Silencing boot messages
You should be able to achieve this with the kernel parameter loglevel=
or quiet
loglevel= All Kernel Messages with a loglevel smaller than the
console loglevel will be printed to the console. It can
also be changed with klogd or other programs. The
loglevels are defined as follows:
0 (KERN_EMERG) system is unusable
1 (KERN_ALERT) action must be taken immediately
2 (KERN_CRIT) critical conditions
3 (KERN_ERR) error conditions
4 (KERN_WARNING) warning conditions
5 (KERN_NOTICE) normal but significant condition
6 (KERN_INFO) informational
7 (KERN_DEBUG) debug-level messages
quiet [KNL] Disable most log messages
I am not sure at exactly what level this would be hidden (or how quiet you would like your boot to be).
Temporarily
reboot your computer, and at the grub menu hit e
to edit the boot parameters.
scroll down to the end of the linux...
line using the arrow keys
add desired loglevel
parameter or quiet
to the end of that line. example:
linux /vmlinuz-4.4.0-21.generic.efi.signed root=/dev/mapper/encrypted ro loglevel=4
or
linux /vmlinuz-4.4.0-21.generic.efi.signed root=/dev/mapper/encrypted ro quiet
when done editing, proceed to boot by pressing F10
Persistently
To do this, edit /etc/default/grub
edit the line:
GRUB_CMDLINE_LINUX_DEFAULT=
uncomment it if needed, and add the desired log level or quiet -- for example GRUB_CMDLINE_LINUX_DEFAULT="loglevel=4"
or GRUB_CMDLINE_LINUX_DEFAULT="quiet"
and run sudo update-grub
fsck messages
remove fsck from initramfs
fsck is run by default by the initramfs. by removing it and having systemd run fsck we will be able to redirect the output.
see man initramfs
and wiki.ubuntu.com/Initramfs for more info on removing fsck from the ramfs.
systemd fsck
From the arch wiki:
Now copy the files systemd-fsck-root.service and systemd-fsck@.service located at /usr/lib/systemd/system/ to /etc/systemd/system/ and edit them, configuring StandardOutput and StandardError like this:
[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/usr/lib/systemd/systemd-fsck
StandardOutput=null
StandardError=journal+console
TimeoutSec=0
In Ubuntu, these files are both located in /lib/systemd/system
If the file system is not checked by the initramfs during boot, systemd-fsck-root.service will automatically be run.
see http://manpages.ubuntu.com/manpages/wily/man8/systemd-fsck@.service.8.html