Voila le retour de strace -fe write=3 efibootmgr :
# strace -fe write=3 efibootmgr --disk /dev/sda --part 1 --create --gpt --label "ubuntu" --loader "\EFI\ubuntu\shimx64.efi"
execve("/bin/efibootmgr", ["efibootmgr", "--disk", "/dev/sda", "--part", "1", "--create", "--gpt", "--label", "ubuntu", "--loader", "\\EFI\\ubuntu\\shimx64.efi"], 0x7fff440748c0 /* 19 vars */) = 0
brk(NULL) = 0x55d0aaacc000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
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=32193, ...}) = 0
mmap(NULL, 32193, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f2e81a69000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/x86_64-linux-gnu/libefivar.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*\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=146504, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2e81a67000
mmap(NULL, 2242368, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f2e81626000
mprotect(0x7f2e81640000, 2093056, PROT_NONE) = 0
mmap(0x7f2e8183f000, 45056, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19000) = 0x7f2e8183f000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/x86_64-linux-gnu/libefiboot.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\36\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=51120, ...}) = 0
mmap(NULL, 2146336, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f2e81419000
mprotect(0x7f2e81425000, 2093056, PROT_NONE) = 0
mmap(0x7f2e81624000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xb000) = 0x7f2e81624000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
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\260\34\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0
mmap(NULL, 4131552, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f2e81028000
mprotect(0x7f2e8120f000, 2097152, PROT_NONE) = 0
mmap(0x7f2e8140f000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f2e8140f000
mmap(0x7f2e81415000, 15072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f2e81415000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
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\0P\16\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=14560, ...}) = 0
mmap(NULL, 2109712, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f2e80e24000
mprotect(0x7f2e80e27000, 2093056, PROT_NONE) = 0
mmap(0x7f2e81026000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7f2e81026000
close(3) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2e81a65000
arch_prctl(ARCH_SET_FS, 0x7f2e81a65b80) = 0
mprotect(0x7f2e8140f000, 16384, PROT_READ) = 0
mprotect(0x7f2e81026000, 4096, PROT_READ) = 0
mprotect(0x7f2e8183f000, 4096, PROT_READ) = 0
mprotect(0x7f2e81624000, 4096, PROT_READ) = 0
mprotect(0x55d0aa235000, 4096, PROT_READ) = 0
mprotect(0x7f2e81a71000, 4096, PROT_READ) = 0
munmap(0x7f2e81a69000, 32193) = 0
access("/sys/firmware/efi/efivars/", F_OK) = 0
statfs("/sys/firmware/efi/efivars/", {f_type=EFIVARFS_MAGIC, f_bsize=4096, f_blocks=0, f_bfree=0, f_bavail=0, f_files=0, f_ffree=0, f_fsid={val=[0, 0]}, f_namelen=255, f_frsize=4096, f_flags=ST_VALID|ST_NOSUID|ST_NODEV|ST_NOEXEC|ST_RELATIME}) = 0
brk(NULL) = 0x55d0aaacc000
brk(0x55d0aaaed000) = 0x55d0aaaed000
openat(AT_FDCWD, "/sys/firmware/efi/efivars/", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
fstat(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
fcntl(3, F_GETFD) = 0x1 (flags FD_CLOEXEC)
fcntl(3, F_SETFD, FD_CLOEXEC) = 0
getdents(3, /* 40 entries */, 32768) = 2776
getdents(3, /* 0 entries */, 32768) = 0
close(3) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0002-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 3
read(3, "\7\0\0\0", 4) = 4
read(3, "\1\0\0\200\\\0E\0F\0I\0 \0N\0e\0t\0w\0o\0r\0k\0 \0001\0"..., 4096) = 126
read(3, "", 3970) = 0
close(3) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0003-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 3
read(3, "\7\0\0\0", 4) = 4
read(3, "\1\0\0\200\\\0E\0F\0I\0 \0N\0e\0t\0w\0o\0r\0k\0 \0002\0"..., 4096) = 126
read(3, "", 3970) = 0
close(3) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0005-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 3
read(3, "\7\0\0\0", 4) = 4
read(3, "\1\0\0\200J\0E\0F\0I\0 \0F\0i\0x\0e\0d\0 \0D\0i\0s\0"..., 4096) = 138
read(3, "", 3958) = 0
close(3) = 0
openat(AT_FDCWD, "/dev/sda", O_RDONLY) = 3
fstat(3, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
readlink("/sys/dev/block/8:0", "../../devices/pci0000:00/0000:00"..., 4096) = 78
openat(AT_FDCWD, "/dev/sda", O_RDONLY) = 4
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 0, SEEK_SET) = 0
read(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\0\0\0\0\0\0\0\0"..., 512) = 512
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 512, SEEK_SET) = 512
read(4, "EFI PART\0\0\1\0\\\0\0\0\351\26\350\241\0\0\0\0\1\0\0\0\0\0\0\0"..., 512) = 512
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 1024, SEEK_SET) = 1024
read(4, "(s*\301\37\370\322\21\272K\0\240\311>\311;\240\271\210\301\210u\214N\242{\310p9eX2"..., 16384) = 16384
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 250059349504, SEEK_SET) = 250059349504
read(4, "EFI PART\0\0\1\0\\\0\0\0\251\344\305~\0\0\0\0oY\34\35\0\0\0\0"..., 512) = 512
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 250059333120, SEEK_SET) = 250059333120
read(4, "(s*\301\37\370\322\21\272K\0\240\311>\311;\240\271\210\301\210u\214N\242{\310p9eX2"..., 16384) = 16384
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 0, SEEK_SET) = 0
read(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\0\0\0\0\0\0\0\0"..., 512) = 512
close(4) = 0
close(3) = 0
openat(AT_FDCWD, "/dev/sda", O_RDONLY) = 3
fstat(3, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
readlink("/sys/dev/block/8:0", "../../devices/pci0000:00/0000:00"..., 4096) = 78
openat(AT_FDCWD, "/dev/sda", O_RDONLY) = 4
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 0, SEEK_SET) = 0
read(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\0\0\0\0\0\0\0\0"..., 512) = 512
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 512, SEEK_SET) = 512
read(4, "EFI PART\0\0\1\0\\\0\0\0\351\26\350\241\0\0\0\0\1\0\0\0\0\0\0\0"..., 512) = 512
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 1024, SEEK_SET) = 1024
read(4, "(s*\301\37\370\322\21\272K\0\240\311>\311;\240\271\210\301\210u\214N\242{\310p9eX2"..., 16384) = 16384
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 250059349504, SEEK_SET) = 250059349504
read(4, "EFI PART\0\0\1\0\\\0\0\0\251\344\305~\0\0\0\0oY\34\35\0\0\0\0"..., 512) = 512
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 250059333120, SEEK_SET) = 250059333120
read(4, "(s*\301\37\370\322\21\272K\0\240\311>\311;\240\271\210\301\210u\214N\242{\310p9eX2"..., 16384) = 16384
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 0, SEEK_SET) = 0
read(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\0\0\0\0\0\0\0\0"..., 512) = 512
close(4) = 0
close(3) = 0
openat(AT_FDCWD, "/dev/sda", O_RDONLY) = 3
fstat(3, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
readlink("/sys/dev/block/8:0", "../../devices/pci0000:00/0000:00"..., 4096) = 78
openat(AT_FDCWD, "/dev/sda", O_RDONLY) = 4
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 0, SEEK_SET) = 0
read(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\0\0\0\0\0\0\0\0"..., 512) = 512
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 512, SEEK_SET) = 512
read(4, "EFI PART\0\0\1\0\\\0\0\0\351\26\350\241\0\0\0\0\1\0\0\0\0\0\0\0"..., 512) = 512
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 1024, SEEK_SET) = 1024
read(4, "(s*\301\37\370\322\21\272K\0\240\311>\311;\240\271\210\301\210u\214N\242{\310p9eX2"..., 16384) = 16384
fstat(4, {st_mode=S_IFBLK|0660, st_rdev=makedev(8, 0), ...}) = 0
uname({sysname="Linux", nodename="carte-fh", ...}) = 0
ioctl(4, BLKGETSIZE64, [250059350016]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 250059349504, SEEK_SET) = 250059349504
read(4, "EFI PART\0\0\1\0\\\0\0\0\251\344\305~\0\0\0\0oY\34\35\0\0\0\0"..., 512) = 512
ioctl(4, BLKSSZGET, [512]) = 0
brk(0x55d0aab0e000) = 0x55d0aab0e000
lseek(4, 250059333120, SEEK_SET) = 250059333120
read(4, "(s*\301\37\370\322\21\272K\0\240\311>\311;\240\271\210\301\210u\214N\242{\310p9eX2"..., 16384) = 16384
ioctl(4, BLKSSZGET, [512]) = 0
lseek(4, 0, SEEK_SET) = 0
read(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\0\0\0\0\0\0\0\0"..., 512) = 512
close(4) = 0
close(3) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0000-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_WRONLY|O_CREAT|O_EXCL, 0644) = 3
ioctl(3, FS_IOC_GETFLAGS, 0x7ffe851f4b34) = 0
write(3, "\7\0\0\0\1\0\0\0b\0u\0b\0u\0n\0t\0u\0\0\0\4\1*\0\1\0\0\0"..., 122) = -1 EINVAL (Invalid argument)
ioctl(3, FS_IOC_GETFLAGS, 0x7ffe851f4b34) = 0
unlink("/sys/firmware/efi/efivars/Boot0000-8be4df61-93ca-11d2-aa0d-00e098032b8c") = 0
close(3) = 0
write(2, "Could not prepare Boot variable", 31Could not prepare Boot variable) = 31
write(2, ": Invalid argument\n", 19: Invalid argument
) = 19
exit_group(5) = ?
+++ exited with 5 +++