tom@ubuntu:~$ strace sudo -k
execve("/usr/bin/sudo", ["sudo", "-k"], [/* 39 vars */]) = 0
brk(0)                                  = 0xb5c000
fcntl(0, F_GETFD)                       = 0
fcntl(1, F_GETFD)                       = 0
fcntl(2, F_GETFD)                       = 0
access("/etc/suid-debug", F_OK)         = -1 ENOENT (No such file or directory)
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1c993e0000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=59679, ...}) = 0
mmap(NULL, 59679, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f1c993d1000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libutil.so.1", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\20\16\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=10640, ...}) = 0
mmap(NULL, 2105608, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1c98fbf000
mprotect(0x7f1c98fc1000, 2093056, PROT_NONE) = 0
mmap(0x7f1c991c0000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1000) = 0x7f1c991c0000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libpam.so.0", O_RDONLY) = 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=55848, ...}) = 0
mmap(NULL, 2150944, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1c98db1000
mprotect(0x7f1c98dbd000, 2097152, PROT_NONE) = 0
mmap(0x7f1c98fbd000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xc000) = 0x7f1c98fbd000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0 \24\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1677624, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1c993d0000
mmap(NULL, 3793768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1c98a12000
mprotect(0x7f1c98ba7000, 2093056, PROT_NONE) = 0
mmap(0x7f1c98da6000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x194000) = 0x7f1c98da6000
mmap(0x7f1c98dab000, 21352, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1c98dab000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libdl.so.2", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\340\r\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=14768, ...}) = 0
mmap(NULL, 2109704, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1c9880e000
mprotect(0x7f1c98810000, 2097152, PROT_NONE) = 0
mmap(0x7f1c98a10000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f1c98a10000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1c993cf000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1c993cd000
arch_prctl(ARCH_SET_FS, 0x7f1c993cd720) = 0
mprotect(0x7f1c98a10000, 4096, PROT_READ) = 0
mprotect(0x7f1c98da6000, 16384, PROT_READ) = 0
mprotect(0x7f1c98fbd000, 4096, PROT_READ) = 0
mprotect(0x7f1c991c0000, 4096, PROT_READ) = 0
mprotect(0x626000, 4096, PROT_do READ)     = 0
mprotect(0x7f1c993e2000, 4096, PROT_READ) = 0
munmap(0x7f1c993d1000, 59679)           = 0
brk(0)                                  = 0xb5c000
brk(0xb7d000)                           = 0xb7d000
open("/usr/lib/locale/locale-archive", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=1607648, ...}) = 0
mmap(NULL, 1607648, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f1c99244000
close(3)                                = 0
geteuid()                               = 1000
write(2, "sudo", 4sudo)                     = 4
write(2, ": ", 2: )                       = 2
write(2, "must be setuid root", 19must be setuid root)     = 19
write(2, "\n", 1
)                       = 1
exit_group(1)                           = ?
tom@ubuntu:~$