Linux auto-mounting USB with UDev

Question

My task is to have a custom mount point and for the mount itself to happen automatically. that is, the device is connected, a folder with its name is created in some place (/mnt/usb/{name}) and the data is mounted there. when the device is disconnected, the folder is unmounted and deleted

Wrote a udev rule

ACTION=="add", SUBSYSTEM=="block", KERNEL=="sd[b-z][0-9]", ENV{ID_BUS}=="usb", \
ENV{ID_TYPE}=="disk", ENV{ID_FS_USAGE}=="filesystem", \
RUN+="/bin/mount -w -o umask=0000,uid=0,gid=0 /dev/%k /mnt/usb_drives"

ACTION=="remove", SUBSYSTEM=="block", KERNEL=="sd[b-z][0-9]", ENV{ID_BUS}=="usb", \
ENV{ID_TYPE}=="disk", ENV{ID_FS_USAGE}=="filesystem", RUN+="/bin/umount /mnt/usb_drives"

I look at df -h and I don't see my mounted device there, I tried writing a rule via pmount and still no result. Nothing is written in the logs, or it gives an error with a return value of 1

I tried to write commands in scripts, but as I understand it, the problem is that HE DOESN'T WANT TO RUN THROUGH THE ROOT USER. HOW IS THIS??

SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", \
ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", \
ENV{UDISKS_AUTO}="0"

ACTION=="add", SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", \
ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", \
RUN+="sh /etc/udev/rules.d/mount-usb.sh %k"
#!/usr/bin/sudo bash
sleep 5

NAME_DEV=$1
mkdir "/mnt/usb/$NAME_DEV"
sudo /bin/mount "/dev/$NAME_DEV" "/mnt/usb/$NAME_DEV"

The device folder is created but the data is not mounted in it

EDIT

Changed the rule and the script, and also moved the script to /usr/bin/

/usr/bin/mount-usb.sh

#!/usr/bin/sudo bash
NAME_DEV=$1
/usr/bin/pmount --umask=000 -s -w "/dev/$NAME_DEV"

/etc/udev/rules.d/99-usb-mount.rules

SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", ENV{UDISKS_AUTO}="0"

ACTION=="add", SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", RUN+="/usr/bin/mount-usb.sh %k"

After connecting a USB flash drive, a folder is created in /media, but data is still not mounted in it

NEW EDIT

SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", \
ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", \
ENV{UDISKS_AUTO}="0"

ACTION=="add", SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", \
ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", \
RUN+="mkdir /mnt/usb/%k && systemd-mount --no-block -o umask=000,rw /dev/%k /mnt/usb/%k"

Returns an error as if it were access rights...

systemd-udevd[3099]: sdb1: Process 'mkdir /mnt/usb/sdb1 && systemd-mount --no-block -o umask=000,rw /dev/sdb1 /mnt/usb/sdb1' failed with exit code 1.

TRYING WITH SCRIPT

/usr/bin/mount-usb.sh

#!/usr/bin/sudo bash

NAME_DEV=$1
MOUNT_POINT="/mnt/usb/${NAME_DEV}"

mkdir "${MOUNT_POINT}"

/usr/bin/mount -o umask=000,rw "/dev/${NAME_DEV}" "${MOUNT_POINT}"

/etc/udev/rules.d/99-usb-mount.rules

SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", \
ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", \
ENV{UDISKS_AUTO}="0"

ACTION=="add", SUBSYSTEM=="block", KERNEL=="sd[a-z][0-9]", \
ENV{ID_BUS}=="usb", ENV{ID_TYPE}=="disk", \
RUN+="/usr/bin/mount-usb.sh %k"

The script runs, but the device still doesn't mount in the folder I create. the folder I mount in (/mnt/usb) is set to chmod 777.

Folder /mnt/usb/sdb1 was created, but there is no data from the usb device in it

richstog-VirtualBox sudo[4342]:     root : TTY=unknown ; PWD=/ ; USER=root ; COMMAND=/usr/bin/bash /usr/bin/mount-usb.sh sdb1

Answer 1

Systemd-udev doesn't support directly mounting filesystems from within udev rules. It's not a matter of user privileges – udev isolates the RUN subprocess in a new namespace, so that any mounts it creates are only visible to itself and will disappear when the process exits. This is done deliberately, from what I remember.

Either call systemd-mount --no-block instead (which mounts things indirectly, by sending off a request to systemd) if you have a recent enough version of systemd, or define a static /etc/fstab entry and invoke it through ENV{SYSTEMD_WANTS} or through systemctl --no-block start. Each fstab entry generates a .mount unit like media-foo.mount; systemd-mount will generate those dynamically.

(In both cases the --no-block is needed because systemd only considers the device "active" after its rules have finished.)

The other approach is to avoid RUN completely, but instead to have some daemon waiting and reacting to the final "rules complete" event that udev emits after it's done with all .rules for /dev/sdx. Systemd itself can do this, through the aforementioned ENV{SYSTEMD_WANTS}. But other programs can as well – that's how removable media gets automounted in graphical desktop environments like GNOME or KDE: your desktop listens for udev events.

Graphical environments usually have udisks2, which mounts things under /run/media/$USER (though there's an udev ENV that can move it back to /media). Udisks2 still does nothing on its own but needs to be triggered by something like udiskie if you don't already have a "full" that would do so. (And no, not by udev RUN; it doesn't "see" disks until after udev rules are done.)

(There are certainly also some "lightweight" options if udiskie is too much, but I can't remember any offhand.)