root@ubuntu-jammy:~# strace -f -o log -s10000  mariabackup --prepare --target-dir=/mnt/X

mariabackup based on MariaDB server 10.9.4-MariaDB debian-linux-gnu (x86_64)

[00] 2022-12-19 07:59:12 cd to /mnt/X/

[00] 2022-12-19 07:59:12 open files limit requested 0, set to 1024

[00] 2022-12-19 07:59:12 This target seems to be not prepared yet.

[00] 2022-12-19 07:59:12 mariabackup: using the following InnoDB configuration for recovery:

[00] 2022-12-19 07:59:12 innodb_data_home_dir = .

[00] 2022-12-19 07:59:12 innodb_data_file_path = ibdata1:12M:autoextend

[00] 2022-12-19 07:59:12 innodb_log_group_home_dir = .

[00] 2022-12-19 07:59:12 Starting InnoDB instance for recovery.

[00] 2022-12-19 07:59:12 mariabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter)

2022-12-19  7:59:12 0 [Note] InnoDB: Compressed tables use zlib 1.2.11

2022-12-19  7:59:12 0 [Note] InnoDB: Number of transaction pools: 1

2022-12-19  7:59:12 0 [Note] InnoDB: Using crc32 + pclmulqdq instructions

2022-12-19  7:59:12 0 [Note] InnoDB: Initializing buffer pool, total size = 100.000MiB, chunk size = 100.000MiB

2022-12-19  7:59:12 0 [Note] InnoDB: Completed initialization of buffer pool

[00] 2022-12-19 07:59:12 mariadb-backup: srv_start() returned 100 (I/O error).

2434  openat(AT_FDCWD, "./ibdata1", O_RDWR|O_CLOEXEC <unfinished ...>

2434  <... openat resumed>)             = 6

2434  fcntl(6, F_SETFL, O_RDONLY|O_DIRECT <unfinished ...>

2434  <... fcntl resumed>)              = 0

2434  fcntl(6, F_SETLK, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0

2434  newfstatat(6, "", {st_mode=S_IFREG|0755, st_size=12582912, ...}, AT_EMPTY_PATH) = 0

2434  pread64(6, 0x55af89b64000, 65536, 0) = -1 EINVAL (Invalid argument)

2434  newfstatat(AT_FDCWD, "/etc/localtime", {st_mode=S_IFREG|0644, st_size=114, ...}, 0) = 0

2434  write(2, "[00] 2022-12-19 07:59:12 mariadb-backup: srv_start() returned 100 (I/O error).\n", 79) = 79