled)
  Drop-In: /etc/systemd/system/snapd.service.d
   Active: active (running) since 五 2019-09-27 07:21:28 CST; 38min ago
 Main PID: 21284 (snapd)
    Tasks: 57
   Memory: 28.3M
   CGroup: /system.slice/snapd.service
           └─21284 /usr/libexec/snapd/snapd

9月 27 07:21:28 xeon-e5 systemd[1]: Starting Snappy daemon...
9月 27 07:21:28 xeon-e5 snapd[21284]: AppArmor status: apparmor not enabled
9月 27 07:21:28 xeon-e5 snapd[21284]: daemon.go:379: started snapd/2.39.2-1.el7 (series 16; classic; devmode) centos/7 (amd64) linux/3.10.0-1062.1.1.el7.x86_6.
9月 27 07:21:28 xeon-e5 systemd[1]: Started Snappy daemon.