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Description of problem: dracut can not automatically find LVM1 root volume, which has ID_FS_TYPE=ext3 (in my case). Version-Release number of selected component (if applicable): Problem exists in my opinion since initramfs was generated with dracut. Current versions: dracut-011-0.1.git9b30d47.fc16.i686 grubby-7.0.18-1.fc16.i686 kernel-3.0-0.rc6.git6.1.fc16.i686 How reproducible: Always. Steps to Reproduce: 1. execute new-kernel-pkg as in installation script of kernel rpm 2. reboot 3. Actual results: Boot fails, because dracut can not find root device and exits into dracut shell. Expected results: dracut should find root device and boot from it. Additional info: Logical volume was generated with lvm1 a long time ago. Volume Group is of LVM2 format (according to vgdisplay). blkid -o udev -p <root-device> shows: ID_FS_TYPE=ext3 dracut only accepts LVM volumes with: ID_FS_TYPE="LVM?_member" Root device can be found and booted from if either: 1. entering the folowing in dracut shell after boot fails: # lvm_scan # exit 2. dracut 64-lvm.rules file changed to (in my case): ENV{ID_FS_TYPE}!="ext3", GOTO="lvm_end"
Do you want to say that blkid(8) returns "ext3", but the device is has LVM signature? Please, I'd like to see: # rpm -qf /sbin/blkid # BLKID_DEBUG=0xffff blkid -o udev -p <device> # hexdump -C -n 1000 <device>
Hello Karel as requested the additional information: # rpm -qf /sbin/blkid util-linux-2.19.1-2.fc16.i686 # BLKID_DEBUG=0xffff blkid -o udev -p /dev/mapper/vg0-root libblkid: debug mask set to 0xffff. ready for low-probing, offset=0, size=23228055552 found entire diskname for devno 0xfd00 as dm-0 whole-disk: YES, regfile: NO zeroize wiper chain safeprobe superblocks ENABLED --> starting probing loop [SUBLKS idx=-1] [0] linux_raid_member: call probefunc() buffer read: off=23227990016 len=64 buffer read: off=23228047360 len=256 buffer read: off=0 len=256 buffer read: off=4096 len=256 [1] ddf_raid_member: call probefunc() buffer read: off=23228055040 len=512 buffer read: off=23227923968 len=512 [2] isw_raid_member: call probefunc() buffer read: off=23228054528 len=48 [3] lsi_mega_raid_member: call probefunc() reuse buffer: off=23228055040 len=512 [4] via_raid_member: call probefunc() reuse buffer: off=23228055040 len=512 [5] silicon_medley_raid_member: call probefunc() reuse buffer: off=23228055040 len=512 [6] nvidia_raid_member: call probefunc() reuse buffer: off=23228054528 len=48 [7] promise_fasttrack_raid_member: call probefunc() buffer read: off=23228023296 len=24 buffer read: off=23227924992 len=24 buffer read: off=23227924480 len=24 reuse buffer: off=23228047360 len=256 buffer read: off=23227851264 len=24 [8] hpt45x_raid_member: call probefunc() buffer read: off=23228049920 len=4 [9] hpt37x_raid_member: buffer read: off=4096 len=1024 reuse buffer: off=4096 len=1024 [10] adaptec_raid_member: call probefunc() reuse buffer: off=23228055040 len=512 [11] jmicron_raid_member: call probefunc() reuse buffer: off=23228055040 len=512 [12] drbd: call probefunc() buffer read: off=23228051456 len=4096 [13] LVM2_member: buffer read: off=0 len=1024 reuse buffer: off=0 len=1024 buffer read: off=1024 len=1024 reuse buffer: off=1024 len=1024 [14] LVM1_member: reuse buffer: off=0 len=1024 [15] DM_snapshot_cow: reuse buffer: off=0 len=1024 [16] crypto_LUKS: reuse buffer: off=0 len=1024 [17] VMFS_volume_member: buffer read: off=1048576 len=1024 [18] vfat: reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 [19] swsuspend: reuse buffer: off=0 len=1024 buffer read: off=3072 len=1024 reuse buffer: off=3072 len=1024 reuse buffer: off=3072 len=1024 reuse buffer: off=3072 len=1024 buffer read: off=7168 len=1024 reuse buffer: off=7168 len=1024 reuse buffer: off=7168 len=1024 reuse buffer: off=7168 len=1024 buffer read: off=15360 len=1024 reuse buffer: off=15360 len=1024 reuse buffer: off=15360 len=1024 reuse buffer: off=15360 len=1024 buffer read: off=31744 len=1024 reuse buffer: off=31744 len=1024 reuse buffer: off=31744 len=1024 reuse buffer: off=31744 len=1024 buffer read: off=64512 len=1024 reuse buffer: off=64512 len=1024 reuse buffer: off=64512 len=1024 reuse buffer: off=64512 len=1024 [20] swap: reuse buffer: off=3072 len=1024 reuse buffer: off=3072 len=1024 reuse buffer: off=7168 len=1024 reuse buffer: off=7168 len=1024 reuse buffer: off=15360 len=1024 reuse buffer: off=15360 len=1024 reuse buffer: off=31744 len=1024 reuse buffer: off=31744 len=1024 reuse buffer: off=64512 len=1024 reuse buffer: off=64512 len=1024 [21] xfs: reuse buffer: off=0 len=1024 [22] ext4dev: reuse buffer: off=1024 len=1024 magic sboff=56, kboff=1 call probefunc() reuse buffer: off=1024 len=1024 [23] ext4: reuse buffer: off=1024 len=1024 magic sboff=56, kboff=1 call probefunc() reuse buffer: off=1024 len=1024 [24] ext3: reuse buffer: off=1024 len=1024 magic sboff=56, kboff=1 call probefunc() reuse buffer: off=1024 len=1024 ext2_sb.compat = 0000003C:00000006:00000003 assigning UUID [superblocks] assigning VERSION [superblocks] assigning TYPE [superblocks] assigning USAGE [superblocks] <-- leaving probing loop (type=ext3) [SUBLKS idx=24] --> starting probing loop [SUBLKS idx=24] [25] ext2: reuse buffer: off=1024 len=1024 magic sboff=56, kboff=1 call probefunc() reuse buffer: off=1024 len=1024 [26] jbd: reuse buffer: off=1024 len=1024 magic sboff=56, kboff=1 call probefunc() reuse buffer: off=1024 len=1024 [27] reiserfs: buffer read: off=8192 len=1024 buffer read: off=65536 len=1024 reuse buffer: off=65536 len=1024 reuse buffer: off=65536 len=1024 reuse buffer: off=8192 len=1024 [28] reiser4: reuse buffer: off=65536 len=1024 [29] jfs: buffer read: off=32768 len=1024 [30] udf: reuse buffer: off=32768 len=1024 reuse buffer: off=32768 len=1024 reuse buffer: off=32768 len=1024 reuse buffer: off=32768 len=1024 reuse buffer: off=32768 len=1024 reuse buffer: off=32768 len=1024 reuse buffer: off=32768 len=1024 [31] iso9660: reuse buffer: off=32768 len=1024 reuse buffer: off=32768 len=1024 [32] zfs_member: call probefunc() buffer read: off=131072 len=41 buffer read: off=135168 len=41 buffer read: off=139264 len=41 buffer read: off=143360 len=41 buffer read: off=147456 len=41 buffer read: off=151552 len=41 buffer read: off=155648 len=41 buffer read: off=159744 len=41 buffer read: off=163840 len=41 buffer read: off=167936 len=41 buffer read: off=172032 len=41 buffer read: off=176128 len=41 buffer read: off=180224 len=41 buffer read: off=184320 len=41 buffer read: off=188416 len=41 buffer read: off=192512 len=41 buffer read: off=196608 len=41 buffer read: off=200704 len=41 buffer read: off=204800 len=41 buffer read: off=208896 len=41 buffer read: off=212992 len=41 buffer read: off=217088 len=41 buffer read: off=221184 len=41 buffer read: off=225280 len=41 buffer read: off=229376 len=41 buffer read: off=233472 len=41 buffer read: off=237568 len=41 buffer read: off=241664 len=41 buffer read: off=245760 len=41 buffer read: off=249856 len=41 buffer read: off=253952 len=41 buffer read: off=258048 len=41 buffer read: off=393216 len=41 buffer read: off=397312 len=41 buffer read: off=401408 len=41 buffer read: off=405504 len=41 buffer read: off=409600 len=41 buffer read: off=413696 len=41 buffer read: off=417792 len=41 buffer read: off=421888 len=41 buffer read: off=425984 len=41 buffer read: off=430080 len=41 buffer read: off=434176 len=41 buffer read: off=438272 len=41 buffer read: off=442368 len=41 buffer read: off=446464 len=41 buffer read: off=450560 len=41 buffer read: off=454656 len=41 buffer read: off=458752 len=41 buffer read: off=462848 len=41 buffer read: off=466944 len=41 buffer read: off=471040 len=41 buffer read: off=475136 len=41 buffer read: off=479232 len=41 buffer read: off=483328 len=41 buffer read: off=487424 len=41 buffer read: off=491520 len=41 buffer read: off=495616 len=41 buffer read: off=499712 len=41 buffer read: off=503808 len=41 buffer read: off=507904 len=41 buffer read: off=512000 len=41 buffer read: off=516096 len=41 buffer read: off=520192 len=41 [33] hfsplus: reuse buffer: off=1024 len=1024 reuse buffer: off=1024 len=1024 reuse buffer: off=1024 len=1024 [34] hfs: reuse buffer: off=1024 len=1024 [35] ufs: call probefunc() buffer read: off=0 len=1377 buffer read: off=8192 len=1377 buffer read: off=65536 len=1377 buffer read: off=262144 len=1377 [36] hpfs: reuse buffer: off=8192 len=1024 [37] sysv: call probefunc() reuse buffer: off=0 len=1024 buffer read: off=9728 len=512 reuse buffer: off=15360 len=1024 buffer read: off=18944 len=512 [38] xenix: buffer read: off=2048 len=1024 reuse buffer: off=2048 len=1024 [39] ntfs: reuse buffer: off=0 len=1024 [40] cramfs: reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 [41] romfs: reuse buffer: off=0 len=1024 [42] minix: reuse buffer: off=1024 len=1024 reuse buffer: off=1024 len=1024 reuse buffer: off=1024 len=1024 reuse buffer: off=1024 len=1024 reuse buffer: off=1024 len=1024 [43] gfs: reuse buffer: off=65536 len=1024 [44] gfs2: reuse buffer: off=65536 len=1024 [45] ocfs: reuse buffer: off=8192 len=1024 [46] ocfs2: reuse buffer: off=1024 len=1024 reuse buffer: off=2048 len=1024 reuse buffer: off=4096 len=1024 reuse buffer: off=8192 len=1024 [47] oracleasm: reuse buffer: off=0 len=1024 [48] vxfs: reuse buffer: off=1024 len=1024 [49] squashfs: reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 [50] nss: reuse buffer: off=4096 len=1024 [51] btrfs: reuse buffer: off=65536 len=1024 [52] ubifs: reuse buffer: off=0 len=1024 [53] bfs: reuse buffer: off=0 len=1024 [54] VMFS: buffer read: off=2097152 len=1024 [55] befs: reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 [56] nilfs2: reuse buffer: off=1024 len=1024 [57] exfat: reuse buffer: off=0 len=1024 <-- leaving probing loop (failed) [SUBLKS idx=57] chain safeprobe topology DISABLED chain safeprobe partitions ENABLED --> starting probing loop [PARTS idx=-1] reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 gpt: ---> call probefunc() reuse buffer: off=0 len=1024 gpt: <--- (rc = 1) reuse buffer: off=0 len=1024 ultrix: ---> call probefunc() reuse buffer: off=15360 len=1024 ultrix: <--- (rc = 1) reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 buffer read: off=28672 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 <-- leaving probing loop (failed) [PARTS idx=10] zeroize wiper returning UUID value ID_FS_UUID=f23f728c-ade9-4558-8833-b3ec10168331 ID_FS_UUID_ENC=f23f728c-ade9-4558-8833-b3ec10168331 returning VERSION value ID_FS_VERSION=1.0 returning TYPE value ID_FS_TYPE=ext3 returning USAGE value ID_FS_USAGE=filesystem reseting probing buffers buffers summary: 30616 bytes by 98 read() call(s) # hexdump -C -n 1000 /dev/mapper/vg0-root 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000003e0 00 00 00 00 00 00 00 00 |........| 000003e8
you should run this on the physical volumes, which are part of the volume group.
Hello Harald sorry, didn't know to run it on PV. Ok, here it is. /dev/sda4 is the only PV of VG vg0 with the root LV. # BLKID_DEBUG=0xffff blkid -o udev -p /dev/sda4 libblkid: debug mask set to 0xffff. ready for low-probing, offset=0, size=25383214080 found entire diskname for devno 0x0804 as sda whole-disk: NO, regfile: NO zeroize wiper chain safeprobe superblocks ENABLED --> starting probing loop [SUBLKS idx=-1] [0] linux_raid_member: call probefunc() buffer read: off=25383141376 len=64 buffer read: off=25383202816 len=256 buffer read: off=0 len=256 buffer read: off=4096 len=256 [1] ddf_raid_member: call probefunc() buffer read: off=25383213568 len=512 buffer read: off=25383082496 len=512 [2] isw_raid_member: call probefunc() [3] lsi_mega_raid_member: call probefunc() [4] via_raid_member: call probefunc() [5] silicon_medley_raid_member: call probefunc() [6] nvidia_raid_member: call probefunc() [7] promise_fasttrack_raid_member: call probefunc() [8] hpt45x_raid_member: call probefunc() [9] hpt37x_raid_member: buffer read: off=4096 len=1024 reuse buffer: off=4096 len=1024 [10] adaptec_raid_member: call probefunc() [11] jmicron_raid_member: call probefunc() [12] drbd: call probefunc() buffer read: off=25383209984 len=4096 [13] LVM2_member: buffer read: off=0 len=1024 magic sboff=536, kboff=0 call probefunc() reuse buffer: off=0 len=1024 assigning UUID [superblocks] assigning VERSION [superblocks] wiper set to superblocks::LVM2_member off=0 size=8192 assigning TYPE [superblocks] assigning USAGE [superblocks] <-- leaving probing loop (type=LVM2_member) [SUBLKS idx=13] chain safeprobe topology DISABLED chain safeprobe partitions ENABLED --> starting probing loop [PARTS idx=-1] reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 magic sboff=510, kboff=0 dos: ---> call probefunc() reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 magic sboff=0, kboff=0 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 wiped area detected -- ignore previous results zeroize wiper dos: <--- (rc = 0) assigning PTTYPE [partitions] <-- leaving probing loop (type=dos) [PARTS idx=3] found devno 0x0800 as /dev/sda parts: 8:4: starting whole-disk probing: /dev/sda ready for low-probing, offset=0, size=120034123776 found entire diskname for devno 0x0800 as sda whole-disk: YES, regfile: NO partlist reseted parts: initialized partitions list (0x924c328, size=0) --> starting probing loop [PARTS idx=-1] buffer read: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 magic sboff=510, kboff=0 dos: ---> call probefunc() reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 magic sboff=0, kboff=0 reuse buffer: off=0 len=1024 reuse buffer: off=0 len=1024 parts: create a new partition table (0x924c768, type=dos, offset=446) parts: add partition (0x924c788 start=63, size=12578832, table=0x924c768) parts: add partition (0x924c87c start=12578895, size=62878410, table=0x924c768) parts: add partition (0x924c970 start=75473370, size=107426655, table=0x924c768) parts: add partition (0x924ca64 start=184859955, size=49576590, table=0x924c768) dos: <--- (rc = 0) <-- leaving probing loop (type=dos) [PARTS idx=3] returning partitions binary data assigning PART_ENTRY_SCHEME [partitions] assigning PART_ENTRY_TYPE [partitions] assigning PART_ENTRY_NUMBER [partitions] reseting probing buffers buffers summary: 1024 bytes by 1 read() call(s) zeroize wiper returning PTTYPE value ID_PART_TABLE_TYPE=dos returning PART_ENTRY_SCHEME value ID_PART_ENTRY_SCHEME=dos returning PART_ENTRY_TYPE value ID_PART_ENTRY_TYPE=0x8e returning PART_ENTRY_NUMBER value ID_PART_ENTRY_NUMBER=4 reseting probing buffers buffers summary: 8000 bytes by 9 read() call(s) # hexdump -C -n 1000 /dev/sda4 00000000 eb 4c 90 00 00 00 00 00 00 00 00 00 00 00 00 00 |.L..............| 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04 00 |................| 00000040 00 80 00 08 8f d6 ca 01 00 00 00 00 ff ff fa eb |................| 00000050 07 f6 c2 80 75 02 b2 80 ea 5d 7c 00 00 31 c0 8e |....u....]|..1..| 00000060 d8 8e d0 bc 00 20 fb a1 4c 7c 88 e6 3c ff 74 02 |..... ..L|..<.t.| 00000070 88 c2 52 be 76 7d e8 25 01 be 05 7c f6 c2 80 74 |..R.v}.%...|...t| 00000080 48 b4 41 bb aa 55 cd 13 5a 52 72 3d 81 fb 55 aa |H.A..U..ZRr=..U.| 00000090 75 37 83 e1 01 74 32 31 c0 89 44 04 40 88 44 ff |u7...t21..D.@.D.| 000000a0 89 44 02 c7 04 10 00 66 8b 1e 44 7c 66 89 5c 08 |.D.....f..D|f.\.| 000000b0 66 8b 1e 48 7c 66 89 5c 0c c7 44 06 00 70 b4 42 |f..H|f.\..D..p.B| 000000c0 cd 13 72 05 bb 00 70 eb 74 b4 08 cd 13 73 0a f6 |..r...p.t....s..| 000000d0 c2 80 0f 84 ed 00 e9 85 00 66 0f b6 c6 88 64 ff |.........f....d.| 000000e0 40 66 89 44 04 0f b6 d1 c1 e2 02 88 e8 88 f4 40 |@f.D...........@| 000000f0 89 44 08 0f b6 c2 c0 e8 02 66 89 04 66 a1 48 7c |.D.......f..f.H|| 00000100 66 09 c0 75 51 66 a1 44 7c 66 31 d2 66 f7 34 88 |f..uQf.D|f1.f.4.| 00000110 d1 31 d2 66 f7 74 04 3b 44 08 7d 3a fe c1 88 c5 |.1.f.t.;D.}:....| 00000120 30 c0 c1 e8 02 08 c1 88 d0 5a 52 88 c6 bb 00 70 |0........ZR....p| 00000130 8e c3 31 db b8 01 02 cd 13 72 2b 8c c3 8e 06 42 |..1......r+....B| 00000140 7c 60 1e b9 00 01 8e db 31 f6 31 ff fc f3 a5 1f ||`......1.1.....| 00000150 61 5a ff 26 40 7c be 7c 7d e8 42 00 eb 0e be 81 |aZ.&@|.|}.B.....| 00000160 7d e8 3a 00 eb 06 be 8b 7d e8 32 00 be 90 7d e8 |}.:.....}.2...}.| 00000170 2c 00 cd 18 eb fe 47 52 55 42 20 00 47 65 6f 6d |,.....GRUB .Geom| 00000180 00 48 61 72 64 20 44 69 73 6b 00 52 65 61 64 00 |.Hard Disk.Read.| 00000190 20 45 72 72 6f 72 00 bb 01 00 b4 0e cd 10 ac 3c | Error.........<| 000001a0 00 75 f4 c3 00 00 00 00 00 00 00 00 00 00 00 00 |.u..............| 000001b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.| 00000200 4c 41 42 45 4c 4f 4e 45 01 00 00 00 00 00 00 00 |LABELONE........| 00000210 7e 4f 25 21 20 00 00 00 4c 56 4d 32 20 30 30 31 |~O%! ...LVM2 001| 00000220 4c 4f 78 51 4d 78 6b 66 65 79 31 49 39 77 59 4e |LOxQMxkfey1I9wYN| 00000230 46 70 58 4e 4f 43 48 49 4d 61 51 51 4b 6d 6b 59 |FpXNOCHIMaQQKmkY| 00000240 00 1c f5 e8 05 00 00 00 00 00 03 00 00 00 00 00 |................| 00000250 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00000260 00 00 00 00 00 00 00 00 00 10 00 00 00 00 00 00 |................| 00000270 00 f0 02 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00000280 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000003e0 00 00 00 00 00 00 00 00 |........| 000003e8
The blkid detects LVM2_MEMBER, but the result is ignored, because there is obsolete extended partition table on the device (line 00001f0 in the hexdump). It seems that pvcreate does not delete the first 512 bytes on the device ;-( I'll try to fix this heuristic, the current implementation is not robust... The workaround is to remove 0x55AA bytes, try: # dd if=/dev/zero of=/dev/sda4 seek=510 count=2 bs=1 conv=notrunc but be careful! Maybe you want to backup the begin of the device: # dd if=/dev/md1 of=/root/sda4.img count=1 bs=1MiB
(In reply to comment #5) > # dd if=/dev/md1 of=/root/sda4.img count=1 bs=1MiB ^^^^^^^^ /dev/sda4 sorry.
(In reply to comment #5) > The blkid detects LVM2_MEMBER, but the result is ignored, because there is > obsolete extended partition table on the device (line 00001f0 in the hexdump). > > It seems that pvcreate does not delete the first 512 bytes on the device ;-( This is probably not true. It seems that pvcreate delete the begin of the device. # hexdump -C -n 550 /dev/sdb2 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.| 00000200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000220 00 00 00 00 00 00 |......| 00000226 # pvcreate /dev/sdb2 Physical volume "/dev/sdb2" successfully created # hexdump -C -n 550 /dev/sdb2 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000200 4c 41 42 45 4c 4f 4e 45 01 00 00 00 00 00 00 00 |LABELONE........| 00000210 16 ae d8 78 20 00 00 00 4c 56 4d 32 20 30 30 31 |...x ...LVM2 001| 00000220 65 67 63 72 57 67 |egcrWg| 00000226
Well, verified in pvcreate code, by default it deletes the first 2048 bytes on the device. So the disk was modified (for example by fdisk) after pvcreate.
Hello Karel yes, that did the job. Thank you. :-) I wrote the two zero bytes with dd, changed the dracut 64-lvm.rules back to its original, re-created the initramfs, and rebooted the system. Now the root device was found without a problem. It is true that /dev/sda4 once was an extended partition. I tried it and, yes, an "fdisk /dev/sda4" with a write/exit changes the "00 00" back to "55 aa" at the noted position. But I can't remember when and even why I should have done an "fdisk /dev/sda4" and then quitting with a write/exit. Nonetheless, many thanks for your help. Best regards Dirk