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mbw

Member

Registered: 2020-01-04

Posts: 38

[Solved] Mounting LUKS-encrypted partition with uid,guid mount options

Hello,

I have a backup drive containing one single LUKS-encrypted partition, which in turn contains an ext4 filesystem.
Just to be overly explicit, it was created like this

wipefs -a /dev/sda
parted
    p
    rm 1 2  # Print and remove previous partitions.
    mktable gpt
    mkpart primary ext4
^D

cryptsetup luksFormat /dev/sda
cryptsetup open /dev/sda1 backup-disk
mkfs.ext4 /dev/mapper/backup-disk.
cryptsetup close backup-disk

Thus, as a normal user,  I can mount my backup partition via

sudo cryptsetup open /dev/sda1 backup-disk
sudo mount /dev/mapper/backup/disk /mnt/backup

This backup partition contains some data that was backed up as root. Among this data are audio/video files I would like to play via mpv.
Unfortunately, the pipewire service is not available for the root user. For this reason, I would like to mount via

sudo cryptsetup open /dev/sda1 backup-disk
sudo mount -o uid=1000,gid=1000 /dev/mapper/backup/disk /mnt/backup

to have these files show up as belonging to my own user.

This however does not work:

$ sudo cryptsetup open /dev/sda1 backup-disk && sudo mount -o uid=1000,gid=1000 /dev/mapper/backup-disk /mnt/backup/
[sudo] password for mbw:
Enter passphrase for /dev/sda1:
mount: /mnt/backup: wrong fs type, bad option, bad superblock on /dev/mapper/backup-disk, missing codepage or helper program, or other error.
       dmesg(1) may have more information after failed mount system call.

$ sudo dmesg
...
[195380.982734] nvidia-modeset: WARNING: GPU:0: BOE Technology Group Co., Ltd (DP-4): G-SYNC Compatible: EDID min refresh rate invalid, disabling G-SYNC Compatible.
[195476.790603] usb 2-3: new SuperSpeed USB device number 10 using xhci_hcd
[195476.806913] usb 2-3: New USB device found, idVendor=04e8, idProduct=61fb, bcdDevice= 1.00
[195476.806928] usb 2-3: New USB device strings: Mfr=2, Product=3, SerialNumber=1
[195476.806934] usb 2-3: Product: PSSD T7 Shield
[195476.806939] usb 2-3: Manufacturer: Samsung
[195476.806944] usb 2-3: SerialNumber: S76ZNJ0W307130H
[195476.811822] scsi host5: uas
[195476.812783] scsi 5:0:0:0: Direct-Access     Samsung  PSSD T7 Shield   0    PQ: 0 ANSI: 6
[195476.814671] sd 5:0:0:0: [sda] 7814037168 512-byte logical blocks: (4.00 TB/3.64 TiB)
[195476.814805] sd 5:0:0:0: [sda] Write Protect is off
[195476.814811] sd 5:0:0:0: [sda] Mode Sense: 43 00 00 00
[195476.814979] sd 5:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[195476.815152] sd 5:0:0:0: [sda] Preferred minimum I/O size 512 bytes
[195476.815157] sd 5:0:0:0: [sda] Optimal transfer size 33553920 bytes
[195477.371833]  sda: sda1
[195477.372210] sd 5:0:0:0: [sda] Attached SCSI disk
[195482.015978] nvidia-modeset: WARNING: GPU:0: BOE Technology Group Co., Ltd (DP-4): G-SYNC Compatible: EDID min refresh rate invalid, disabling G-SYNC Compatible.
[195515.660619] dm-0: detected capacity change from 7813901887 to 0

$ sudo journalctl -S today
...
Jul 24 14:51:04 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:04 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2964968, code=1
Jul 24 14:51:04 legion kernel: usb 2-3: new SuperSpeed USB device number 10 using xhci_hcd
Jul 24 14:51:04 legion kernel: usb 2-3: New USB device found, idVendor=04e8, idProduct=61fb, bcdDevice= 1.00
Jul 24 14:51:04 legion kernel: usb 2-3: New USB device strings: Mfr=2, Product=3, SerialNumber=1
Jul 24 14:51:04 legion kernel: usb 2-3: Product: PSSD T7 Shield
Jul 24 14:51:04 legion kernel: usb 2-3: Manufacturer: Samsung
Jul 24 14:51:04 legion kernel: usb 2-3: SerialNumber: S76ZNJ0W307130H
Jul 24 14:51:04 legion kernel: scsi host5: uas
Jul 24 14:51:04 legion kernel: scsi 5:0:0:0: Direct-Access     Samsung  PSSD T7 Shield   0    PQ: 0 ANSI: 6
Jul 24 14:51:04 legion kernel: sd 5:0:0:0: [sda] 7814037168 512-byte logical blocks: (4.00 TB/3.64 TiB)
Jul 24 14:51:04 legion kernel: sd 5:0:0:0: [sda] Write Protect is off
Jul 24 14:51:04 legion kernel: sd 5:0:0:0: [sda] Mode Sense: 43 00 00 00
Jul 24 14:51:04 legion kernel: sd 5:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
Jul 24 14:51:04 legion kernel: sd 5:0:0:0: [sda] Preferred minimum I/O size 512 bytes
Jul 24 14:51:04 legion kernel: sd 5:0:0:0: [sda] Optimal transfer size 33553920 bytes
Jul 24 14:51:04 legion mtp-probe[2964976]: checking bus 2, device 10: "/sys/devices/pci0000:00/0000:00:14.0/usb2/2-3"
Jul 24 14:51:04 legion mtp-probe[2964976]: bus: 2, device: 10 was not an MTP device
Jul 24 14:51:04 legion mtp-probe[2964989]: checking bus 2, device 10: "/sys/devices/pci0000:00/0000:00:14.0/usb2/2-3"
Jul 24 14:51:04 legion mtp-probe[2964989]: bus: 2, device: 10 was not an MTP device
Jul 24 14:51:05 legion kernel:  sda: sda1
Jul 24 14:51:05 legion kernel: sd 5:0:0:0: [sda] Attached SCSI disk
Jul 24 14:51:08 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:08 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:08 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:08 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965031, code=1
Jul 24 14:51:10 legion kernel: nvidia-modeset: WARNING: GPU:0: BOE Technology Group Co., Ltd (DP-4): G-SYNC Compatible: EDID min refresh rate invalid, disabling G-SYNC Compatible.
Jul 24 14:51:11 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:11 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:11 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:11 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965065, code=1
Jul 24 14:51:13 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:13 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:13 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:13 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965104, code=1
Jul 24 14:51:16 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:16 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:16 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:16 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965142, code=1
Jul 24 14:51:17 legion dbus-daemon[498]: [system] Activating via systemd: service name='org.freedesktop.home1' unit='dbus-org.freedesktop.home1.service' requested by ':1.2610' (uid=0 pid=2965>
Jul 24 14:51:17 legion dbus-daemon[498]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.home1.service': Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:51:17 legion sudo[2965153]: pam_systemd_home(sudo:auth): systemd-homed is not available: Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:51:20 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:20 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:20 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:20 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965187, code=1
Jul 24 14:51:22 legion sudo[2965153]:      mbw : TTY=pts/1 ; PWD=/home/mbw ; USER=root ; COMMAND=/usr/bin/cryptsetup open /dev/sda1 backup-disk
Jul 24 14:51:22 legion sudo[2965153]: pam_unix(sudo:session): session opened for user root(uid=0) by mbw(uid=1000)
Jul 24 14:51:23 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:23 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:23 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:23 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965223, code=1
Jul 24 14:51:25 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:25 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:25 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:25 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965258, code=1
Jul 24 14:51:27 legion sudo[2965153]: pam_unix(sudo:session): session closed for user root
Jul 24 14:51:27 legion systemd[827]: Started Fetch Emails.
Jul 24 14:51:27 legion dbus-daemon[498]: [system] Activating via systemd: service name='org.freedesktop.home1' unit='dbus-org.freedesktop.home1.service' requested by ':1.2611' (uid=0 pid=2965>
Jul 24 14:51:27 legion dbus-daemon[498]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.home1.service': Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:51:27 legion sudo[2965382]: pam_systemd_home(sudo:account): systemd-homed is not available: Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:51:27 legion sudo[2965382]:      mbw : TTY=pts/1 ; PWD=/home/mbw ; USER=root ; COMMAND=/usr/bin/mount -o uid=1000,gid=1000 /dev/mapper/backup-disk /mnt/backup/
Jul 24 14:51:27 legion sudo[2965382]: pam_unix(sudo:session): session opened for user root(uid=0) by mbw(uid=1000)
Jul 24 14:51:27 legion sudo[2965382]: pam_unix(sudo:session): session closed for user root
Jul 24 14:51:29 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:29 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:29 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:29 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965433, code=1
Jul 24 14:51:41 legion systemd[827]: sync-mail.service: Consumed 1.999s CPU time.
Jul 24 14:51:41 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:41 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:41 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:41 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965563, code=1
Jul 24 14:51:43 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:43 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:43 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:43 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965591, code=1
Jul 24 14:51:43 legion dbus-daemon[498]: [system] Activating via systemd: service name='org.freedesktop.home1' unit='dbus-org.freedesktop.home1.service' requested by ':1.2612' (uid=0 pid=2965>
Jul 24 14:51:43 legion dbus-daemon[498]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.home1.service': Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:51:43 legion sudo[2965592]: pam_systemd_home(sudo:account): systemd-homed is not available: Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:51:43 legion sudo[2965592]:      mbw : TTY=pts/1 ; PWD=/home/mbw ; USER=root ; COMMAND=/usr/bin/cryptsetup close backup-disk
Jul 24 14:51:43 legion sudo[2965592]: pam_unix(sudo:session): session opened for user root(uid=0) by mbw(uid=1000)
Jul 24 14:51:43 legion kernel: dm-0: detected capacity change from 7813901887 to 0
Jul 24 14:51:43 legion sudo[2965592]: pam_unix(sudo:session): session closed for user root
Jul 24 14:51:46 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:46 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:46 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:46 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965633, code=1
Jul 24 14:51:49 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:49 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:49 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:49 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965666, code=1
Jul 24 14:51:53 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:53 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:53 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:53 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965710, code=1
Jul 24 14:51:55 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:55 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:55 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:55 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965733, code=1
Jul 24 14:51:58 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:51:58 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:51:58 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:51:58 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965767, code=1
Jul 24 14:52:02 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:02 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:02 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:02 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965810, code=1
Jul 24 14:52:04 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:04 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:04 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:04 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965833, code=1
Jul 24 14:52:07 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:07 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:07 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:07 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:07 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:07 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:07 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965866, code=1
Jul 24 14:52:10 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:10 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:10 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:10 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965900, code=1
Jul 24 14:52:13 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:13 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:13 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:13 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965932, code=1
Jul 24 14:52:15 legion dbus-daemon[498]: [system] Activating via systemd: service name='org.freedesktop.home1' unit='dbus-org.freedesktop.home1.service' requested by ':1.2613' (uid=0 pid=2965>
Jul 24 14:52:15 legion dbus-daemon[498]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.home1.service': Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:52:15 legion sudo[2965945]: pam_systemd_home(sudo:account): systemd-homed is not available: Unit dbus-org.freedesktop.home1.service not found.
Jul 24 14:52:15 legion sudo[2965945]:      mbw : TTY=pts/1 ; PWD=/home/mbw ; USER=root ; COMMAND=/usr/bin/journalctl -S 2023-07-24T14:50:00
Jul 24 14:52:15 legion sudo[2965945]: pam_unix(sudo:session): session opened for user root(uid=0) by mbw(uid=1000)
Jul 24 14:52:15 legion sudo[2965945]: pam_unix(sudo:session): session closed for user root
Jul 24 14:52:16 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:16 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:16 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:16 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2965970, code=1
Jul 24 14:52:19 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:19 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:19 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:19 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2966003, code=1
Jul 24 14:52:25 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:25 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:25 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:25 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2966059, code=1
Jul 24 14:52:28 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:28 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:28 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:28 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2966092, code=1
Jul 24 14:52:32 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:32 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:32 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:32 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2966136, code=1
Jul 24 14:52:35 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:35 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:35 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:35 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2966171, code=1
Jul 24 14:52:38 legion dhcpcd[508]: dhcp6_openudp: Address already in use
Jul 24 14:52:38 legion dhcpcd[508]: ps_inet_listenin6: Address already in use
Jul 24 14:52:38 legion dhcpcd[508]: ps_root_recvmsg: Address already in use
Jul 24 14:52:38 legion dhcpcd[508]: wlp0s20f3: DHCP6 proxy 2a02:8071:2180:c0:9ff2:48af:54c8:518 exited unexpectedly from PID 2966204, code=1
Jul 24 14:52:40 legion dbus-daemon[498]: [system] Activating via systemd: service name='org.freedesktop.home1' unit='dbus-org.freedesktop.home1.service' requested by ':1.2614' (uid=0 pid=2966>
Jul 24 14:52:40 legion dbus-daemon[498]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.home1.service': Unit dbus-org.freedesktop.home1.service not found.

If possible, I would like to avoid running chown -R over all of my data, since I believe these changes would be persisted and might even change timestamps?
Not sure about that, but any help in getting the mount option to work or "chowning temporarily" would be appreciated.

Last edited by mbw (2023-07-25 08:23:33)

Scimmia

Fellow

Registered: 2012-09-01

Posts: 13,727

Re: [Solved] Mounting LUKS-encrypted partition with uid,guid mount options

AFAIK, uid and gid mount options are only for filesystems that don't support POSIX permissions. It's not going to work like you want on ext4.

loqs

Member

Registered: 2014-03-06

Posts: 18,932

Re: [Solved] Mounting LUKS-encrypted partition with uid,guid mount options

Have you looked at the X-mount.owner X-mount.mode and X-mount.idmap options to mount?

mbw

Member

Registered: 2020-01-04

Posts: 38

Re: [Solved] Mounting LUKS-encrypted partition with uid,guid mount options

AFAIK, uid and gid mount options are only for filesystems that don't support POSIX permissions. It's not going to work like you want on ext4.

D'oh! You're right, I should read man pages more thoroughly...

Have you looked at the X-mount.owner X-mount.mode and X-mount.idmap options to mount?

I just tried the following:

$ sudo mount -o ro,X-mount.owner=$(id -u),X-mount.group=$(id -g) /dev/mapper/backup-disk /mnt/borg/
mount: /mnt/borg: filesystem was mounted, but failed to change ownership: Read-only file system.

So I believe, mounting without -o ro would probably work, but actually change permissions, i.e. write to disk.

I also just saw reference to bindfs right here: https://superuser.com/questions/519824/ … permission.

So I guess I am going to try this next. A one-shot "sudo mount -o bind,ro,uid=1000,gid=1000 /mnt/backup/ /mnt/borg/" to re-mount with different permissions didn't work either.

Edit: Ah wait, haven't tried idmap yet, sorry.

Last edited by mbw (2023-07-24 14:18:11)

mbw

Member

Registered: 2020-01-04

Posts: 38

Re: [Solved] Mounting LUKS-encrypted partition with uid,guid mount options

Okay, while X-mount.idmap is certainly promising, I am unfortunately stuck getting this to work.

The syntax is supposed to be 'X-mount.idmap=id-type:id-mount:id-host:id-range [id-type:id-mount:id-host:id-range]' and the following example is provided in mount (8):

For example, the ID-mapping X-mount.idmap=u:1000:0:1 g:1001:1:2 5000:1000:2 creates an idmapped mount where UID 0 is mapped to UID 1000, GID 1 is mapped to GUID 1001, GID 2
               is mapped to GID 1002, UID and GID 1000 are mapped to 5000, and UID and GID 1001 are mapped to 5001 in the mount.

According to this open issue, no implicit identity mapping is assumed: https://github.com/util-linux/util-linux/issues/2175

Thus I need to map both "0 --> 1000" and "1000 --> 1000" and I tried the following:

$ sudo mount -o ro,X-mount.idmap='u:1000:1000:1 g:1000:1000:1 u:1000:0:1 g:1000:0:1' /dev/mapper/backup-disk /home/mbw/testdir/mnt/
mount: /home/mbw/testdir/mnt/: failed to parse mount options 'ro,X-mount.idmap=u:1000:1000:1 g:1000:1000:1 u:1000:0:1 g:1000:0:1': Invalid argument.

And some syntactic variations like "b:1000:1000:1" or "1000:1000:1" which should be equivalent.
Likewise, providing X-mount.idmap multiple times isn't correct either since only one argument occurrence is taken into consideration.

How am I supposed to call this?

Last edited by mbw (2023-07-24 15:36:22)

mbw

Member

Registered: 2020-01-04

Posts: 38

Re: [Solved] Mounting LUKS-encrypted partition with uid,guid mount options

Ok, I asked in the GitHub issue and it turns out you can not map multiple uids to the same host uid.

I think my whole approach was misguided from the start anyway.
I looked into it some more and I think all files for which this actually matters reside in a Borg repository by now.
As such, what matters is how I mount said repository, and for this, using

sudo borg mount -o ro,allow_other /path/to/borg/repo /mnt/borg  # See `man mount.fuse`.

seems to do what I want.