Essential and strongly recommended things to do directly after a Kubuntu 24.04 LTS installation

[lednyk]

Very helpful, thank you!
Actually in my '/etc/fstab' the root directory (I have not a separate '/home') was configured with the option 'discard'.
I hope the developers will fix this bug in 24.04.1 LTS.

[claydoh]

wonder why some installs have the discard option set still, and zero of mine have it except for the one I did during pre-release testing, which was fixed before the final release.
I did one yesterday, even.

[jlittle]

I think discard is the default. On my 24.04 the fstab doesn't have any discard options, and mount says both SATA and NVMe SSDs have been mounted with discard=async.

[lednyk]

jlittle

In my Kubuntu 24.04 (installed from scratch) the fstab does have a 'discard' option.
# systemctl status fstrim.timer

fstrim.timer - Discard unused filesystem blocks once a week
Loaded: loaded (/usr/lib/systemd/system/fstrim.timer; enabled; preset: enabled)
Active: active (waiting) since Thu 2024-08-15 15:16:39 CEST; 16min ago
Trigger: Mon 2024-08-19 00:28:06 CEST; 3 days left
Triggers: fstrim.service
Docs: man:fstrim

ago 15 15:16:39 kubuntu systemd[1]: Started fstrim.timer
Discard unused filesystem blocks once a week.

If Kubuntu 24.04 discards unused filesystem blocks once a week (with fstrim.timer), why should be present the option 'discard' in '/etc/fstab'?

[lednyk]

I found this post:
Automatic TRIM (Deprecated, Slow)

Automatic TRIM has been supported since Ubuntu 10.10 (kernel 2.6.33) with the EXT4 file system. However, sending TRIM commands to the SSD in real-time - after every delete - has been recognized to make deletion much slower than usual on some drives. Therefore a weekly scheduled TRIM via a cron job (described above) is recommended.

To enable automatic TRIM on a drive or partition, they need to be mounted with the discard option in fstab. Firstly backup your fstab then open it for editing:
sudo cp /etc/fstab ~/fstab-backup
gksudo gedit /etc/fstab

Add 'discard' to the fstab options entry (comma separated) for the SSD drive or each partition:
UUID=00000000-0000-0000-0000-000000000000 / ext4 discard 0 1

If Automatic TRIM is deprecated, why my Kubuntu 24.04 (installed from scratch) enables 'discard' option in fstab?

[Virginio Miranda]

Mine 24.04 installed from scratch enabled discard option in fstab too.

What the OP said in his post was:

replace the "discard" option with "defaults", because a systemd timer for fstrim is already running

so, i checked this, and it is really true:

systemctl status fstrim.timer
● fstrim.timer - Discard unused filesystem blocks once a week
Loaded: loaded (/usr/lib/systemd/system/fstrim.timer; enabled; preset: enabled)
Active: active (waiting) since Sat 2024-08-10 01:31:50 -03; 5 days ago
Trigger: Mon 2024-08-19 00:22:47 -03; 3 days left
Triggers: ● fstrim.service
Docs: man:fstrim

system systemd[1]: Started fstrim.timer - Discard unused filesystem blocks once a week.

So, both are running: fstrim.timer and discard. I need to replace my fstab, but the question is why 24.04 still use discard option? Still a bug ?

[claydoh]

I think discard is the default. On my 24.04 the fstab doesn't have any discard options, and mount says both SATA and NVMe SSDs have been mounted with discard=async.

https://www.phoronix.com/news/Btrfs-...iscard-Default

Unrelated to the discard option for mounting, as well as ext4, I think.

[claydoh]

So, both are running: fstrim.timer and discard. I need to replace my fstab, but the question is why 24.04 still use discard option? Still a bug ?

It must be. My install, zero of them, have discard set in the /etc/fstab
My guess is zero people have reported it since release?
Kubuntu's Calamares setup did have this as part of its default fstab setting while in pre-release, but this was removed before the final release.

But, how are you determining that you have the discard mount option being used? Nothing you show actually indicates this at all.

Note the mount option called discard is not the same thing as the description used for the fstrim.timer systemd service.

My freshly installed Noble does not have it in the fstab:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a device; this may
# be used with UUID= as a more robust way to name devices that works even if
# disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
UUID=5BE0-1D23 /boot/efi vfat defaults 0 2
UUID=b0b23e67-a876-4250-ab86-eeba890613b6 / ext4 defaults 0 1
/swapfile swap swap defaults 0 0

Nor is discard used as a defualt mount option by *buntu.

$ mount | grep sda
/dev/sda2 on / type ext4 (rw,relatime)
/dev/sda1 on /boot/efi type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,io charset=iso8859-1,shortname=mixed,errors=remount-ro)

​

fstrim.timer is a system action run at an interval (sort of like a cron job), not something built in to the file system or kernel.

In my Kubuntu 24.04 (installed from scratch) the fstab does have a 'discard' option.
# systemctl status fstrim.timer

fstrim =/= discard
The terminal output you show does not show discard being physically included in the fstab file which was the original pre-release bug.

I really really do think that Schwarzer Kater might look at removing this suggestion since in my strong opinion, it is not valid, since the fstab no longer has the 'discard' text erroneously included in the text file.

[Virginio Miranda]

But, how are you determining that you have the discard mount option being used? Nothing you show actually indicates this at all.

UUID=47fd72de-ef9a-4f97-bc94-cf7c8387d238 / ext4 discard 0 1
/swapfile swap swap defaults 0 0
tmpfs /tmp tmpfs noatime,mode=1777,size=8G 0 0
UUID=8c158569-882b-4039-9199-9c9a00e34c62 /media/LVM ext4 defaults 0 0
UUID=db8fc645-13b9-49c7-92f6-2efb18d47344 /media/virginio/Linux\0401TB\040A ext4 defaults 0 0
UUID=39e38ed5-aa6a-40ce-9bbd-79425f496a91 /media/virginio/Linux\0401TB\040B ext4 defaults 0 0
UUID=DCBAD118BAD0F04E /media/virginio/Seagate\040Expansion\040Drive ntfs defaults 0 0

And my install is not a pre release. It is a official release.

mount | grep sdh
/dev/sdh1 on / type ext4 (rw,relatime,discard)
/dev/sdh1 on /var/snap/firefox/common/host-hunspell type ext4 (ro,noexec,noatime,discard)


systemctl status fstrim.timer
● fstrim.timer - Discard unused filesystem blocks once a week
Loaded: loaded (/usr/lib/systemd/system/fstrim.timer; enabled; preset: enabled)
Active: active (waiting) since Sat 2024-08-10 01:31:50 -03; 5 days ago
Trigger: Mon 2024-08-19 00:22:47 -03; 3 days left
Triggers: ● fstrim.service
Docs: man:fstrim

system systemd[1]: Started fstrim.timer - Discard unused filesystem blocks once a week.

So, fstrim.timer is enabled by default running once a week and fstab has discard by default.

[jglen490]

I downloaded my 24.04 ISO shortly after its release announcement. It came directly from the Kubuntu page, and this is the fstab:

cat fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a device; this may
# be used with UUID= as a more robust way to name devices that works even if
# disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
UUID=D912-B405 /boot/efi vfat defaults 0 2
UUID=ac5a72f4-8003-4890-8f0e-6176ee726d12 / ext4 defaults 0 1
UUID=870436af-1189-421f-8240-e35613dba718 /home ext4 defaults 0 2
UUID=93e084bc-dac6-4d6e-bb72-608fbdb1ed53 swap swap defaults 0 0
# /swapfile swap swap defaults 0 0
tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0

I didn't make any changes after install.

[lednyk]

Kubuntu 24.04.1 LTS (re-installed from scratch in a UEFI pc): I have again the option 'discard' in '/etc/fstab' and I replaced it by hand with 'defaults'.

[...]
A popular method used in the past, not recommended today, was to enable automatic TRIM by adding the discard option in the /etc/fstab file.

Although apparently effective, this method is not convenient or even disadvantageous because:

• Forces the system to run TRIM continuously and with the system booted, after every single file deletion (in most cases it is sufficient to run it once a week or a day).
• For the previous reason, it can cause significant resource usage, with frequent system slowdowns.
• In recent versions of Ubuntu, the command is already run automatically handled by systemd.

[...]

Check if 'discard' is enabled with the command:

cat /etc/fstab

Source here.

[jlittle]

I'm confused about this.

My /etc/fstab does not mention discard, but findmnt --real shows discard=async for both mounted SSDs, an NVMe and a SATA SSD. Various forum posts say discard=async became the default for btrfs from Linux kernel 6.2.

So the default is discard=async; do you think we should explicitly add nodiscard?

[claydoh]

So the default is discard=async; do you think we should explicitly add nodiscard?

Why? This is what the filesystem and kernel devs seem to want.
It might be useful to disable the fstrim timer, but that wouldn't actually harm anything, I'd think.

https://btrfs.readthedocs.io/en/latest/Trim.html
https://man.archlinux.org/man/fstrim.8.en
https://www.reddit.com/r/btrfs/comme..._fstrim_since/

[Cincinnatus]

Accident

[Cincinnatus]

Is your SSD always attached and mounted at boot? Or is it only attached to an already booted system when you feel the need for some Linux?

It's always attached. I have Window installed on PC but for some reason couldn't install Linux on it so I had to use an enclosure instead. Bottom line is I try to not even use Windows, but every now and then Linux doesn't want to boot until I update Windows first so I still have to get into Windows sometimes