====== Enable SSD Trim automatically ======
===== Continues TRIM =====
The real reason Ubuntu doesn’t TRIM SSDs by default is because the Linux kernel’s implementation of TRIM is slow and results in poor performance in normal use. Windows sends a TRIM command each time it deletes a file, telling the drive to immediately delete the bits of the file. Linux supports this when file systems are mounted with the “discard” option. However, Debian, Ubuntu — and other distributions — don’t do this by default for performance reasons. Continuous TRIM is not the most preferred way to issue TRIM commands in Linux. Continuous TRIM is enabled by the discard option for a mount in /etc/fstab: enables continuous TRIM in device operations:
<code>
/dev/sda1  /           ext4  defaults,discard   0  1
</code>
===== Periodic trim =====
Copy the available templates to the systemctl directory and enable and start them.
<code>
# cp /usr/lib/systemd/system/fstrim.{service,timer} /etc/systemd/system
# systemctl enable fstrim.timer
# systemctl start fstrim.timer
</code>
In case these templates are not available, see the contents below:
<code>
# cat fstrim.service

[Unit]
Description=Discard unused blocks on filesystems from /etc/fstab
Documentation=man:fstrim(8)

[Service]
Type=oneshot
ExecStart=/sbin/fstrim -Av
</code>
<code>
# cat fstrim.timer

[Unit]
Description=Discard unused blocks once a week
Documentation=man:fstrim

[Timer]
OnCalendar=weekly
AccuracySec=1h
Persistent=true

[Install]
WantedBy=timers.target
</code>
Check the status of the .timer with:
<code>
# systemctl list-timers
</code>
The output is quite useful:
<code>
EXT                         LEFT          LAST                         PASSED       UNIT                         ACTIVATES
Sun 2017-12-10 00:11:06 CET  6h left       Sat 2017-12-09 14:48:34 CET  2h 56min ago apt-daily.timer              apt-daily.service
Sun 2017-12-10 06:11:27 CET  12h left      Sat 2017-12-09 06:47:46 CET  10h ago      apt-daily-upgrade.timer      apt-daily-upgrade.servi
Sun 2017-12-10 16:28:34 CET  22h left      Sat 2017-12-09 16:28:34 CET  1h 16min ago systemd-tmpfiles-clean.timer systemd-tmpfiles-clean.
Mon 2017-12-11 00:00:00 CET  1 day 6h left n/a                          n/a          fstrim.timer                 fstrim.service

</code>