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