the problem happened when I tried to install ubuntu using ZFS this issue doesn't happened when i used LVM...
>>>>>>>>>>>>>> this is the error massage and trace back
Jun 2 00:35:29 ubuntu ubiquity: AssertionError: Failed to mount the target: /target
Jun 2 00:35:40 ubuntu ubiquity: XDG_RUNTIME_DIR (/run/user/999) is not owned by us (uid 0), but by uid 999! (This could e.g. happen if you try to connect to a non-root PulseAudio as a root user, over the native protocol. Don't do that.)
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubiquity 20.04.15
ProcVersionSignature: Ubuntu 5.4.0-26.30-generic 5.4.30
Uname: Linux 5.4.0-26-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.445
Date: Tue Jun 2 03:35:40 2020
InstallCmdLine: file=/preseed/ubuntu.seed noprompt boot=casper iso-scan/filename=/ubuntu-20.04-desktop-amd64.iso quiet acpi=off --
LiveMediaBuild: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)
Jun 2 00:35:26 ubuntu ubiquity: I: Checking system requirements
Jun 2 00:35:26 ubuntu ubiquity: I: Running zsys-setup init
Jun 2 00:35:26 ubuntu ubiquity: I: Partition table before init of ZFS
Jun 2 00:35:26 ubuntu ubiquity: NR START END SECTORS SIZE NAME UUID
Jun 2 00:35:26 ubuntu ubiquity: 1 2048 1050623 1048576 512M eb40ea43-01
Jun 2 00:35:26 ubuntu ubiquity: 2 1052670 625141759 624089090 297.6G eb40ea43-02
Jun 2 00:35:26 ubuntu ubiquity: 5 1052672 625141759 624089088 297.6G eb40ea43-05
Jun 2 00:35:26 ubuntu ubiquity: I: Found swapfile with size 2147483648. Disabling
Jun 2 00:35:26 ubuntu systemd[1506]: target-
Jun 2 00:35:26 ubuntu systemd[1]: target-
Jun 2 00:35:26 ubuntu ubiquity: I: Saving existing fstab
Jun 2 00:35:26 ubuntu ubiquity: I: umounting /target/boot/efi
Jun 2 00:35:26 ubuntu systemd[1506]: target-
Jun 2 00:35:26 ubuntu systemd[1]: target-
Jun 2 00:35:26 ubuntu ubiquity: I: umounting /target
Jun 2 00:35:26 ubuntu systemd[1506]: target.mount: Succeeded.
Jun 2 00:35:26 ubuntu systemd[1]: target.mount: Succeeded.
Jun 2 00:35:27 ubuntu ubiquity: I: Formatting disk /dev/sda with partitions ESP:1 ext:2 swap:5 bpool:6 rpool:7
Jun 2 00:35:27 ubuntu kernel: [ 1332.052943] sda: sda1 sda2 < >
Jun 2 00:35:27 ubuntu ubiquity:
Jun 2 00:35:27 ubuntu ubiquity: The partition table has been altered.
Jun 2 00:35:27 ubuntu ubiquity: Calling ioctl() to re-read partition table.
Jun 2 00:35:27 ubuntu ubiquity: Syncing disks.
Jun 2 00:35:27 ubuntu kernel: [ 1332.072562] sda: sda1 sda2 < >
Jun 2 00:35:27 ubuntu ubiquity: Checking that no-one is using this disk right now ... OK
Jun 2 00:35:27 ubuntu ubiquity:
Jun 2 00:35:27 ubuntu ubiquity: Disk /dev/sda: 298.9 GiB, 320072933376 bytes, 625142448 sectors
Jun 2 00:35:27 ubuntu ubiquity: Disk model: HGST HTS725032A7
Jun 2 00:35:27 ubuntu ubiquity: Units: sectors of 1 * 512 = 512 bytes
Jun 2 00:35:27 ubuntu ubiquity: Sector size (logical/physical): 512 bytes / 4096 bytes
Jun 2 00:35:27 ubuntu ubiquity: I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Jun 2 00:35:27 ubuntu ubiquity: Disklabel type: dos
Jun 2 00:35:27 ubuntu ubiquity: Disk identifier: 0xeb40ea43
Jun 2 00:35:27 ubuntu ubiquity:
Jun 2 00:35:27 ubuntu ubiquity: Old situation:
Jun 2 00:35:27 ubuntu ubiquity:
Jun 2 00:35:27 ubuntu ubiquity: Device Boot Start End Sectors Size Id Type
Jun 2 00:35:27 ubuntu ubiquity: /dev/sda1 2048 1050623 1048576 512M b W95 FAT32
Jun 2 00:35:27 ubuntu ubiquity: /dev/sda2 1052670 625141759 624089090 297.6G 5 Extended
Jun 2 00:35:27 ubuntu ubiquity:
Jun 2 00:35:27 ubuntu ubiquity: Partition 2 does not start on physical sector boundary.
Jun 2 00:35:27 ubuntu ubiquity:
Jun 2 00:35:27 ubuntu kernel: [ 1332.074228] sda: sda1 sda2 < >
Jun 2 00:35:28 ubuntu ubiquity:
Jun 2 00:35:28 ubuntu ubiquity: /dev/sda3: Created a new partition 5 of type 'Linux swap / Solaris' and of size 2 GiB.
Jun 2 00:35:28 ubuntu ubiquity: /dev/sda6: Created a new partition 6 of type 'FreeBSD' and of size 2 GiB...