Re: lvm commands hanging when run from inside a kubernetes pod

You need to rerun with an "strace -f".  That way it will also strace the
fork's one of which it appears to be waiting on.

On Mon, May 30, 2022 at 1:52 AM Abhishek Agarwal <
[email protected]> wrote:

> When a kubernetes pod is scheduled on the node having lvm2 libraries
> already installed and trying to run lvm commands using those node binaries
> from inside the pod container, the commands hang and are waiting on
> something to complete. Although when ctrl+c is pressed the terminal session
> resumes and checking the final code for the execution returns a "0" error
> code and the commands operation is also carried out successfully.
>
>
> Below is the command output and strace for the command:-
>
> strace of lvcreate on the pod container scheduled on the node where lvm2
> binaries are present:
> # strace /sbin/lvm-eg/lvcreate -n test-lv -L 1G shared-vg
> execve("/sbin/lvm-eg/lvcreate", ["/sbin/lvm-eg/lvcreate", "-n", "test-lv",
> "-L", "1G", "shared-vg"], 0x7ffe7d7a6c98 /* 37 vars */) = 0
> brk(NULL)                = 0x55d196f41000
> arch_prctl(0x3001 /* ARCH_??? */, 0x7ffdd8247a80) = -1 EINVAL (Invalid
> argument)
> 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=8679, ...}) = 0
> mmap(NULL, 8679, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f0d37895000
> 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\360A\2\0\0\0\0\0"..., 832)
> = 832
> pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"...,
> 784, 64) = 784
> pread64(3,
> "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32,
> 848) = 32
> pread64(3,
> "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\237\333t\347\262\27\320l\223\27*\202C\370T\177"...,
> 68, 880) = 68
> fstat(3, {st_mode=S_IFREG|0755, st_size=2029560, ...}) = 0
> mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
> 0x7f0d37893000
> pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"...,
> 784, 64) = 784
> pread64(3,
> "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32,
> 848) = 32
> pread64(3,
> "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\237\333t\347\262\27\320l\223\27*\202C\370T\177"...,
> 68, 880) = 68
> mmap(NULL, 2037344, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) =
> 0x7f0d376a1000
> mmap(0x7f0d376c3000, 1540096, PROT_READ|PROT_EXEC,
> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7f0d376c3000
> mmap(0x7f0d3783b000, 319488, PROT_READ,
> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19a000) = 0x7f0d3783b000
> mmap(0x7f0d37889000, 24576, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f0d37889000
> mmap(0x7f0d3788f000, 13920, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f0d3788f000
> close(3)                = 0
> arch_prctl(ARCH_SET_FS, 0x7f0d37894580) = 0
> mprotect(0x7f0d37889000, 16384, PROT_READ) = 0
> mprotect(0x55d196662000, 8192, PROT_READ) = 0
> mprotect(0x7f0d378c5000, 4096, PROT_READ) = 0
> munmap(0x7f0d37895000, 8679)      = 0
> getuid()                = 0
> getgid()                = 0
> getpid()                = 19163
> rt_sigaction(SIGCHLD, {sa_handler=0x55d196657c30, sa_mask=~[RTMIN RT_1],
> sa_flags=SA_RESTORER, sa_restorer=0x7f0d376e40c0}, NULL, 8) = 0
> geteuid()                = 0
> brk(NULL)                = 0x55d196f41000
> brk(0x55d196f62000)           = 0x55d196f62000
> getppid()                = 19160
> stat("/", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
> stat(".", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
> openat(AT_FDCWD, "/sbin/lvm-eg/lvcreate", O_RDONLY) = 3
> fcntl(3, F_DUPFD, 10)          = 10
> close(3)                = 0
> fcntl(10, F_SETFD, FD_CLOEXEC)     = 0
> geteuid()                = 0
> getegid()                = 0
> rt_sigaction(SIGINT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0},
> 8) = 0
> rt_sigaction(SIGINT, {sa_handler=0x55d196657c30, sa_mask=~[RTMIN RT_1],
> sa_flags=SA_RESTORER, sa_restorer=0x7f0d376e40c0}, NULL, 8) = 0
> rt_sigaction(SIGQUIT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0},
> 8) = 0
> rt_sigaction(SIGQUIT, {sa_handler=SIG_DFL, sa_mask=~[RTMIN RT_1],
> sa_flags=SA_RESTORER, sa_restorer=0x7f0d376e40c0}, NULL, 8) = 0
> rt_sigaction(SIGTERM, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0},
> 8) = 0
> rt_sigaction(SIGTERM, {sa_handler=SIG_DFL, sa_mask=~[RTMIN RT_1],
> sa_flags=SA_RESTORER, sa_restorer=0x7f0d376e40c0}, NULL, 8) = 0
> read(10, "#!/bin/sh\npath=$(/sbin/lvm-eg/ge"..., 8192) = 79
> pipe([3, 4])              = 0
> clone(child_stack=NULL,
> flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
> child_tidptr=0x7f0d37894850) = 19164
> close(4)                = 0
> read(3, "/usr/sbin/lvcreate\n", 128)  = 19
> --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=19164, si_uid=0,
> si_status=0, si_utime=0, si_stime=0} ---
> rt_sigreturn({mask=[]})         = 19
> read(3, "", 128)            = 0
> close(3)                = 0
> wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 19164
> stat("/usr/local/sbin/chroot", 0x7ffdd8247710) = -1 ENOENT (No such file
> or directory)
> stat("/usr/local/bin/chroot", 0x7ffdd8247710) = -1 ENOENT (No such file or
> directory)
> stat("/usr/sbin/chroot", {st_mode=S_IFREG|0755, st_size=43352, ...}) = 0
> clone(child_stack=NULL,
> flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
> child_tidptr=0x7f0d37894850) = 19168
> wait4(-1, ^Cstrace: Process 19163 detached
>  <detached ...>
>
> # ^C
>
> `lvs` output on the node after pressing ctrl+c on the pod
> container's terminal:
> ubuntu@ip-172-31-85-197:~$ sudo lvs
>  LV                    VG       Attr    LSize  Pool      Origin Data%
> Meta% Move Log Cpy%Sync Convert
>  test-lv                 shared-vg    -wi-a-----  1.00g
>
> If ctrl+c is not pressed and trying to see the above output on the node
> also hangs until the pod operation is interrupted.
> _______________________________________________
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> [email protected]
> https://listman.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

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