2019-10-10 CentOS 7.7のmv > StackOverflow掲載とは異なる動作 > シンボリックリンクは解除されない

```txt:動作環境
A. CentOS Linux release 7.7.1908 (Core)
B. StackOverflow掲載のOSは不明
```

### とっかかり

- ファイルのシンボリックリンクを外す方法を探していた
- StackOverflowにて「mvコマンドで十分」という記載があった
- CentOS 7.7でやったところ、十分でなかった

### mvの挙動 (CentOS 7.7)

- [Linux > strace > コマンド実行時の詳細を表示する > OSの違いによる振舞いの違い確認などに使えそう](https://qiita.com/7of9/items/e764bcc3cb23a8fe7d94)

StackOverflow (answered Sep 7 '16 at 23:29 by Kaz)
https://stackoverflow.com/questions/8377312/how-to-convert-symlink-to-regular-file

unlinkというのがある。

一方で、CentOS 7.7の場合（下記)には「unlink」はない。シンボリックリンクがはずれない理由なのだろう。

```
$ strace mv LN_TEST LN_TEST2
execve("/usr/bin/mv", ["mv", "LN_TEST", "LN_TEST2"], [/* 73 vars */]) = 0
brk(NULL)                               = 0x17bc000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fac0270c000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("tls/x86_64/libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("tls/libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("x86_64/libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/tls/x86_64/libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/usr/local/netcdf-4.7.1/gcc44/lib/tls/x86_64", 0x7ffdf098ce00) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/tls/libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/usr/local/netcdf-4.7.1/gcc44/lib/tls", 0x7ffdf098ce00) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/x86_64/libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/usr/local/netcdf-4.7.1/gcc44/lib/x86_64", 0x7ffdf098ce00) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/libselinux.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
stat("/usr/local/netcdf-4.7.1/gcc44/lib", {st_mode=S_IFDIR|0755, st_size=270, ...}) = 0
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=93690, ...}) = 0
mmap(NULL, 93690, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fac026f5000
close(3)                                = 0
open("/lib64/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\320i\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=155784, ...}) = 0
mmap(NULL, 2255184, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fac022c5000
mprotect(0x7fac022e9000, 2093056, PROT_NONE) = 0
mmap(0x7fac024e8000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x23000) = 0x7fac024e8000
mmap(0x7fac024ea000, 6480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fac024ea000
close(3)                                = 0
open("tls/x86_64/libacl.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("tls/libacl.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("x86_64/libacl.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("libacl.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/libacl.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib64/libacl.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\200\37\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=37056, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fac026f4000
mmap(NULL, 2130560, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fac020bc000
mprotect(0x7fac020c3000, 2097152, PROT_NONE) = 0
mmap(0x7fac022c3000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x7000) = 0x7fac022c3000
close(3)                                = 0
open("tls/x86_64/libattr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("tls/libattr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("x86_64/libattr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("libattr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/libattr.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib64/libattr.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\320\23\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=19896, ...}) = 0
mmap(NULL, 2113904, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fac01eb7000
mprotect(0x7fac01ebb000, 2093056, PROT_NONE) = 0
mmap(0x7fac020ba000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3000) = 0x7fac020ba000
close(3)                                = 0
open("tls/x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("tls/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("x86_64/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("libc.so.6", O_RDONLY|O_CLOEXEC)   = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib64/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\20&\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2156160, ...}) = 0
mmap(NULL, 3985888, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fac01ae9000
mprotect(0x7fac01cac000, 2097152, PROT_NONE) = 0
mmap(0x7fac01eac000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1c3000) = 0x7fac01eac000
mmap(0x7fac01eb2000, 16864, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fac01eb2000
close(3)                                = 0
open("tls/x86_64/libpcre.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("tls/libpcre.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("x86_64/libpcre.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("libpcre.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/libpcre.so.1", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib64/libpcre.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\360\25\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=402384, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fac026f3000
mmap(NULL, 2494984, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fac01887000
mprotect(0x7fac018e7000, 2097152, PROT_NONE) = 0
mmap(0x7fac01ae7000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x60000) = 0x7fac01ae7000
close(3)                                = 0
open("tls/x86_64/libdl.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("tls/libdl.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("x86_64/libdl.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("libdl.so.2", O_RDONLY|O_CLOEXEC)  = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/libdl.so.2", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib64/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\0\220\r\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=19288, ...}) = 0
mmap(NULL, 2109712, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fac01683000
mprotect(0x7fac01685000, 2097152, PROT_NONE) = 0
mmap(0x7fac01885000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7fac01885000
close(3)                                = 0
open("tls/x86_64/libpthread.so.0", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("tls/libpthread.so.0", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("x86_64/libpthread.so.0", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("libpthread.so.0", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/usr/local/netcdf-4.7.1/gcc44/lib/libpthread.so.0", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
open("/lib64/libpthread.so.0", 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@m\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=142232, ...}) = 0
mmap(NULL, 2208904, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fac01467000
mprotect(0x7fac0147e000, 2093056, PROT_NONE) = 0
mmap(0x7fac0167d000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16000) = 0x7fac0167d000
mmap(0x7fac0167f000, 13448, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fac0167f000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fac026f2000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fac026f0000
arch_prctl(ARCH_SET_FS, 0x7fac026f0840) = 0
mprotect(0x7fac01eac000, 16384, PROT_READ) = 0
mprotect(0x7fac0167d000, 4096, PROT_READ) = 0
mprotect(0x7fac01885000, 4096, PROT_READ) = 0
mprotect(0x7fac01ae7000, 4096, PROT_READ) = 0
mprotect(0x7fac020ba000, 4096, PROT_READ) = 0
mprotect(0x7fac022c3000, 4096, PROT_READ) = 0
mprotect(0x7fac024e8000, 4096, PROT_READ) = 0
mprotect(0x61d000, 4096, PROT_READ)     = 0
mprotect(0x7fac0270d000, 4096, PROT_READ) = 0
munmap(0x7fac026f5000, 93690)           = 0
set_tid_address(0x7fac026f0b10)         = 38725
set_robust_list(0x7fac026f0b20, 24)     = 0
rt_sigaction(SIGRTMIN, {0x7fac0146d820, [], SA_RESTORER|SA_SIGINFO, 0x7fac014765f0}, NULL, 8) = 0
rt_sigaction(SIGRT_1, {0x7fac0146d8b0, [], SA_RESTORER|SA_RESTART|SA_SIGINFO, 0x7fac014765f0}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
statfs("/sys/fs/selinux", {f_type=SELINUX_MAGIC, f_bsize=4096, f_blocks=0, f_bfree=0, f_bavail=0, f_files=0, f_ffree=0, f_fsid={0, 0}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_RELATIME}) = 0
statfs("/sys/fs/selinux", {f_type=SELINUX_MAGIC, f_bsize=4096, f_blocks=0, f_bfree=0, f_bavail=0, f_files=0, f_ffree=0, f_fsid={0, 0}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_RELATIME}) = 0
stat("/sys/fs/selinux", {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
brk(NULL)                               = 0x17bc000
brk(0x17dd000)                          = 0x17dd000
access("/etc/selinux/config", F_OK)     = 0
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=106075056, ...}) = 0
mmap(NULL, 106075056, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fabfaf3d000
close(3)                                = 0
geteuid()                               = 1000
ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
stat("LN_TEST2", 0x7ffdf098e5a0)        = -1 ENOENT (No such file or directory)
lstat("LN_TEST", {st_mode=S_IFLNK|0777, st_size=6, ...}) = 0
lstat("LN_TEST2", 0x7ffdf098e250)       = -1 ENOENT (No such file or directory)
renameat2(AT_FDCWD, "LN_TEST", AT_FDCWD, "LN_TEST2", 0) = 0
lseek(0, 0, SEEK_CUR)                   = -1 ESPIPE (Illegal seek)
close(0)                                = 0
close(1)                                = 0
close(2)                                = 0
exit_group(0)                           = ?
+++ exited with 0 +++
```