/init: line 7: can't open /dev/sdb: No medium found
/init: line 7: can't open /dev/sdb: No medium found
dbus-daemon[791]: [session uid=999 pid=791] Activating service name='org.gtk.vfs.Daemon' requested by ':1.0' (uid=999 pid=792 comm="" label="unconfined")
dbus-daemon[791]: [session uid=999 pid=791] Successfully activated service 'org.gtk.vfs.Daemon'
dbus-daemon[791]: [session uid=999 pid=791] Activating service name='org.gtk.vfs.Metadata' requested by ':1.0' (uid=999 pid=792 comm="" label="unconfined")
fuse: device not found, try 'modprobe fuse' first
dbus-daemon[791]: [session uid=999 pid=791] Successfully activated service 'org.gtk.vfs.Metadata'

(gvfsd-metadata:803): GUdev-CRITICAL **: 03:09:00.098: g_udev_device_has_property: assertion 'G_UDEV_IS_DEVICE (device)' failed

(gvfsd-metadata:803): GUdev-CRITICAL **: 03:09:00.098: g_udev_device_has_property: assertion 'G_UDEV_IS_DEVICE (device)' failed
A connection to the bus can't be made
Using CD-ROM mount point /cdrom/
Identifying... [efe86f4d875231f119e1e7b952fa1be5-2]
Scanning disc for index files...
Found 4 package indexes, 0 source indexes, 0 translation indexes and 1 signatures
Found label 'Ubuntu-MATE 18.04 LTS _Bionic Beaver_ - Release amd64 (20180425.1)'
This disc is called: 
'Ubuntu-MATE 18.04 LTS _Bionic Beaver_ - Release amd64 (20180425.1)'
Copying package lists...gpgv: Signature made Wed Apr 25 22:52:25 2018 UTC
gpgv:                using RSA key D94AA3F0EFE21092
gpgv: Good signature from "Ubuntu CD Image Automatic Signing Key (2012) <cdimage@ubuntu.com>"

Reading Package Indexes... 0%

Reading Package Indexes... Done
Writing new source list
Source list entries for this disc are:
deb cdrom:[Ubuntu-MATE 18.04 LTS _Bionic Beaver_ - Release amd64 (20180425.1)]/ bionic main multiverse restricted universe
Repeat this process for the rest of the CDs in your set.