This side describes how to create a USB stick that can boot multiple operating systems. Additionally it should work for (U)EFI and legacy BIOS systems.
First let’s state: It works.
But there could be a problem supporting legacy BIOS systems and use big size USB sticks. So, it is not really a problem, but you need to consider it by the design of the partition layout. To summarize it shortly: The data that could be accessed by legacy BIOS on USB stick is limited by their size. I run into the problem that the BIOS of some of my machines cannot access data that is stored above the 128 GiB / 137 GB limit.
Some further details could be found here:
This could be worked around to place all files that needs to be accessed on bootup initially are places below the 128 GiB limit. For Linux systems this would be the kernel and the initramfs / initrd. All other files from root filesystem will be accessed by the kernel driver and so the limit does not exist anymore.
Personally I would consider what you want to achieve. If you want to create an USB stick with multiple Linux systems using separate boot partitions could increase the initial setup. But it is all doable without big headache.
As written in the first link above there could be other limits too, if you use very old machines, but I did not run into yet.
For further information about the BIOS Boot Partition have a look at BIOS boot partition (Wikipedia en) especially on the image.
| Partition | Use Case | Size | Partition Type | Name |
|---|---|---|---|---|
/dev/sdb1 |
EFI System Partition | +2G | ef00 | EFI_UMB |
/dev/sdb2 |
BIOS Boot Partition | +100M | ef02 | BIOSBOOT_UMB |
/dev/sdb3 |
boot directory of all linux systems | +8G | 8300 | LINBOOT_UMB |
/dev/sdb4 |
Windows Image 1 | +10G | 0700 | WIN1_UMB |
/dev/sdb5 |
Windows Image 2 | +10G | 0700 | WIN2_UMB |
/dev/sdb6 |
remaining stuff of all linux systems | remaining | 8300 | LIN_UMB |
| Partition | Use Case | Size | Partition Type | Name |
|---|---|---|---|---|
/dev/sdb1 |
EFI System Partition | +2G | ef00 | EFI_USBLIN |
/dev/sdb2 |
BIOS Boot Partition | +100M | ef02 | BIOSBOOT_USBLIN |
/dev/sdb3 |
Linux etc. | remaining | 8300 | BTRFS_USBLIN |
# as root
gdisk /dev/sdb
GPT fdisk (gdisk) version 1.0.8
Partition table scan:
MBR: protective
BSD: not present
APM: not present
GPT: present
Found valid GPT with protective MBR; using GPT.
Command (? for help): o
This option deletes all partitions and creates a new protective MBR.
Proceed? (Y/N): Y
Command (? for help): n
Partition number (1-128, default 1):
First sector (34-500170718, default = 2048) or {+-}size{KMGTP}:
Last sector (2048-500170718, default = 500170718) or {+-}size{KMGTP}: +2G
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): ef00
Changed type of partition to 'EFI system partition'
Command (? for help): n
Partition number (2-128, default 2):
First sector (34-500170718, default = 4196352) or {+-}size{KMGTP}:
Last sector (4196352-500170718, default = 500170718) or {+-}size{KMGTP}: +100M
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): ef02
Changed type of partition to 'BIOS boot partition'
Command (? for help): n
Partition number (3-128, default 3):
First sector (34-500170718, default = 4401152) or {+-}size{KMGTP}:
Last sector (4401152-500170718, default = 500170718) or {+-}size{KMGTP}:
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): 8300
Changed type of partition to 'Linux filesystem'
Command (? for help): c
Partition number (1-3): 1
Enter name: EFI_USBLIN
Command (? for help): c
Partition number (1-3): 2
Enter name: BIOSBOOT_USBLIN
Command (? for help): c
Partition number (1-3): 3
Enter name: BTRFS_USBLIN
Command (? for help): wq
Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!
Do you want to proceed? (Y/N): Y
OK; writing new GUID partition table (GPT) to /dev/sdb.
The operation has completed successfully.
Unplug and plug in the USB stick.
mkfs.vfat -n EFI_USBLIN /dev/sdb1
mkfs.btrfs -L BTRFS_USBLIN /dev/sdb3
blkid /dev/sdb*
/dev/sdb: PTUUID="832d97be-48bd-4c42-866e-929e88b2ee90" PTTYPE="gpt"
/dev/sdb1: LABEL_FATBOOT="EFI_USBLIN" LABEL="EFI_USBLIN" UUID="6641-AD18" BLOCK_SIZE="512" TYPE="vfat" PARTLABEL="EFI_USBLIN" PARTUUID="ca5a6790-1e89-4ef3-a5e9-cb8c18aa96f0"
/dev/sdb2: PARTLABEL="BIOSBOOT_USBLIN" PARTUUID="946032eb-4033-474a-8a64-0fcdef93b510"
/dev/sdb3: LABEL="BTRFS_USBLIN" UUID="c40a464a-f21a-48af-b655-b1e75571788f" UUID_SUB="2c90051d-92cf-468d-ba3d-fe784e216bdb" BLOCK_SIZE="4096" TYPE="btrfs" PARTLABEL="BTRFS_USBLIN" PARTUUID="14062ad2-9bf1-4d2e-b33f-c4962961d813"
gdisk /dev/sdb
GPT fdisk (gdisk) version 1.0.8
Partition table scan:
MBR: MBR only
BSD: not present
APM: not present
GPT: not present
***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format
in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by
typing 'q' if you don't want to convert your MBR partitions
to GPT format!
***************************************************************
Warning! Secondary partition table overlaps the last partition by
33 blocks!
You will need to delete this partition or resize it in another utility.
Command (? for help): o
This option deletes all partitions and creates a new protective MBR.
Proceed? (Y/N): Y
Command (? for help): n
Partition number (1-128, default 1):
First sector (34-500170718, default = 2048) or {+-}size{KMGTP}:
Last sector (2048-500170718, default = 500170718) or {+-}size{KMGTP}: +2G
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): ef00
Changed type of partition to 'EFI system partition'
Command (? for help): n
Partition number (2-128, default 2):
First sector (34-500170718, default = 4196352) or {+-}size{KMGTP}:
Last sector (4196352-500170718, default = 500170718) or {+-}size{KMGTP}: +32G
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): 8200
Changed type of partition to 'Linux swap'
Command (? for help): n
Partition number (3-128, default 3):
First sector (34-500170718, default = 71305216) or {+-}size{KMGTP}:
Last sector (71305216-500170718, default = 500170718) or {+-}size{KMGTP}:
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300):
Changed type of partition to 'Linux filesystem'
Command (? for help): c
Partition number (1-3): 1
Enter name: EFI_USBLIN
Command (? for help): c
Partition number (1-3): 2
Enter name: SWAP_USBLIN
Command (? for help): c
Partition number (1-3): 3
Enter name: BTRFS_USBLIN
Command (? for help): wq
Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!
Do you want to proceed? (Y/N): Y
OK; writing new GUID partition table (GPT) to /dev/sdb.
The operation has completed successfully.
mkfs.vfat -n EFI_USBLIN /dev/sdb1
mkswap -L SWAP_USBLIN /dev/sdb2
mkfs.btrfs -L BTRFS_USBLIN /dev/sdb3
blkid /dev/sdb*
/dev/sdb: PTUUID="192efcf3-550f-48b3-b997-3f6298eb9900" PTTYPE="gpt"
/dev/sdb1: LABEL_FATBOOT="EFI_USBLIN" LABEL="EFI_USBLIN" UUID="BD6C-E793" BLOCK_SIZE="512" TYPE="vfat" PARTLABEL="EFI_USBLIN" PARTUUID="208d55b6-112c-4bd9-a0fd-5cb309b72fd7"
/dev/sdb2: LABEL="SWAP_USBLIN" UUID="7ee2e029-181d-4fe6-b90f-ffcfc0a19640" TYPE="swap" PARTLABEL="SWAP_USBLIN" PARTUUID="e5f81256-52fd-4bc9-a0e6-ae22666753e3"
/dev/sdb3: LABEL="BTRFS_USBLIN" UUID="0f7a4702-0202-4e56-b3ba-e03c180ea621" UUID_SUB="c01dfff8-89f1-4d04-b3a7-0e304e93f2d7" BLOCK_SIZE="4096" TYPE="btrfs" PARTLABEL="BTRFS_USBLIN" PARTUUID="47ba980c-87d0-4e6c-9214-7a51f036a62d"
export MP_BTRFS_USBLIN=$(mktemp -d)
mount /dev/disk/by-label/BTRFS_USBLIN "${MP_BTRFS_USBLIN}"
btrfs subvolume create "${MP_BTRFS_USBLIN}"/ubuntu.focal
btrfs subvolume create "${MP_BTRFS_USBLIN}"/archlinux
umount "${MP_BTRFS_USBLIN}"
rmdir "${MP_BTRFS_USBLIN}"
unset MP_BTRFS_USBLIN
mkdir -p /mnt/usblin_ubuntu_focal
mount /dev/disk/by-label/BTRFS_USBLIN -o subvol=ubuntu.focal /mnt/usblin_ubuntu_focal
mkdir -p /mnt/usblin_archlinux
mount /dev/disk/by-label/BTRFS_USBLIN -o subvol=archlinux /mnt/usblin_archlinux
# BEG: bootstrap - simple
debootstrap --arch=amd64 focal /mnt/usblin_ubuntu_focal
tar xzf /tmp/archlinux-bootstrap-2022.01.01-x86_64.tar.gz --numeric-owner --strip-components=1 -C /mnt/usblin_archlinux/
# END: bootstrap - simple
# TODO: setup bootstrapped simple systems (see links)
umount /mnt/usblin_archlinux
umount /mnt/usblin_ubuntu_focal
gdisk partition table
Number Start (sector) End (sector) Size Code Name
1 2048 4196351 2.0 GiB EF00 EFI_PLSDEP1
2 4196352 1819281407 865.5 GiB 8300 MAIN_PLSDEP1
3 1819281408 1953459583 64.0 GiB 8300 SWAP_PLSDEP1
EFI same as examples above.
MAIN_PLSDEP1 will be used for encrypted rootfs (+ boot)
cryptsetup luksFormat --type luks1 /dev/sda2
cryptsetup open /dev/sda2 MAIN_PLSDEP1
mkfs.btrfs -L BTRFS_PLSDEP1 /dev/mapper/MAIN_PLSDEP1
mkdir /tmp/btrfs; mount /dev/mapper/MAIN_PLSDEP1 /tmp/btrfs
cd /tmp/btrfs
btrfs subvolume create machines
btrfs subvolume create machines/ubuntu.focal
cd
umount /tmp/btrfs
# bootstrap
mount -t btrfs -o subvol=/machines/ubuntu.focal /dev/mapper/MAIN_PLSDEP1 /tmp/ubuntu.focal/
debootstrap focal /tmp/ubuntu.focal/
# follow separate guide
# before install "linux-image-generic"
apt install cryptsetup-initramfs
# Now /etc/crypttab should be edited - for this guide we fix it later
/efi/EFI/ubuntu/grub/grub.cfg
insmod part_gpt
insmod btrfs
insmod gzio
insmod gettext
insmod all_video
insmod gfxterm
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
set default=0
#set MPUUID="6b9599f3-3588-45d3-a4ca-d7f5f3fdb34d"
#search --no-floppy --fs-uuid --set=root $MPUUID
set CRYPTUUID="c65b3f7aea68478d896ae5cc706eaddb"
set MPUUID="715e05a1-0172-4fe3-835e-4fe8c5904139"
insmod luks
cryptomount -u $CRYPTUUID
search --no-floppy --fs-uuid --set=root $MPUUID
menuentry 'Ubuntu 20.04 - Focal Fossa' {
set MPSUBVOL="/machines/ubuntu.focal"
#linux /$MPSUBVOL/boot/vmlinuz rootwait root=UUID=$MPUUID rootflags=subvol=$MPSUBVOL rw
linux /$MPSUBVOL/boot/vmlinuz cryptdevice=UUID=$MPUUIDD:main rootwait root=/dev/mapper/main rootflags=subvol=$MPSUBVOL rw
initrd /$MPSUBVOL/boot/initrd.img
}
menuentry 'Ubuntu 22.04 - Jammy Jellyfish' {
set MPSUBVOL="/machines/ubuntu.jammy"
linux /$MPSUBVOL/boot/vmlinuz rootwait root=UUID=$MPUUID rootflags=subvol=$MPSUBVOL rw
initrd /$MPSUBVOL/boot/initrd.img
}
As commented above crypttab has not been edited in front of initramfs creation, so you will end up in the initramfs shell. Fix it and continue:
cryptsetup open /dev/sda2 main
exit
After the start succeeded fix the crypttab in the initramfs.
/etc/crypttab
# <target name> <source device> <key file> <options>
main UUID="c65b3f7a-ea68-478d-896a-e5cc706eaddb" none luks,discard
update-initramfs -u -k all
Number Start (sector) End (sector) Size Code Name
1 2048 4196351 2.0 GiB EF00 EFI_PLSDEP1
2 4196352 20973567 8.0 GiB 8300 BOOT_PLSDEP1
3 20973568 1819281407 857.5 GiB 8300 MAIN_PLSDEP1
4 1819281408 1953459583 64.0 GiB 8300 SWAP_PLSDEP1
mkfs.btrfs -L BOOT_PLSDEP1 /dev/sdb2
cryptsetup luksFormat --type luks2 /dev/sdb3
cryptsetup open /dev/sdb3 MAIN_PLSDEP1
mkfs.btrfs -L MAIN_PLSDEP1 /dev/mapper/MAIN_PLSDEP1
mkdir -p /tmp/btrfs; mount /dev/mapper/MAIN_PLSDEP1 /tmp/btrfs
cd /tmp/btrfs
btrfs subvolume create machines
btrfs subvolume create machines/ubuntu.focal
cd
umount /tmp/btrfs
mkdir -p /tmp/btrfs; mount /dev/sdb2 /tmp/btrfs
cd /tmp/btrfs
btrfs subvolume create ubuntu.focal
cd
umount /tmp/btrfs
/dev/sdb: PTUUID="928eac5b-7f03-498f-b835-69e49e038424" PTTYPE="gpt"
/dev/sdb1: LABEL_FATBOOT="EFI_PLSDEP1" LABEL="EFI_PLSDEP1" UUID="266C-436B" BLOCK_SIZE="512" TYPE="vfat" PARTLABEL="EFI_PLSDEP1" PARTUUID="23e4eeba-96aa-479a-b3f8-63553cfdfc30"
/dev/sdb2: LABEL="BOOT_PLSDEP1" UUID="d388dd11-f7bb-4a0c-b93f-5950ad9fc276" UUID_SUB="d6ddc6cb-c98c-440e-bb5d-1b490c24ba64" BLOCK_SIZE="4096" TYPE="btrfs" PARTLABEL="BOOT_PLSDEP1" PARTUUID="6449fe37-f31e-4f3d-a9e0-a3530e47da50"
/dev/sdb3: UUID="ff4c7b9b-de95-4a6f-a6f9-ce35fc133191" TYPE="crypto_LUKS" PARTLABEL="MAIN_PLSDEP1" PARTUUID="60f12f6d-52c8-4d78-863a-17c2b5c47182"
/dev/sdb4: PARTLABEL="SWAP_PLSDEP1" PARTUUID="ee7f066a-04cc-4674-afc0-d7d59f48694a"
/dev/mapper/MAIN_PLSDEP1: LABEL="MAIN_PLSDEP1" UUID="7924d6bd-bdb1-461a-bb0e-e3f14e5e2b18" UUID_SUB="a542981e-7b80-40b5-9ea4-4b702815f961" BLOCK_SIZE="4096" TYPE="btrfs"
# bootstrap
mkdir -p /tmp/ubuntu.focal
mount -t btrfs -o subvol=/machines/ubuntu.focal /dev/mapper/MAIN_PLSDEP1 /tmp/ubuntu.focal/
mkdir -p /tmp/ubuntu.focal/boot
mount -t btrfs -o subvol=/ubuntu.focal /dev/sdb2 /tmp/ubuntu.focal/boot
debootstrap focal /tmp/ubuntu.focal/
# follow separate guide
# BEG: before install "linux-image-generic"
apt install cryptsetup-initramfs
cat <<EOF >/etc/crypttab
# <target name> <source device> <key file> <options>
main UUID="ff4c7b9b-de95-4a6f-a6f9-ce35fc133191" none luks,discard
EOF
# END: before install "linux-image-generic"
cat <<EOF >/etc/fstab
UUID=d388dd11-f7bb-4a0c-b93f-5950ad9fc276 /boot btrfs subvol=/ubuntu.focal 0 0
UUID=266C-436B /efi vfat noauto 0 0
EOF
/efi/EFI/ubuntu/grub/grub.cfg
insmod part_gpt
insmod btrfs
insmod gzio
insmod gettext
insmod all_video
insmod gfxterm
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
set default=0
menuentry 'Ubuntu 20.04 - Focal Fossa' {
set UUID_MAIN_ENC="ff4c7b9b-de95-4a6f-a6f9-ce35fc133191"
set UUID_BOOT="d388dd11-f7bb-4a0c-b93f-5950ad9fc276"
search --no-floppy --fs-uuid --set=root $UUID_BOOT
set BOOT_SUBVOL="/ubuntu.focal"
set MAIN_SUBVOL="/machines/ubuntu.focal"
linux $BOOT_SUBVOL/vmlinuz cryptdevice=UUID=$UUID_MAIN_ENC:main rootwait root=/dev/mapper/main rootflags=subvol=$MAIN_SUBVOL rw
initrd $BOOT_SUBVOL/initrd.img
}
On the first initramfs generation crypttab etc. has not been setup correctly. You will end up in the initramfs shell. Fix it and continue:
cryptsetup open /dev/sda2 main
exit
After the start succeeded regenerate the initramfs.
update-initramfs -u -k all
Bootstrap a Linux System to a subvolume of “BTRFS_USBLIN”.
mkdir /tmp/3; mount /dev/sdb3 /tmp/3
btrfs subvolume create /tmp/3/ubuntu.focal
debootstrap --arch=amd64 focal /tmp/3/ubuntu.focal/
For further instructions see e.g. bootstrap
umount /tmp/3
We decide to use Grub as we can use one configuration for:
We apply the steps in an Arch Linux system as we can install ONE grub for all targets. On Debian / Ubuntu you need to install different packages (and remove them again, as only one can be installed in parallel).
So, let’s assume you have a running Arch Linux system (or chroot setup with all relevant dev, proc, sys etc. stuff).
Install Grub
pacman -S grub
Mount ESP
mkdir -p /efi
mount /dev/disk/by-label/EFI_USBLIN /efi
mkdir -p /efi/EFI/BOOT/
grub-install --target=i386-pc --boot-directory=/efi/boot /dev/sdb
grub-install --target=i386-efi --boot-directory=/efi/boot --efi-directory=/efi --bootloader-id=grub --no-nvram
mkdir -p /efi/EFI/BOOT/
cp /efi/EFI/grub/grubia32.efi /efi/EFI/BOOT/BOOTIA32.EFI
grub-install --target=x86_64-efi --boot-directory=/efi/boot --efi-directory=/efi --bootloader-id=grub --no-nvram
mkdir -p /efi/EFI/BOOT/
cp /efi/EFI/grub/grubx64.efi /efi/EFI/BOOT/BOOTX64.EFI
Now edit the configuration file /efi/boot/grub/grub.cfg
search.fs_uuid 6641-AD18 root hd1,gpt1
set prefix=($root)'/boot/grub'
configfile $prefix/grub-manual.cfg
and file /efi/boot/grub/grub-manual.cfg:
insmod part_gpt
insmod btrfs
insmod gzio
insmod gettext
insmod all_video
insmod gfxterm
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
set default=0
set MPUUID="c40a464a-f21a-48af-b655-b1e75571788f"
search --no-floppy --fs-uuid --set=root $MPUUID
menuentry 'Ubuntu Focal' {
set MPSUBVOL="ubuntu.focal"
linux /$MPSUBVOL/boot/vmlinuz rootwait root=UUID=$MPUUID rootflags=subvol=$MPSUBVOL rw
initrd /$MPSUBVOL/boot/initrd.img
}
menuentry 'Arch Linux' {
set MPSUBVOL="archlinux"
linux /$MPSUBVOL/boot/vmlinuz-linux rootwait root=UUID=$MPUUID rootflags=subvol=$MPSUBVOL rw
initrd /$MPSUBVOL/boot/initramfs-linux.img
}
Signed bootloaders will not be modified anymore, so for grub the configuration location is already fix in the signed efi file. Distributions normally use the distribution name (e.g. Ubuntu is using “ubuntu”). So ensure to use correct “bootloader-id” because in this location the grub.cfg will be looked for.
It seems like the signatures of shim signed + grub signed + kernel signed on Ubuntu are distribution dependent. At least shim + grub of Ubuntu Jammy cannot load a kernel of Ubuntu Focal. Because if this it make sense to place the grub directory inside the specific efi directory, so you can move the directories around if you want to use another one…
export MPBS="/mnt/usblin_ubuntu_focal"
mount /dev/disk/by-label/BTRFS_USBLIN -o subvol=ubuntu.focal /mnt/usblin_ubuntu_focal
mount -t proc /proc "${MPBS}/proc"
mount --rbind /sys "${MPBS}/sys"
mount --rbind /run "${MPBS}/run"
mount --rbind /dev "${MPBS}/dev"
chroot "${MPBS}"
# BEG: inside chroot
apt install shim-signed grub-efi-amd64-signed
mkdir -p /efi
mount /dev/disk/by-label/EFI_USBLIN /efi
grub-install --uefi-secure-boot --target=x86_64-efi --boot-directory=/efi/EFI/ubuntu --efi-directory=/efi --bootloader-id=ubuntu --no-nvram
####rm ./EFI/BOOT/fbx64.efi
##cp ./EFI/ubuntu/grubx64.efi ./EFI/BOOT
vim ./EFI/ubuntu/grub/grub.cfg
# END: inside chroot
umount "${MPBS}/"*
umount "${MPBS}"
unset MPBS
We prefer using grub as grub can also be used for non UEFI systems and we can load the kernel from BTRFS filesystem.
mkdir /tmp/1; mount /dev/sdb1 /tmp/1
bootctl install --esp-path=/tmp/1 --no-variables --make-machine-id-directory=no
Created "/tmp/1/EFI".
Created "/tmp/1/EFI/systemd".
Created "/tmp/1/EFI/BOOT".
Created "/tmp/1/loader".
Created "/tmp/1/loader/entries".
Created "/tmp/1/EFI/Linux".
Copied "/usr/lib/systemd/boot/efi/systemd-bootx64.efi" to "/tmp/1/EFI/systemd/systemd-bootx64.efi".
Copied "/usr/lib/systemd/boot/efi/systemd-bootx64.efi" to "/tmp/1/EFI/BOOT/BOOTX64.EFI".
Random seed file /tmp/1/loader/random-seed successfully written (512 bytes).
umount /tmp/1
mkdir /tmp/1; mount /dev/sdb3 /tmp/1
mkdir /tmp/3; mount /dev/sdb3 /tmp/3
mkdir -p /tmp/1/boot/ubuntu.focal/
cp /tmp/3/ubuntu.focal/boot/vmlinuz-5.4.0-26-generic /tmp/1/boot/ubuntu.focal/vmlinuz
cp /tmp/3/ubuntu.focal/boot/initrd.img /tmp/1/boot/ubuntu.focal/initrd.img
cat >/tmp/1/loader/entries/ubuntu.focal.conf <<EOF
title Ubuntu Focal
linux /boot/ubuntu.focal/vmlinuz
initrd /boot/ubuntu.focal/initrd.img
options rootwait root=UUID=c40a464a-f21a-48af-b655-b1e75571788f rootflags=subvol=ubuntu.focal rw
EOF
cat >/tmp/1/loader/loader.conf <<EOF
timeout menu-force
EOF
umount /tmp/3
umount /tmp/1