zram swap is not enabled after boot #6511

magicfoxt-magicfox · 2023-07-29T17:16:02Z

Required Information

DietPi version | G_DIETPI_VERSION_CORE=8 G_DIETPI_VERSION_SUB=19 G_DIETPI_VERSION_RC=1 G_GITBRANCH='master' G_GITOWNER='MichaIng' G_LIVE_PATCH_STATUS[0]='applied' G_LIVE_PATCH_STATUS[1]='applied' G_LIVE_PATCH_STATUS[2]='not applicable'
Distro version | bookworm 1
Kernel version | Linux DietPi0 6.1.21+ #1642 Mon Apr 3 17:19:14 BST 2023 armv6l GNU/Linux
SBC model | RPi Zero W (armv6l)
Power supply used | Raspberry Pi official power 2.5A
SD card used | Lexar HC I 16GB

Additional Information (if applicable)

Software title | dietpi-set_swapfile
Fresh bookworm install on PI0W
Can this issue be replicated on a fresh installation of DietPi? Yes
Bug report ID | 81d9818e-fe55-4f07-b9e6-be8e1493817c

Steps to reproduce

Enable zram swap auto-choice support in config /boot/dietpi.txt
First boot of DietPi

Expected behaviour

An enabled zram swap

Actual behaviour

zram swap is not enabled after each reboot

free
total used free shared buff/cache available
Mem: 488696 40260 373288 1640 87948 448436
Swap: 0 0 0

Extra details

journalctl -xe
...
Jul 29 18:08:53 DietPi0 systemd[1]: Started systemd-udevd.service - Rule-based Manager for Device Events and Files.
Subject: A start job for unit systemd-udevd.service has finished successfully
Defined-By: systemd
Support: https://www.debian.org/support

A start job for unit systemd-udevd.service has finished successfully.

The job identifier is 11.
Jul 29 18:08:54 DietPi0 kernel: zram0: detected capacity change from 0 to 487424
Jul 29 18:08:54 DietPi0 (udev-worker)[135]: zram0: Process 'chmod 0600 /dev/zram0' failed with exit code 1.
Jul 29 18:08:54 DietPi0 (udev-worker)[135]: zram0: Process '/sbin/swapon /dev/zram0' failed with exit code 255.
Jul 29 18:08:54 DietPi0 (udev-worker)[136]: zram0: /etc/udev/rules.d/98-dietpi-zram-swap.rules:1 Failed to write ATTR{/sys/devices/virtual/block/zram0/disksize}, ignoring: Device or resource busy
Jul 29 18:08:54 DietPi0 kernel: zram: Cannot change disksize for initialized device
Jul 29 18:08:54 DietPi0 (udev-worker)[136]: zram0: Process 'chmod 0600 /dev/zram0' failed with exit code 1.
Jul 29 18:08:55 DietPi0 (udev-worker)[136]: zram0: Process '/sbin/swapon /dev/zram0' failed with exit code 255.

Workaround

/boot/dietpi/func/dietpi-set_swapfile 1 zram

dietpi-set_swapfile
─────────────────────────────────────────────────────
Mode: Applying 1 zram

[ INFO ] DietPi-Set_swapfile | Disabling and deleting all existing swap files
[ OK ] DietPi-Set_swapfile | swapoff -a
removed '/etc/modules-load.d/dietpi-zram-swap.conf'
removed '/etc/udev/rules.d/98-dietpi-zram-swap.rules'
[ OK ] DietPi-Set_swapfile | Generating new swap space
[ INFO ] DietPi-Set_swapfile | Size = 238 MiB
[ INFO ] DietPi-Set_swapfile | Path = /dev/zram0
[ OK ] DietPi-Set_swapfile | eval echo 1 > /sys/block/zram0/reset
[ OK ] DietPi-Set_swapfile | eval echo '238M' > /sys/block/zram0/disksize
[ OK ] DietPi-Set_swapfile | chmod 0600 /dev/zram0
[ OK ] DietPi-Set_swapfile | mkswap /dev/zram0
[ OK ] DietPi-Set_swapfile | swapon /dev/zram0
[ OK ] DietPi-Set_swapfile | eval echo 'zram' > /etc/modules-load.d/dietpi-zram-swap.conf
[ OK ] DietPi-Set_swapfile | eval echo 'SUBSYSTEM=="block", KERNEL=="zram0", ACTION=="add", ATTR{disksize}="238M", RUN+="chmod 0600 /dev/zram0", RUN+="/sbin/mkswap /dev/zram0", RUN+="/sbin/swapon /dev/zram0"' > /etc/udev/rules.d/98-dietpi-zram-swap.rules
[ OK ] DietPi-Set_swapfile | eval echo 'swappiness=50' > /etc/sysctl.d/98-dietpi-zram-swap.conf
[ OK ] DietPi-Set_swapfile | Desired setting in /boot/dietpi.txt was already set: AUTO_SETUP_SWAPFILE_SIZE=238
[ OK ] DietPi-Set_swapfile | Desired setting in /boot/dietpi.txt was already set: AUTO_SETUP_SWAPFILE_LOCATION=zram
[ INFO ] DietPi-Set_swapfile | Setting /tmp tmpfs size: 357 MiB
[ OK ] DietPi-Set_swapfile | Desired setting in /etc/fstab was already set: tmpfs /tmp tmpfs size=357M,noatime,lazytime,nodev,nosuid,mode=1777
[ OK ] DietPi-Set_swapfile | systemctl daemon-reload
[ OK ] DietPi-Set_swapfile | mount -o remount /tmp

free
total used free shared buff/cache available
Mem: 488696 39508 373932 1640 88056 449188
Swap: 243708 0 243708

The text was updated successfully, but these errors were encountered:

magicfoxt-magicfox · 2023-07-30T11:38:55Z

Persitant workaround on reboot:

nano /etc/rc.local

#!/bin/sh
# Provisional workaround cf https://github.com/MichaIng/DietPi/issues/6511 #
/usr/sbin/modprobe zram && chmod 600 /dev/zram0 && /usr/sbin/mkswap /dev/zram0 && /usr/sbin/swapon /dev/zram0

chmod 755 /etc/rc.local

journalctl -u rc-local
Jul 30 13:25:11 DietPi0 systemd[1]: Starting rc-local.service - /etc/rc.local Compatibility...
Jul 30 13:25:11 DietPi0 rc.local[356]: mkswap: /dev/zram0: warning: wiping old swap signature.
Jul 30 13:25:11 DietPi0 rc.local[356]: Setting up swapspace version 1, size = 238 MiB (249556992 bytes)
Jul 30 13:25:11 DietPi0 rc.local[356]: no label, UUID=d5bf2ebd-9ca2-4256-84b8-3fdfac79ce2d
Jul 30 13:25:11 DietPi0 systemd[1]: Started rc-local.service - /etc/rc.local Compatibility.

MichaIng · 2023-07-30T12:15:06Z

Hmm, looks like the udev rule does not work in your case. Can you check the two files:

cat /etc/sysctl.d/98-dietpi-zram-swap.conf
cat /etc/udev/rules.d/98-dietpi-zram-swap.rules

The first is to enforce the kernel module to be loaded, hence this should make the modprobe zram in your rc.local obsolete. The second creates and enables the swap space, once the zram0 device is added/detected, same as the other commands in your rc.local do.

Little note on your workaround, until we have this fixed: You may want to add chmod 0600 /dev/zram0 as well, to ensure only root raw R/W access. By default, the disk group has R/W access as well, but this group is not meant to theoretically have full insights into any internal/private application data running on the server.

Is udev reporting any errors?

journalctl -u systemd-udevd

magicfoxt-magicfox · 2023-07-30T15:40:26Z

Hi MichaIng,

cat /etc/sysctl.d/98-dietpi-zram-swap.conf
swappiness=50

cat /etc/udev/rules.d/98-dietpi-zram-swap.rules
SUBSYSTEM=="block", KERNEL=="zram0", ACTION=="add", ATTR{disksize}="238M", RUN+="chmod 0600 /dev/zram0", RUN+="/sbin/mkswap /dev/zram0", RUN+="/sbin/swapon /dev/zram0"

You're right, errors are present on udev:

journalctl -u systemd-udevd
Jul 30 13:59:13 DietPi0 systemd[1]: Starting systemd-udevd.service - Rule-based Manager for Device Events and Files...
Jul 30 13:59:13 DietPi0 systemd-udevd[130]: Using default interface naming scheme 'v252'.
Jul 30 13:59:13 DietPi0 systemd[1]: Started systemd-udevd.service - Rule-based Manager for Device Events and Files.
Jul 30 13:59:14 DietPi0 (udev-worker)[135]: zram0: Process 'chmod 0600 /dev/zram0' failed with exit code 1.
Jul 30 13:59:14 DietPi0 (udev-worker)[135]: zram0: Process '/sbin/swapon /dev/zram0' failed with exit code 255.
Jul 30 13:59:14 DietPi0 (udev-worker)[136]: zram0: /etc/udev/rules.d/98-dietpi-zram-swap.rules:1 Failed to write ATTR{/sys/devices/virtual/block/zram0/disksize}, ignoring: Device or resource busy
Jul 30 13:59:14 DietPi0 (udev-worker)[136]: zram0: Process 'chmod 0600 /dev/zram0' failed with exit code 1.
Jul 30 13:59:15 DietPi0 (udev-worker)[136]: zram0: Process '/sbin/swapon /dev/zram0' failed with exit code 255.

Regards

magicfoxt-magicfox · 2023-07-30T15:56:43Z

In addition, I have errors too on a DietPi v8.19.1 PI3B (Debian 11.7) with zram swap enabled:

journalctl -u systemd-udevd
Jul 30 13:59:17 DietPi systemd[1]: Starting Rule-based Manager for Device Events and Files...
Jul 30 13:59:17 DietPi systemd-udevd[165]: Network interface NamePolicy= disabled on kernel command line, ignoring.
Jul 30 13:59:17 DietPi systemd[1]: Started Rule-based Manager for Device Events and Files.
Jul 30 13:59:17 DietPi systemd-udevd[168]: zram0: Process 'chmod 0600 /dev/zram0' failed with exit code 1.
Jul 30 13:59:18 DietPi systemd-udevd[171]: Using default interface naming scheme 'v247'.
Jul 30 13:59:18 DietPi systemd-udevd[175]: zram0: /etc/udev/rules.d/98-dietpi-zram-swap.rules:1 Failed to write ATTR{/sys/devices/virtual/block/zram0/disksize}, ignoring: Device or resource busy
Jul 30 13:59:18 DietPi systemd-udevd[175]: zram0: Process 'chmod 0600 /dev/zram0' failed with exit code 1.
Jul 30 13:59:18 DietPi systemd-udevd[175]: zram0: Process '/sbin/mkswap /dev/zram0' failed with exit code 1.
Jul 30 13:59:18 DietPi systemd-udevd[175]: zram0: Process '/sbin/swapon /dev/zram0' failed with exit code 255.

but zram swap is active:

free
               total        used        free      shared  buff/cache   available
Mem:          982532       60964      793044        3016      128524      902620
Swap:         490492           0      490492

MichaIng · 2023-07-30T16:51:35Z

Ah sorry, this is the first file I mean (wrong copy&paste):

cat /etc/modules-load.d/dietpi-zram-swap.conf

However, the issue can be seen in udev logs.

Process 'chmod 0600 /dev/zram0' failed with exit code 1.

The exit code 1 seems to be used for any error, so without the exact output, not sure what is wrong. But I guess the /dev node is not immediately present when /sys/class/block/zram0 is. Probably we simply need to wait for another second before setting it up.

The swapon command at least indeed returns 255 if the target does not exist:

root@VM-Bookworm:~# /sbin/swapon test; echo $?
swapon: cannot open test: No such file or directory
255

Hmm, that everything is executed twice makes me think that this is the problem: Two concurrent attempts to setup the swap space, breaking each other.

MichaIng · 2023-07-30T17:06:46Z

Bingo, assuring that it runs once only, by checking that the disk size is still zero, solves the double execution. But swapon still fails ...

Now I see the actual issue: systemd/systemd#23054

So here is how to solve the issue:

mkdir /etc/systemd/system/systemd-udevd.service.d
echo -e '[Service]\nSystemCallFilter=@swap' > /etc/systemd/system/systemd-udevd.service.d/dietpi-zram.conf

And the more cosmetic change to avoid the doubled execution:

echo 'SUBSYSTEM=="block", KERNEL=="zram0", ACTION=="add", ATTR{disksize}=="0", ATTR{disksize}="256M", RUN+="/bin/chmod 0600 /dev/zram0", RUN+="/sbin/mkswap /dev/zram0", RUN+="/sbin/swapon /dev/zram0"' > /etc/udev/rules.d/98-dietpi-zram-swap.rules

@magicfoxt-magicfox

- DietPi-Set_swapfile | Resolved an issue on Bookworm systems where zram swap space was not enabled automatically on boot due to missing syscall permissions. Many thanks to @magicfoxt-magicfox for reporting this issue: #6511

MichaIng · 2023-07-30T17:16:11Z

Fixed with: 55019bb

magicfoxt-magicfox · 2023-07-30T17:51:37Z

Thanks for your job ;)

Note the sysctl swappiness is not correcty set and later forced to 1 in /etc/sysctl.d/dietpi.conf, I propose this patch:

--- dietpi-set_swapfile.55019bb	2023-07-30 19:40:58.000000000 +0200
+++ dietpi-set_swapfile.55019bb.new	2023-07-30 19:45:16.000000000 +0200
@@ -112,7 +112,8 @@
 			# Make persistent, proceed with failure in case of R/O rootfs
 			G_EXEC_NOHALT=1 G_EXEC eval 'echo '\''zram'\'' > /etc/modules-load.d/dietpi-zram-swap.conf' || return 1
 			G_EXEC_NOHALT=1 G_EXEC eval "echo 'SUBSYSTEM==\"block\", KERNEL==\"zram0\", ACTION==\"add\", ATTR{disksize}==\"0\", ATTR{disksize}=\"${SWAP_SIZE}M\", RUN+=\"/bin/chmod 0600 /dev/zram0\", RUN+=\"/sbin/mkswap /dev/zram0\", RUN+=\"/sbin/swapon /dev/zram0\"' > /etc/udev/rules.d/98-dietpi-zram-swap.rules" || return 1
-			G_EXEC_NOHALT=1 G_EXEC eval 'echo '\''swappiness=50'\'' > /etc/sysctl.d/98-dietpi-zram-swap.conf' || return 1
+			G_EXEC_NOHALT=1 G_EXEC eval 'echo '\''vm.swappiness=50'\'' > /etc/sysctl.d/98-dietpi-zram-swap.conf' || return 1
+			G_EXEC_NOHALT=1 G_EXEC eval "sed -i 's/^vm.swap/\#vm.swap/' /etc/sysctl.d/dietpi.conf" || return 1
 			# Bookworm: Permit udev to run swapon: https://github.com/MichaIng/DietPi/issues/6511
 			G_EXEC_NOHALT=1 G_EXEC mkdir -p /etc/systemd/system/systemd-udevd.service.d
 			G_EXEC_NOHALT=1 G_EXEC eval 'echo -e '\''[Service]\nSystemCallFilter=@swap'\'' > /etc/systemd/system/systemd-udevd.service.d/dietpi-zram.conf'

MichaIng · 2023-07-30T18:00:46Z

You are right about the swappiness 😮. We create a config to set it to 50, but it is alphanumerically ordered before the default config file, so is overridden with the default 1.

This file needs to be renamed to 97-dietpi.conf, so 98-dietpi-zram-swap.conf is applied afterwards and 99-sysctl.conf (which is a symlink to /etc/sysctl.conf) is applied last, i.e. overrides everything else.

However, a swappiness of 1 is not "false", but it makes sense to make more/earlier use of a zram swap compared to a disk swap file.

EDIT: I should have read more carefully. Indeed the vm. is missing as well.

MichaIng added the Investigating 🤔 label Jul 30, 2023

MichaIng added the Upstream change label Jul 30, 2023

MichaIng added this to the v8.21 milestone Jul 30, 2023

MichaIng added Solution available 🥂 Definite solution has been done and removed Investigating 🤔 labels Jul 30, 2023

This was referenced Aug 20, 2023

Beta v8.21.0 #6563

Merged

Open Beta v8.21 | Please help testing and hardening our upcoming release #6564

Closed

Release v8.21 #6580

Merged

MichaIng closed this as completed Aug 26, 2023

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zram swap is not enabled after boot #6511

zram swap is not enabled after boot #6511

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zram swap is not enabled after boot #6511

zram swap is not enabled after boot #6511

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magicfoxt-magicfox commented Jul 29, 2023 • edited by MichaIng Loading

Required Information

Additional Information (if applicable)

Steps to reproduce

Expected behaviour

Actual behaviour

Extra details

Workaround

magicfoxt-magicfox commented Jul 30, 2023 • edited Loading

Persitant workaround on reboot:

MichaIng commented Jul 30, 2023

magicfoxt-magicfox commented Jul 30, 2023

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