mount: mounting /dev/sda3 on /cdrom failed: Invalid argument
passwd: password expiry information changed.
dbus-daemon[751]: [session uid=999 pid=751] Activating service name='org.gtk.vfs.Daemon' requested by ':1.0' (uid=999 pid=752 comm="" label="unconfined")
dbus-daemon[751]: [session uid=999 pid=751] Successfully activated service 'org.gtk.vfs.Daemon'
dbus-daemon[751]: [session uid=999 pid=751] Activating service name='org.gtk.vfs.Metadata' requested by ':1.0' (uid=999 pid=752 comm="" label="unconfined")
fuse: device not found, try 'modprobe fuse' first
dbus-daemon[751]: [session uid=999 pid=751] Successfully activated service 'org.gtk.vfs.Metadata'
A connection to the bus can't be made
Using CD-ROM mount point /cdrom/
Identifying... [fa0560cb2d53c6cebfa16fec212250dd-2]
Scanning disc for index files...
Found 2 package indexes, 0 source indexes, 0 translation indexes and 1 signatures
Found label 'Ubuntu 21.04 _Hirsute Hippo_ - Alpha amd64 (20210216)'
This disc is called: 
'Ubuntu 21.04 _Hirsute Hippo_ - Alpha amd64 (20210216)'
Copying package lists...gpgv: Signature made Tue Feb 16 09:17:30 2021 UTC
gpgv:                using RSA key 843938DF228D22F7B3742BC0D94AA3F0EFE21092
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 21.04 _Hirsute Hippo_ - Alpha amd64 (20210216)]/ hirsute main restricted
Repeat this process for the rest of the CDs in your set.