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Re: virtual device both is and isn't a valid file system [complete]




Noticing the "write on read-only" error, and remembering it should be
read-only, I added that to the mount options.  Which still failed, but
differently:
root@barley:~/tempserver-check# date; strace -f mount -r
/dev/stretch-vg/boot stretch_boot
Tue 14 May 2019 10:07:05 AM PDT
execve("/usr/bin/mount", ["mount", "-r", "/dev/stretch-vg/boot",
"stretch_boot"], 0x7ffebd8055b0 /* 26 vars */) = 0
brk(NULL)                               = 0x55f1c537d000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=169946, ...}) = 0
mmap(NULL, 169946, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f292e2bf000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libmount.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\340\332\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=383456, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0x7f292e2bd000
mmap(NULL, 386344, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292e25e000
mprotect(0x7f292e26a000, 323584, PROT_NONE) = 0
mmap(0x7f292e26a000, 245760, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xc000) = 0x7f292e26a000
mmap(0x7f292e2a6000, 73728, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x48000) = 0x7f292e2a6000
mmap(0x7f292e2b9000, 16384, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x5a000) = 0x7f292e2b9000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libselinux.so.1",
O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0@k\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=155296, ...}) = 0
mmap(NULL, 2259632, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3,
0) = 0x7f292e036000
mprotect(0x7f292e05b000, 2093056, PROT_NONE) = 0
mmap(0x7f292e25a000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x24000) = 0x7f292e25a000
mmap(0x7f292e25c000, 6832, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f292e25c000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260A\2\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1824496, ...}) = 0
mmap(NULL, 1837056, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292de75000
mprotect(0x7f292de97000, 1658880, PROT_NONE) = 0
mmap(0x7f292de97000, 1343488, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7f292de97000
mmap(0x7f292dfdf000, 311296, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16a000) = 0x7f292dfdf000
mmap(0x7f292e02c000, 24576, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1b6000) = 0x7f292e02c000
mmap(0x7f292e032000, 14336, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f292e032000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libblkid.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\257\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=343008, ...}) = 0
mmap(NULL, 345896, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292de20000
mprotect(0x7f292de2a000, 282624, PROT_NONE) = 0
mmap(0x7f292de2a000, 212992, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xa000) = 0x7f292de2a000
mmap(0x7f292de5e000, 65536, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3e000) = 0x7f292de5e000
mmap(0x7f292de6f000, 24576, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x4e000) = 0x7f292de6f000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/librt.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260#\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=35808, ...}) = 0
mmap(NULL, 39904, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292de16000
mmap(0x7f292de18000, 16384, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f292de18000
mmap(0x7f292de1c000, 8192, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0x7f292de1c000
mmap(0x7f292de1e000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x7000) = 0x7f292de1e000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libpcre.so.3", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\340!\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=468944, ...}) = 0
mmap(NULL, 471304, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292dda2000
mmap(0x7f292dda4000, 335872, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f292dda4000
mmap(0x7f292ddf6000, 122880, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x54000) = 0x7f292ddf6000
mmap(0x7f292de14000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x71000) = 0x7f292de14000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libdl.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0000\21\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=14592, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0x7f292dda0000
mmap(NULL, 16656, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292dd9b000
mmap(0x7f292dd9c000, 4096, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0x7f292dd9c000
mmap(0x7f292dd9d000, 4096, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f292dd9d000
mmap(0x7f292dd9e000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f292dd9e000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libuuid.so.1", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0
#\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=30776, ...}) = 0
mmap(NULL, 32792, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292dd92000
mmap(0x7f292dd94000, 16384, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f292dd94000
mmap(0x7f292dd98000, 4096, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0x7f292dd98000
mmap(0x7f292dd99000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0x7f292dd99000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libpthread.so.0",
O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0@l\0\0\0\0\0\0"...,
832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=146968, ...}) = 0
mmap(NULL, 132288, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f292dd71000
mmap(0x7f292dd77000, 61440, PROT_READ|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6000) = 0x7f292dd77000
mmap(0x7f292dd86000, 24576, PROT_READ,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x15000) = 0x7f292dd86000
mmap(0x7f292dd8c000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1a000) = 0x7f292dd8c000
mmap(0x7f292dd8e000, 13504, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f292dd8e000
close(3)                                = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0x7f292dd6f000
arch_prctl(ARCH_SET_FS, 0x7f292dd70100) = 0
mprotect(0x7f292e02c000, 16384, PROT_READ) = 0
mprotect(0x7f292dd8c000, 4096, PROT_READ) = 0
mprotect(0x7f292dd99000, 4096, PROT_READ) = 0
mprotect(0x7f292dd9e000, 4096, PROT_READ) = 0
mprotect(0x7f292de14000, 4096, PROT_READ) = 0
mprotect(0x7f292de1e000, 4096, PROT_READ) = 0
mprotect(0x7f292de6f000, 20480, PROT_READ) = 0
mprotect(0x7f292e25a000, 4096, PROT_READ) = 0
mprotect(0x7f292e2b9000, 12288, PROT_READ) = 0
mprotect(0x55f1c3476000, 4096, PROT_READ) = 0
mprotect(0x7f292e310000, 4096, PROT_READ) = 0
munmap(0x7f292e2bf000, 169946)          = 0
set_tid_address(0x7f292dd703d0)         = 5197
set_robust_list(0x7f292dd703e0, 24)     = 0
rt_sigaction(SIGRTMIN, {sa_handler=0x7f292dd776b0, sa_mask=[],
sa_flags=SA_RESTORER|SA_SIGINFO, sa_restorer=0x7f292dd83730}, NULL, 8)
= 0
rt_sigaction(SIGRT_1, {sa_handler=0x7f292dd77740, sa_mask=[],
sa_flags=SA_RESTORER|SA_RESTART|SA_SIGINFO,
sa_restorer=0x7f292dd83730}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=9788*1024,
rlim_max=RLIM64_INFINITY}) = 0
statfs("/sys/fs/selinux", 0x7ffdd9fc4220) = -1 ENOENT (No such file or
directory)
statfs("/selinux", 0x7ffdd9fc4220)      = -1 ENOENT (No such file or directory)
brk(NULL)                               = 0x55f1c537d000
brk(0x55f1c539e000)                     = 0x55f1c539e000
openat(AT_FDCWD, "/proc/filesystems", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
read(3, "nodev\tsysfs\nnodev\trootfs\nnodev\tr"..., 1024) = 354
read(3, "", 1024)                       = 0
close(3)                                = 0
access("/etc/selinux/config", F_OK)     = 0
openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=5631424, ...}) = 0
mmap(NULL, 5631424, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f292d810000
close(3)                                = 0
getuid()                                = 0
geteuid()                               = 0
access("/sys/fs/smackfs", F_OK)         = -1 ENOENT (No such file or directory)
lstat("/dev", {st_mode=S_IFDIR|0755, st_size=5560, ...}) = 0
lstat("/dev/stretch-vg", {st_mode=S_IFDIR|0755, st_size=140, ...}) = 0
lstat("/dev/stretch-vg/boot", {st_mode=S_IFLNK|0777, st_size=8, ...}) = 0
readlink("/dev/stretch-vg/boot", "../dm-30", 4095) = 8
lstat("/dev/dm-30", {st_mode=S_IFBLK|0660, st_rdev=makedev(0xfd,
0x1e), ...}) = 0
stat("/dev/dm-30", {st_mode=S_IFBLK|0660, st_rdev=makedev(0xfd, 0x1e), ...}) = 0
openat(AT_FDCWD, "/sys/block/dm-30/dm/name", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
read(3, "stretch--vg-boot\n", 4096)     = 17
close(3)                                = 0
stat("/dev/mapper/stretch--vg-boot", {st_mode=S_IFBLK|0660,
st_rdev=makedev(0xfd, 0x1e), ...}) = 0
getcwd("/root/tempserver-check", 4096)  = 23
lstat("/root/tempserver-check/stretch_boot", {st_mode=S_IFDIR|0755,
st_size=4096, ...}) = 0
access("/dev/mapper/stretch--vg-boot", F_OK) = 0
openat(AT_FDCWD, "/dev/mapper/stretch--vg-boot", O_RDONLY|O_CLOEXEC) = 3
fadvise64(3, 0, 0, POSIX_FADV_RANDOM)   = 0
fstat(3, {st_mode=S_IFBLK|0660, st_rdev=makedev(0xfd, 0x1e), ...}) = 0
ioctl(3, BLKGETSIZE64, [398458880])     = 0
openat(AT_FDCWD, "/sys/dev/block/253:30", O_RDONLY|O_CLOEXEC) = 4
openat(4, "dm/uuid", O_RDONLY|O_CLOEXEC) = 5
read(5, "LVM-3dcV99ZH3Y7prfkBtGFmGKnAtnyQ"..., 8191) = 69
read(5, "", 8122)                       = 0
close(5)                                = 0
close(4)                                = 0
lseek(3, 398393344, SEEK_SET)           = 398393344
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
64) = 64
lseek(3, 398450688, SEEK_SET)           = 398450688
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
256) = 256
lseek(3, 0, SEEK_SET)                   = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
256) = 256
lseek(3, 4096, SEEK_SET)                = 4096
read(3, "\1\0\4\0\21\0\4\0!\0\4\0\364\17\256\6\4\0\4\0\0\0\0\0\251[gm\255\6l\33"...,
256) = 256
lseek(3, 398458368, SEEK_SET)           = 398458368
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
512) = 512
lseek(3, 398327296, SEEK_SET)           = 398327296
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
512) = 512
openat(AT_FDCWD, "/sys/dev/block/253:30", O_RDONLY|O_CLOEXEC) = 4
faccessat(4, "partition", F_OK)         = -1 ENOENT (No such file or directory)
openat(4, "dm/uuid", O_RDONLY|O_CLOEXEC) = 5
read(5, "LVM-3dcV99ZH3Y7prfkBtGFmGKnAtnyQ"..., 8191) = 69
read(5, "", 8122)                       = 0
close(5)                                = 0
close(4)                                = 0
ioctl(3, BLKSSZGET, [512])              = 0
lseek(3, 398457856, SEEK_SET)           = 398457856
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
48) = 48
lseek(3, 398426624, SEEK_SET)           = 398426624
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 398328320, SEEK_SET)           = 398328320
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 398327808, SEEK_SET)           = 398327808
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 398254592, SEEK_SET)           = 398254592
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 398156288, SEEK_SET)           = 398156288
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 398113280, SEEK_SET)           = 398113280
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 398082560, SEEK_SET)           = 398082560
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 397992448, SEEK_SET)           = 397992448
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 397960192, SEEK_SET)           = 397960192
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 397951488, SEEK_SET)           = 397951488
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 397971968, SEEK_SET)           = 397971968
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 396878336, SEEK_SET)           = 396878336
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 24) = 24
lseek(3, 398453248, SEEK_SET)           = 398453248
read(3, "\0\0\0\0", 4)                  = 4
lseek(3, 4096, SEEK_SET)                = 4096
read(3, "\1\0\4\0\21\0\4\0!\0\4\0\364\17\256\6\4\0\4\0\0\0\0\0\251[gm\255\6l\33"...,
1024) = 1024
lseek(3, 398454784, SEEK_SET)           = 398454784
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
4096) = 4096
lseek(3, 0, SEEK_SET)                   = 0
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3, 1024, SEEK_SET)                = 1024
read(3, "\0}\1\0\0\360\5\0\0L\0\0\223*\4\0\247{\1\0\1\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3, 16384, SEEK_SET)               = 16384
read(3, "\20 \0\0\20`\0\0\20\240\0\0\20\340\0\0\20 \1\0\20
\3\0\20`\3\0\0\0\0\0"..., 512) = 512
lseek(3, 32768, SEEK_SET)               = 32768
read(3, "  \0\0 `\0\0 \240\0\0 \340\0\0  \1\0  \3\0 `\3\0\0\0\0\0"...,
512) = 512
lseek(3, 65536, SEEK_SET)               = 65536
read(3, "@ \0\0@`\0\0@\240\0\0@\340\0\0@ \1\0@ \3\0@`\3\0\0\0\0\0"...,
512) = 512
lseek(3, 131072, SEEK_SET)              = 131072
read(3, "\200 \0\0\200`\0\0\200\240\0\0\200\340\0\0\200 \1\0\200
\3\0\200`\3\0\0\0\0\0"..., 512) = 512
lseek(3, 262144, SEEK_SET)              = 262144
read(3, "\0!\0\0\0a\0\0\0\241\0\0\0\341\0\0\0!\1\0\0!\3\0\0a\3\0\0\0\0\0"...,
512) = 512
lseek(3, 524288, SEEK_SET)              = 524288
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
512) = 512
lseek(3, 1048576, SEEK_SET)             = 1048576
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
512) = 512
lseek(3, 2097152, SEEK_SET)             = 2097152
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
512) = 512
lseek(3, 4194304, SEEK_SET)             = 4194304
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
512) = 512
lseek(3, 1048576, SEEK_SET)             = 1048576
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3, 3072, SEEK_SET)                = 3072
read(3, "\1\0\2\0\21\0\2\0!\0\2\0\0\20\360\7\0\0\5\0\0\0\0\0\355\267\0\0\360\7\262\32"...,
1024) = 1024
lseek(3, 7168, SEEK_SET)                = 7168
read(3, "\7 \0\0\7`\0\0\7\240\0\0\7\340\0\0\7 \1\0\7
\3\0\7`\3\0\0\0\0\0"..., 1024) = 1024
lseek(3, 15360, SEEK_SET)               = 15360
read(3, "\17 \0\0\17`\0\0\17\240\0\0\17\340\0\0\17 \1\0\17
\3\0\17`\3\0\0\0\0\0"..., 1024) = 1024
lseek(3, 31744, SEEK_SET)               = 31744
read(3, "\37 \0\0\37`\0\0\37\240\0\0\37\340\0\0\37 \1\0\37
\3\0\37`\3\0\0\0\0\0"..., 1024) = 1024
lseek(3, 64512, SEEK_SET)               = 64512
read(3, "? \0\0?`\0\0?\240\0\0?\340\0\0? \1\0? \3\0?`\3\0\0\0\0\0"...,
1024) = 1024
lseek(3, 0, SEEK_SET)                   = 0
mmap(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0x7f292d7cf000
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
262144) = 262144
lseek(3, 262144, SEEK_SET)              = 262144
mmap(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0x7f292d78e000
read(3, "\0!\0\0\0a\0\0\0\241\0\0\0\341\0\0\0!\1\0\0!\3\0\0a\3\0\0\0\0\0"...,
262144) = 262144
lseek(3, 397934592, SEEK_SET)           = 397934592
mmap(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0x7f292d74d000
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
262144) = 262144
lseek(3, 398196736, SEEK_SET)           = 398196736
mmap(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
-1, 0) = 0x7f292d70c000
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
262144) = 262144
lseek(3, 2097152, SEEK_SET)             = 2097152
read(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
close(3)                                = 0
munmap(0x7f292d7cf000, 266240)          = 0
munmap(0x7f292d78e000, 266240)          = 0
munmap(0x7f292d74d000, 266240)          = 0
munmap(0x7f292d70c000, 266240)          = 0
stat("/sbin/mount.ext4", 0x7ffdd9fc1f50) = -1 ENOENT (No such file or directory)
stat("/sbin/fs.d/mount.ext4", 0x7ffdd9fc1f50) = -1 ENOENT (No such
file or directory)
stat("/sbin/fs/mount.ext4", 0x7ffdd9fc1f50) = -1 ENOENT (No such file
or directory)
getuid()                                = 0
geteuid()                               = 0
getgid()                                = 0
getegid()                               = 0
prctl(PR_GET_DUMPABLE)                  = 1 (SUID_DUMP_USER)
stat("/run", {st_mode=S_IFDIR|0755, st_size=1240, ...}) = 0
lstat("/run/mount/utab", 0x7ffdd9fc3090) = -1 ENOENT (No such file or directory)
mkdir("/run/mount", 0755)               = -1 EEXIST (File exists)
stat("/run/mount/utab", 0x7ffdd9fc2f80) = -1 ENOENT (No such file or directory)
stat("/run/mount", {st_mode=S_IFDIR|0755, st_size=40, ...}) = 0
geteuid()                               = 0
getegid()                               = 0
getuid()                                = 0
getgid()                                = 0
access("/run/mount", R_OK|W_OK)         = 0
mount("/dev/mapper/stretch--vg-boot",
"/root/tempserver-check/stretch_boot", "ext4", MS_RDONLY, NULL) = 0
close(1)                                = 0
close(2)                                = 0
exit_group(0)                           = ?
+++ exited with 0 +++
root@barley:~/tempserver-check# dmesg | tail
[40566.133158] audit: type=1400 audit(1557817207.785:31):
apparmor="DENIED" operation="open" profile="/usr/sbin/cups-browsed"
name="/usr/share/cups/locale/" pid=23717 comm="cups-browsed"
requested_mask="r" denied_mask="r" fsuid=0 ouid=0
[40566.133186] audit: type=1400 audit(1557817207.785:32):
apparmor="DENIED" operation="open" profile="/usr/sbin/cups-browsed"
name="/usr/share/locale/" pid=23717 comm="cups-browsed"
requested_mask="r" denied_mask="r" fsuid=0 ouid=0
[60924.796860] perf: interrupt took too long (4974 > 4947), lowering
kernel.perf_event_max_sample_rate to 40000
[68155.285591] Process accounting resumed
[74940.130661] block nbd3: Write on read-only
[74940.130666] print_req_error: I/O error, dev nbd3, sector 22843394
[74940.130671] Buffer I/O error on dev dm-30, logical block 1, lost
sync page write
[74940.130677] EXT4-fs (dm-30): I/O error while writing superblock
[74940.130684] EXT4-fs (dm-30): mount failed
[76983.987331] EXT4-fs (dm-30): mounted filesystem with ordered data
mode. Opts: (null)

The bad sector was at 7,724,531,336, 8 sectors long, using 512b
sectors and decimal numbers.
The partition sdf2 starts at sector 4096 and ends at 7814035455.  Even
with all the layers, that doesn't seem to be the one reporting the
error.  And on sdf2 reading that location should not be a hardware
error, just junk data.

Ross