root@OpenWrt:/etc# strace -ff mv firewall.user fw.user
execve("/bin/mv", ["mv", "firewall.user", "fw.user"], [/* 8 vars */]) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x77d67000
stat("/etc/ld.so.cache", 0x7fd098f0)    = -1 ENOENT (No such file or directory)
open("/lib/libcrypt.so.0", O_RDONLY)    = 3
fstat(3, {st_mode=S_IFREG|0755, st_size=9712, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x77d66000
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\10\0\0\0\1\0\0\4\0\0\0\0004"..., 4096) = 4096
mmap(NULL, 147456, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x77d2e000
mmap(0x77d2e000, 9644, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x77d2e000
mmap(0x77d40000, 1520, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x2000) = 0x77d40000
mmap(0x77d41000, 67696, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x77d41000
close(3)                                = 0
munmap(0x77d66000, 4096)                = 0
open("/lib/libm.so.0", O_RDONLY)        = 3
fstat(3, {st_mode=S_IFREG|0755, st_size=89392, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x77d66000
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\10\0\0\0\1\0\0\22\360\0\0\0004"..., 4096) = 4096
mmap(NULL, 155648, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x77d08000
mmap(0x77d08000, 88904, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x77d08000
mmap(0x77d2d000, 3376, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x15000) = 0x77d2d000
close(3)                                = 0
munmap(0x77d66000, 4096)                = 0
open("/lib/libgcc_s.so.1", O_RDONLY)    = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=78648, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x77d66000
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\10\0\0\0\1\0\0006\340\0\0\0004"..., 4096) = 4096
mmap(NULL, 147456, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x77ce4000
mmap(0x77ce4000, 78268, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x77ce4000
mmap(0x77d07000, 824, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x13000) = 0x77d07000
close(3)                                = 0
munmap(0x77d66000, 4096)                = 0
open("/lib/libc.so.0", O_RDONLY)        = 3
fstat(3, {st_mode=S_IFREG|0755, st_size=359596, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x77d66000
read(3, "\177ELF\1\2\1\0\0\0\0\0\0\0\0\0\0\3\0\10\0\0\0\1\0\0\235\0\0\0\0004"..., 4096) = 4096
mmap(NULL, 446464, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x77c77000
mmap(0x77c77000, 352496, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x77c77000
mmap(0x77cdd000, 7340, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x56000) = 0x77cdd000
mmap(0x77cdf000, 17508, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x77cdf000
close(3)                                = 0
munmap(0x77d66000, 4096)                = 0
open("/lib/libc.so.0", O_RDONLY)        = 3
fstat(3, {st_mode=S_IFREG|0755, st_size=359596, ...}) = 0
close(3)                                = 0
open("/lib/libc.so.0", O_RDONLY)        = 3
fstat(3, {st_mode=S_IFREG|0755, st_size=359596, ...}) = 0
close(3)                                = 0
open("/lib/libc.so.0", O_RDONLY)        = 3
fstat(3, {st_mode=S_IFREG|0755, st_size=359596, ...}) = 0
close(3)                                = 0
stat("/lib/ld-uClibc.so.0", {st_mode=S_IFREG|0755, st_size=28972, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x77d66000
set_thread_area(0x77d6d440)             = 0
mprotect(0x77cdd000, 4096, PROT_READ)   = 0
mprotect(0x77d68000, 4096, PROT_READ)   = 0
ioctl(0, TIOCNXCL, {B38400 opost isig icanon echo ...}) = 0
ioctl(1, TIOCNXCL, {B38400 opost isig icanon echo ...}) = 0
getuid()                                = 0
stat64("fw.user", 0x7fd09908)           = -1 ENOENT (No such file or directory)
rename("firewall.user", "fw.user")      = -1 EINVAL (Invalid argument)
brk(0)                                  = 0x87a000
brk(0x87b000)                           = 0x87b000
brk(0x87c000)                           = 0x87c000
write(2, "mv: can't rename 'firewall.user'"..., 51mv: can't rename 'firewall.user': Invalid argument
) = 51
exit_group(1)                           = ?
+++ exited with 1 +++