I'm installing Debian testing on a SSD, there is a pre-existing EFI ESP partition from windows installation, the disk uses GPT partitioning. Problem is after it finishes installing it won't boot linux or grub. In my motherboard UEFI boot order I see a japenese sign that appeared after the installation, when I try to boot on it it won't do anything. Any idea ?efibootmgr -vroot@ubuntu:~# efibootmgr -vBootCurrent: 000BTimeout: 1 secondsBootOrder: 0002,0006,0007,0008,000A,000B,000C,0000Boot0000* debian    VenHw(99e275e7-75a0-4b37-a2e6-c5385e6c00cb)Boot0002* Windows Boot Manager  HD(2,GPT,b790d826-8e17-4ec7-b89b-12d783ec520e,0xe1800,0x32000)/File(\EFI\MICROSOFT\BOOT\BOOTMGFW.EFI)WINDOWS.........x...B.C.D.O.B.J.E.C.T.=.{.9.d.e.a.8.6.2.c.-.5.c.d.d.-.4.e.7.0.-.a.c.c.1.-.f.3.2.b.3.4.4.d.4.7.9.5.}...9................Boot0006* Hard Drive    BBS(HD,,0x0)..GO..NO..........N.1.-.S.a.m.s.u.n.g. .S.S.D. .9.5.0. .P.R.O. .5.1.2.G.B....................A........................1.N........>.;......N..Gd-.;.A..MQ..L.N.1.-.S.a.m.s.u.n.g. .S.S.D. .9.5.0. .P.R.O. .5.1.2.G.B........BO..NO........o.W.D.C. .W.D.6.0.0.1.F.F.W.X.-.6.8.Z.3.9.N.0....................A...........................>..Gd-.;.A..MQ..L. . . . .W. .-.D.X.W.1.4.7.D.L.5.8.N.5.H........BOBoot0007* CD/DVD Drive  BBS(CDROM,,0x0)..GO..NO........o.A.T.A.P.I. . . .i.H.A.S.1.2.4. . . .E....................A...........................>..Gd-.;.A..MQ..L.5.3.4.2.0.7. .3.L.2.4.8.3.4.0.5.4.9.9.8........BOBoot0008* USB   BBS(USB,,0x0)..GO..NO........i.V.e.r.b.a.t.i.m.S.T.O.R.E. .N. .G.O. .1.1.0.0....................A.............................6..Gd-.;.A..MQ..L.1.3.1.1.0.4.0.0.0.0.0.0.4.3.2.4........BO..NO........}. .M.E.M.U.P. .1...0.0....................A.............................J..Gd-.;.A..MQ..L.0.9.0.2.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.5.4.8........BOBoot000A* UEFI: ATAPI   iHAS124   E PciRoot(0x0)/Pci(0x11,0x4)/Sata(2,65535,0)/CDROM(0,0x33f,0xdffb0)/HD(1,MBR,0x0,0x20,0x7fe0)..BOBoot000B* UEFI: VerbatimSTORE N GO 1100 PciRoot(0x0)/Pci(0x1a,0x0)/USB(1,0)/USB(2,0)/HD(1,MBR,0x0,0x800,0x1dd9000)..BOBoot000C* UEFI:  MEMUP 1.00 PciRoot(0x0)/Pci(0x1d,0x0)/USB(1,0)/USB(5,0)/HD(1,MBR,0x0,0x800,0xeeb800)..BOtree EFI :root@ubuntu:/# mount /dev/nvme0n1p2 /mntroot@ubuntu:/# ls mntEFIroot@ubuntu:/# tree /mnt/mnt EFI     Boot      bootx64.efi     debian      grubx64.efi     Microsoft         Boot          BCD          BCD.LOG          BCD.LOG1          BCD.LOG2          bg-BG           bootmgfw.efi.mui           bootmgr.efi.mui          bootmgfw.efi          bootmgr.efi          BOOTSTAT.DAT          boot.stl          cs-CZ           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          da-DK           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          de-DE           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          el-GR           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          en-GB           bootmgfw.efi.mui           bootmgr.efi.mui          en-US           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          es-ES           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          es-MX           bootmgfw.efi.mui           bootmgr.efi.mui          et-EE           bootmgfw.efi.mui           bootmgr.efi.mui          fi-FI           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          Fonts           chs_boot.ttf           cht_boot.ttf           jpn_boot.ttf           kor_boot.ttf           malgun_boot.ttf           malgunn_boot.ttf           meiryo_boot.ttf           meiryon_boot.ttf           msjh_boot.ttf           msjhn_boot.ttf           msyh_boot.ttf           msyhn_boot.ttf           segmono_boot.ttf           segoen_slboot.ttf           segoe_slboot.ttf           wgl4_boot.ttf          fr-CA           bootmgfw.efi.mui           bootmgr.efi.mui          fr-FR           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          hr-HR           bootmgfw.efi.mui           bootmgr.efi.mui          hu-HU           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          it-IT           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          ja-JP           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          kd_02_10df.dll          kd_02_10ec.dll          kd_02_1137.dll          kd_02_14e4.dll          kd_02_15b3.dll          kd_02_1969.dll          kd_02_19a2.dll          kd_02_8086.dll          kd_07_1415.dll          kd_0C_8086.dll          kdstub.dll          ko-KR           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          lt-LT           bootmgfw.efi.mui           bootmgr.efi.mui          lv-LV           bootmgfw.efi.mui           bootmgr.efi.mui          memtest.efi          nb-NO           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          nl-NL           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          pl-PL           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          pt-BR           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          pt-PT           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          qps-ploc           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          Resources           bootres.dll           fr-FR               bootres.dll.mui          ro-RO           bootmgfw.efi.mui           bootmgr.efi.mui          ru-RU           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          sk-SK           bootmgfw.efi.mui           bootmgr.efi.mui          sl-SI           bootmgfw.efi.mui           bootmgr.efi.mui          sr-Latn-CS           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          sr-Latn-RS           bootmgfw.efi.mui           bootmgr.efi.mui          sv-SE           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          tr-TR           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          uk-UA           bootmgfw.efi.mui           bootmgr.efi.mui          zh-CN           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          zh-HK           bootmgfw.efi.mui           bootmgr.efi.mui           memtest.efi.mui          zh-TW              bootmgfw.efi.mui              bootmgr.efi.mui              memtest.efi.mui         Recovery             BCD             BCD.LOG             BCD.LOG1             BCD.LOG2
Installing Debian but can't boot
debian;boot;grub;uefi
To me, it seems that something went wrong with the installation of GRUB. I would try to create a new firmware boot entry first:efibootmgr -c -d /dev/disk/by-uuid/b790d826-8e17-4ec7-b89b-12d783ec520e -p 2 -l /EFI/debian/grubx64.efi -L Debian(for more information see e.g. https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface#efibootmgr)This will not touch other boot options and can be removed if it didn't work.If this doesn't fix your installation, you can try to re-install GRUB. You can do this by booting a live CD (preferably one which matches your installation) and chroot to your installation. Afterwards you should run grub-install and update-grub (for more information, again, see e.g. https://wiki.archlinux.org/index.php/GRUB#Installation_2; though you probably can't use arch-chroot with a Debian installation).