Remounting root file system takes a lot of time

Asked by Ravi Kumar on 2018-11-21

I have slow boot. From systemd-analyze blame, i can see that dev.sda1(which holds root file system) is taking a lot of time(around 9 seconds)
Now,I have 4 ext4 partitions in my system.

From dmesg :
<pre>1. EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts: (null)--> Here root file system is mounted in read only mode for fsck
2. EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro --> Here root file system is remounted in read-write mode
3. EXT4-fs (sda7): mounted filesystem with ordered data mode. Opts: (null) --> Here sda7 is mounted on /home
4. EXT4-fs (sda5): mounted filesystem with ordered data mode. Opts: (null) --> Here sd5 is mounted on /mnt/data</pre>

My /etc/fstab look like this:

<pre># <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/sda1 during installation
UUID=e27bebbb-f8e8-4bd7-9849-2421323efc3a / ext4 errors=remount-ro 0 1
# /home was on /dev/sda7 during installation
UUID=0622bb8c-dd7d-4035-8c92-b0f729a60035 /home ext4 defaults 0 2
# swap was on /dev/sda6 during installation
UUID=dc788cde-d82a-4bdc-a5b1-8def34546012 none swap sw 0 0
# /dev/sda5 was mounted on /mnt/data post installation
UUID=144ba46c-e53d-4e0f-9da2-5a3d31bb617a /mnt/data ext4 defaults 0 2</pre>

My question is why remounting root file system in read write mode takes so much time(around 9 sec).

Question information

English Edit question
Ubuntu util-linux Edit question
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Last reply:
Lin Rongxiang (linrx) said : #1

Can you try this perhaps and let us know what is displayed.

systemd-analyze blame

Ravi Kumar (ravik0198) said : #2

As i mentioned in the start of question, systemd-analyze blame pinpoints to dev.sda1 as major culprit and it takes around 9-10 seconds.

Ravi Kumar (ravik0198) said : #3

systemd-analayze blame output:

10.484s systemd-journal-flush.service
          9.669s dev-sda1.device
          8.385s keyboard-setup.service
          6.817s systemd-tmpfiles-setup-dev.service
          6.510s systemd-sysctl.service
          2.943s systemd-fsck@dev-disk-by\x2duuid-0622bb8c\x2ddd7d\x2d4035\x2d8c92\x2db0f729a60035.service
          2.785s thermald.service
          2.601s NetworkManager.service
          2.410s ModemManager.service
          2.253s udisks2.service
          2.157s accounts-daemon.service
          1.938s systemd-random-seed.service
          1.917s snapd.service
          1.914s plymouth-start.service
          1.761s networkd-dispatcher.service
          1.679s mnt-data.mount
          1.176s tlp.service
          1.152s polkit.service
           795ms grub-common.service
           699ms systemd-fsck@dev-disk-by\x2duuid-144ba46c\x2de53d\x2d4e0f\x2d9da2\x2d5a3d31bb617a.service
           673ms systemd-modules-load.service
           612ms dev-mqueue.mount
           611ms sys-kernel-debug.mount
           609ms dev-hugepages.mount
           483ms NetworkManager-wait-online.servic

I suggest you boot to Ubuntu live CD / USB desktop and run a full fsck on the file system (while it is unmounted)

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