After upgrading to Ubuntu 16.04 my system boot slow down consistently

To analyze the cause I used this command.

systemd-analyze plot > boot.xml
google-chrome ./boot.xml

I have found out NetworkManager-wait-online.service was taking 7s alone so I have disabled it.

systemctl mask NetworkManager-wait-online.service

Now the result of systemd-analyze plot show that my kernel boot time is the main cause:

Startup finished in 18.552s (kernel) + 4.704s (userspace) = 23.256s

The whole system use to boot in 10/15s no it take 18s only for the kernel

How can I found out the reason for 18s kernel boot time ?


I used @Nick suggestion dmesg > boot.txt and I was able to find out the bottleneck points

[    2.771745] clocksource: Switched to clocksource tsc
[    7.255226] EXT4-fs (dm-0): mounted filesystem with ordered data mode. Opts: (null)
[   18.512253] EXT4-fs (dm-1): mounted filesystem with ordered data mode. Opts: (null)

It looks there is some issue with the mounting part and maybe to LVM ...

Here my fstab:

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/mapper/ubuntu--vg-root /               ext4    errors=remount-ro       0       1
# /boot was on /dev/sda1 during installation
UUID=aa8cef14-44d2-43e4-be99-e2e826636e6b /boot           ext2    defaults  0       2

#/dev/mapper/ubuntu--vg-swap_1      none    swap        sw      0 0
/dev/mapper/cryptswap1  none        swap    sw          0 0
/dev/ubuntu-vg/usr      /usr        ext4    defaults    1 2
/dev/ubuntu-vg/opt      /opt        ext4    defaults    1 2
/dev/ubuntu-vg/home     /home       ext4    defaults    1 2
/dev/ubuntu-vg/web      /var/www/   ext4    defaults    1 2

/var/www/mysql         /var/lib/mysql/  none    bind 

Is this a bug ? Any solution/workaround ?

  • 2
    If you run dmesg > boot.txt immediately after booting your computer, you can examine the newly-created boot.txt to see the individual boot steps with their timestamps. Jun 11, 2016 at 3:13
  • thx see my update Jun 11, 2016 at 4:40
  • 1
    @Postadelmaga it will be great if you post answer and mark as solved :) Jun 11, 2016 at 4:45
  • 1
    @MohamedSlama I will when I find a solution Jun 12, 2016 at 6:53

1 Answer 1


With systemd do not separate anymore / and /usr

More informations here https://freedesktop.org/wiki/Software/systemd/separate-usr-is-broken/

  • should I remove .../usr line ? Oct 8, 2016 at 8:13
  • oh no ! do not touch /etc/fstab if you don't know what you do. Oct 10, 2016 at 9:13

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