This script automates the setup of a Btrfs-based filesystem layout on Ubuntu. It mounts the root Btrfs partition, creates a predefined set of subvolumes (including user-specific ones like ~/bin and ~/dev), ensures mount points exist, and sets appropriate ownership for user directories. It's designed to be used after a fresh installation, restori…

gen-fstab-plus.sh

#!/bin/bash
# set -x
# This script automates the setup of a Btrfs-based filesystem layout on Ubuntu.
# It mounts the root Btrfs partition, creates a predefined set of subvolumes
# (including user-specific ones like ~/bin and ~/dev), ensures mount points
# exist, and sets appropriate ownership for user directories.
#
# It's designed to be used after a fresh installation. It restores filesystem
# info from /etc/fstab.bak and prepares the system for a clean and reproducible
# /etc/fstab regeneration.
#
# IMPORTANT:
# If you plan to mount SMB/CIFS volumes, make sure to install the 'cifs-utils' package.
# On Debian/Ubuntu systems, you can install it with:
#   sudo apt-get install cifs-utils
#
# generated by afreisinger/gen-fstab-plus.sh https://gist.github.com/afreisinger/ab82936d5434b83503562ed66534373e

# OPTIONAL: enable or disable bind mounts from /data
ENABLE_BIND_MOUNTS=true  # Set to false to skip bind mounts

# OPTIONAL: enable CIFS mount (e.g. for backups)
ENABLE_CIFS_MOUNT=true
CIFS_SOURCE="//192.168.1.20/bups"
CIFS_TARGET="/mnt/bups"
CIFS_CREDENTIALS="/etc/cifs_credentials"
CIFS_UID=1000
CIFS_GID=1000
CIFS_OPTIONS="credentials=$CIFS_CREDENTIALS,rw,noperm,iocharset=utf8,uid=$CIFS_UID,gid=$CIFS_GID,vers=3.0"

LOGFILE="/var/log/btrfs_setup.log"

if [ "$EUID" -ne 0 ]; then
    echo "Please run as root"
    exit 1
fi

log() {
    local msg="$1"
    local timestamp
    timestamp=$(date "+%Y-%m-%d %H:%M:%S")
    echo "[$timestamp] $msg" | tee -a "$LOGFILE"
}

verify_mounts() {
    log "Verifying mounted subvolumes..."
    local all_mounted=true

    for subvol in "${!subvolumes[@]}"; do
        mount_point="${subvolumes[$subvol]}"
        if mountpoint -q "$mount_point"; then
            log "$mount_point is mounted."
        else
            log "$mount_point is NOT mounted."
            all_mounted=false
        fi
    done
    if $all_mounted; then
        log "All configured subvolumes are mounted correctly."
    else
        log "One or more subvolumes are not mounted."
    fi
}


log "Script started."

# Prompt for username (defaults to current user)
read -p "Enter your username (default: $USER): " inputUser
USER="${inputUser:-$USER}"

defaultBtrfsOptions="ssd,noatime,space_cache=v2,compress=lzo"

declare -A btrfsOptionsBySubvol=(
    [@]="$defaultBtrfsOptions"
    [@snapshots]="$defaultBtrfsOptions"
    [@cache]="ssd,noatime,space_cache=v2,compress=no"
    #[@log]="ssd,noatime,space_cache=v2,nodatacow,compress=no"
    #[@tmp]="ssd,noatime,space_cache=v2"
)


# Check that backup fstab exists
if [ ! -f /etc/fstab.bak ]; then
    log "Error: /etc/fstab.bak not found. Aborting."
    exit 1
fi

# Parse filesystems from backup
getBootFS=$(awk '$3 == "vfat" {print $1}' /etc/fstab.bak)
getRootFS=$(awk '$3 == "btrfs" {print $1; exit}' /etc/fstab.bak)
getSwapFS=$(lsblk -ln -o NAME,FSTYPE,UUID | awk '$2 == "swap" {print "UUID=" $3}') 

# Check that Btrfs root filesystem found 
if [ -z "$getRootFS" ]; then
    log "Error: No Btrfs root filesystem found in /etc/fstab.bak."
    exit 1
fi

# List of expected subvolumes and mount points
declare -A subvolumes=(
    [@]="/"
    #[@home]="/home"
    #[@log]="/var/log"
    #[@tmp]="/var/tmp"
    [@cache]="/var/cache"
    [@snapshots]="/.snapshots"
)

# Mount root volume if needed to create subvols
if ! mountpoint -q /mnt; then
    mount -o subvol=/ "$getRootFS" /mnt 2>/dev/null || {
        log "Error: Failed to mount $getRootFS on /mnt."
        exit 1
    }
fi

# Create subvolumes
log "Creating Btrfs subvolumes..."
for subvol in "${!subvolumes[@]}"; do
    subvolPath="/mnt/${subvol#/}"
    if [ ! -d "$subvolPath" ]; then
        mkdir -p "$(dirname "$subvolPath")"
        btrfs subvolume create "$subvolPath"
        log "Created subvolume: $subvol"
    else
        log "Subvolume already exists: $subvol"
    fi
done

# Create mount points
log "Ensuring mount points exist..."
for mountPoint in "${subvolumes[@]}"; do
    if [ ! -d "$mountPoint" ]; then
        mkdir -p "$mountPoint"
        log "Created mount point: $mountPoint"
    else
        log "Mount point already exists: $mountPoint"
    fi
done

# Unmount temporary mount
log "Cleaning up temporary mount..."
umount /mnt || {
    log "Error: Failed to unmount /mnt."
    exit 1
}

log "Generating new /etc/fstab.new..."

# Start fresh
cat <<EOF > /etc/fstab.new
# /etc/fstab: static file system information.
# generated by afreisinger/gen-fstab-plus.sh https://gist.github.com/afreisinger/ab82936d5434b83503562ed66534373e
# <file system> <mount point> <type>  <options> <dump>  <pass>
EOF

# EFI
echo -e "\n# EFI boot partition" >> /etc/fstab.new
echo "$getBootFS /boot/efi vfat defaults 0 1" >> /etc/fstab.new

# Btrfs root
echo -e "\n# Mount btrfs subvolumes" >> /etc/fstab.new

# Sort mount points by path
for subvol in $(for k in "${!subvolumes[@]}"; do
    echo "$k ${subvolumes[$k]}"
done | sort -k2 | awk '{print $1}'); do
    mountPoint="${subvolumes[$subvol]}"
    options="${btrfsOptionsBySubvol[$subvol]:-$defaultBtrfsOptions}"
    echo "$getRootFS $mountPoint btrfs subvol=$subvol,$options 0 0" >> /etc/fstab.new
done

# Swap
if [ -n "$getSwapFS" ]; then
    echo -e "\n# Swap" >> /etc/fstab.new
    echo "$getSwapFS none swap sw 0 0" >> /etc/fstab.new
fi

# Other mounts from original fstab.bak (non-Btrfs, non-vfat)
echo -e "\n# Other mounts preserved from fstab.bak" >> /etc/fstab.new
awk '$1 !~ /^#/ && $3 != "btrfs" && $3 != "vfat" && $3 != "swap" {print}' /etc/fstab.bak >> /etc/fstab.new

# OPTIONAL bind mounts (e.g. ext4 /data to /home subdirs)
if [ "$ENABLE_BIND_MOUNTS" = true ]; then
    echo -e "\n# Bind mounts from ext4 /data" >> /etc/fstab.new

    declare -A bindMounts=(
        ["/data/dev"]="/home/$USER/dev"
        ["/data/bin"]="/home/$USER/bin"
    )

    for src in "${!bindMounts[@]}"; do
        dst="${bindMounts[$src]}"
        if [ -d "$src" ]; then
            mkdir -p "$dst"
            chown "$USER:$USER" "$dst"
            echo "$src $dst none bind,nofail 0 0" >> /etc/fstab.new
            log "Configured bind mount: $src -> $dst"
        else
            log "Skipping bind mount: source $src does not exist"
        fi
    done
else
    log "Bind mounts from /data are disabled (ENABLE_BIND_MOUNTS=false)"
fi

# CIFS mount
if [ "$ENABLE_CIFS_MOUNT" = true ]; then
    echo -e "\n# CIFS network share" >> /etc/fstab.new

    # Install cifs-utils if missing
    if ! command -v mount.cifs >/dev/null 2>&1; then
        log "cifs-utils package not found. Installing..."
        apt-get update && apt-get install -y cifs-utils || {
            log "Error: Failed to install cifs-utils. Please install manually."
            exit 1
        }
    else
        log "cifs-utils already installed."
    fi

    if [ ! -f "$CIFS_CREDENTIALS" ]; then
        log "No credentials file found at $CIFS_CREDENTIALS"
        read -p "Enter CIFS username: " CIFS_USER_INPUT
        read -s -p "Enter CIFS password: " CIFS_PASS_INPUT
        echo

        cat <<EOF > "$CIFS_CREDENTIALS"
username=$CIFS_USER_INPUT
password=$CIFS_PASS_INPUT
EOF
        chmod 600 "$CIFS_CREDENTIALS"
        log "Credentials file created at $CIFS_CREDENTIALS"
    else
        log "Credentials file already exists at $CIFS_CREDENTIALS"
    fi

    mkdir -p "$CIFS_TARGET"
    echo "$CIFS_SOURCE $CIFS_TARGET cifs $CIFS_OPTIONS 0 0" >> /etc/fstab.new
    log "Configured CIFS mount: $CIFS_SOURCE -> $CIFS_TARGET"
fi

# Attempt to mount if not already mounted
if [ "$ENABLE_CIFS_MOUNT" = true ]; then
    if ! mountpoint -q "$CIFS_TARGET"; then
        log "Mounting CIFS share at $CIFS_TARGET..."
        mount -t cifs "$CIFS_SOURCE" "$CIFS_TARGET" -o "$CIFS_OPTIONS" || {
            log "Error: Failed to mount CIFS share at $CIFS_TARGET."
        }
    else
        log "CIFS share already mounted at $CIFS_TARGET."
    fi
fi

log "New fstab saved to /etc/fstab.new"
log "Summary of new /etc/fstab.new (non-comment lines):"
echo
grep -vE '^\s*#|^\s*$' /etc/fstab.new
echo


# Confirmar reemplazo de fstab
read -rp "Do you want to replace /etc/fstab with the new version? [y/N]: " confirm_fstab
if [[ "$confirm_fstab" =~ ^[Yy]$ ]]; then
    log "Replacing /etc/fstab with new version"
    cp /etc/fstab.new /etc/fstab
    systemctl daemon-reload

    # Confirmar si desea ejecutar mount -a
    read -rp "Do you want to run 'mount -a' now? [y/N]: " confirm_mount
    if [[ "$confirm_mount" =~ ^[Yy]$ ]]; then
            log "User chose to run 'mount -a'"
        if mount -a; then
            log "'mount -a' completed successfully."
            log "verify mount."
            verify_mounts
        else
            log "Error during 'mount -a'."
            exit 1
        fi
    else
        log "User skipped 'mount -a'"
    fi
else
    log "User declined to replace fstab. Skipping mount -a"
fi

GitHub repo