stdin: Not a typewriter /init: line 49: can't open /dev/sdf: No medium found /init: line 49: can't open /dev/sdf: No medium found /init: line 49: can't open /dev/sdg: No medium found /init: line 49: can't open /dev/sdg: No medium found /init: line 49: can't open /dev/sdh: No medium found /init: line 49: can't open /dev/sdh: No medium found /init: line 49: can't open /dev/sr0: No medium found /init: line 49: can't open /dev/sr0: No medium found stdin: Not a typewriter /init: line 49: can't open /dev/sdf: No medium found /init: line 49: can't open /dev/sdf: No medium found /init: line 49: can't open /dev/sdg: No medium found /init: line 49: can't open /dev/sdg: No medium found /init: line 49: can't open /dev/sdh: No medium found /init: line 49: can't open /dev/sdh: No medium found passwd: password expiry information changed. dbus-daemon[1549]: [session uid=999 pid=1549] Activating service name='org.gtk.vfs.Daemon' requested by ':1.0' (uid=999 pid=1550 comm="" label="unconfined") dbus-daemon[1549]: [session uid=999 pid=1549] Successfully activated service 'org.gtk.vfs.Daemon' dbus-daemon[1549]: [session uid=999 pid=1549] Activating service name='org.gtk.vfs.Metadata' requested by ':1.0' (uid=999 pid=1550 comm="" label="unconfined") fuse: device not found, try 'modprobe fuse' first dbus-daemon[1549]: [session uid=999 pid=1549] Successfully activated service 'org.gtk.vfs.Metadata' A connection to the bus can't be made Using CD-ROM mount point /cdrom/ Identifying... [01c5ded0e4d3639588aec21c38fdf8b8-2] Scanning disc for index files... Found 6 package indexes, 0 source indexes, 0 translation indexes and 2 signatures Found label 'Xubuntu 20.04.1 LTS _Focal Fossa_ - Release amd64 (20200731)' This disc is called: 'Xubuntu 20.04.1 LTS _Focal Fossa_ - Release amd64 (20200731)' Copying package lists...gpgv: Signature made Tue Jul 19 21:27:12 2016 UTC gpgv: using DSA key 46181433FBB75451 gpgv: Can't check signature: No public key Sub-process apt-key returned an error code (2)gpgv: Signature made Fri Jul 31 16:47:18 2020 UTC gpgv: using RSA key 843938DF228D22F7B3742BC0D94AA3F0EFE21092 gpgv: Good signature from "Ubuntu CD Image Automatic Signing Key (2012) " Reading Package Indexes... 0% Reading Package Indexes... Error! Writing new source list Source list entries for this disc are: deb cdrom:[Xubuntu 20.04.1 LTS _Focal Fossa_ - Release amd64 (20200731)]/ focal main multiverse restricted universe deb cdrom:[Xubuntu 20.04.1 LTS _Focal Fossa_ - Release amd64 (20200731)]/ xenial main restricted Repeat this process for the rest of the CDs in your set. E: Sub-process gpgv returned an error code (2) W: Signature verification failed for: /cdrom/dists/xenial/Release.gpg