Auto Expand Disk size via cron

pje February 11, 2025

First prep the system for the auto expand script

# Create directory for the script to live in
sudo mkdir -p /etc/expand-disk

Add the Script to crontab to run every 15 minutes

echo "*/15 * * * * /etc/expand-disk/auto-expand-disk.sh" | sudo tee -a /etc/crontab

Save the script in /etc/expand-disk/auto-expand-disk.sh (Full copy-paste command is present below this codeblock

#!/bin/bash

# Define log file
LOG_FILE="/var/log/expand_disk.log"
touch "$LOG_FILE"
chmod 666 "$LOG_FILE"


# Disk and partition
DISK="/dev/sdb"
PARTITION="/dev/sdb1"

# Logging function
log() {
    echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" | tee -a "$LOG_FILE" >/dev/null 2>&1
}

log "Starting disk expansion check for $PARTITION"

# Ensure required tools are installed
for cmd in lsblk growpart resize2fs partprobe; do
    if ! command -v "$cmd" &>/dev/null; then
        log "Error: $cmd not found. Install the necessary package."
        exit 1
    fi
done

# Trigger a disk rescan
log "Rescanning disk $DISK for changes..."
echo 1 > /sys/class/block/${DISK##*/}/device/rescan 2>/dev/null
partprobe "$DISK" 2>/dev/null

# Get disk and partition size
AVAILABLE_SPACE=$(lsblk -b -n -o NAME,SIZE | grep -w "$(basename "$DISK")" | awk '{print $2}')
PARTITION_END=$(lsblk -b -n -o NAME,SIZE | grep -w "$(basename "$PARTITION")" | awk '{print $2}')

# Debugging output
log "Disk total size: ${AVAILABLE_SPACE:-'UNKNOWN'} bytes"
log "Partition size: ${PARTITION_END:-'UNKNOWN'} bytes"

# Ensure values are retrieved correctly
if [ -z "$AVAILABLE_SPACE" ] || [ -z "$PARTITION_END" ]; then
    log "Error: Could not determine disk or partition size."
    exit 1
fi

# Check if there is unallocated space
if (( PARTITION_END >= AVAILABLE_SPACE )); then
    log "No unallocated space available on $DISK."
    exit 0
fi

# Expand partition
log "Expanding partition $PARTITION"
growpart "$DISK" 1
if [ $? -ne 0 ]; then
    log "Error: Failed to expand partition."
    exit 1
fi

# Trigger another rescan after expansion
log "Triggering another rescan after partition expansion..."
partprobe "$DISK"
sleep 2

# Resize filesystem
log "Resizing filesystem on $PARTITION"
resize2fs "$PARTITION"
if [ $? -ne 0 ]; then
    log "Error: Failed to resize filesystem."
    exit 1
fi

log "Successfully expanded $PARTITION"
exit 0

For creating the file directly via a copy/paste use this

sudo tee /etc/expand-disk/auto-expand-disk.sh <<EOF
#!/bin/bash

# Define log file
LOG_FILE="/var/log/expand_disk.log"
touch "$LOG_FILE"
chmod 666 "$LOG_FILE"

# Disk and partition
DISK="/dev/sdb"
PARTITION="/dev/sdb1"

# Logging function
log() {
    echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" | tee -a "$LOG_FILE" >/dev/null 2>&1
}

log "Starting disk expansion check for $PARTITION"

# Ensure required tools are installed
for cmd in lsblk growpart resize2fs partprobe; do
    if ! command -v "$cmd" &>/dev/null; then
        log "Error: $cmd not found. Install the necessary package."
        exit 1
    fi
done

# Trigger a disk rescan
log "Rescanning disk $DISK for changes..."
echo 1 > /sys/class/block/${DISK##*/}/device/rescan 2>/dev/null
partprobe "$DISK" 2>/dev/null

# Get disk and partition size
AVAILABLE_SPACE=$(lsblk -b -n -o NAME,SIZE | grep -w "$(basename "$DISK")" | awk '{print $2}')
PARTITION_END=$(lsblk -b -n -o NAME,SIZE | grep -w "$(basename "$PARTITION")" | awk '{print $2}')

# Debugging output
log "Disk total size: ${AVAILABLE_SPACE:-'UNKNOWN'} bytes"
log "Partition size: ${PARTITION_END:-'UNKNOWN'} bytes"

# Ensure values are retrieved correctly
if [ -z "$AVAILABLE_SPACE" ] || [ -z "$PARTITION_END" ]; then
    log "Error: Could not determine disk or partition size."
    exit 1
fi

# Check if there is unallocated space
if (( PARTITION_END >= AVAILABLE_SPACE )); then
    log "No unallocated space available on $DISK."
    exit 0
fi

# Expand partition
log "Expanding partition $PARTITION"
growpart "$DISK" 1
if [ $? -ne 0 ]; then
    log "Error: Failed to expand partition."
    exit 1
fi

# Trigger another rescan after expansion
log "Triggering another rescan after partition expansion..."
partprobe "$DISK"
sleep 2

# Resize filesystem
log "Resizing filesystem on $PARTITION"
resize2fs "$PARTITION"
if [ $? -ne 0 ]; then
    log "Error: Failed to resize filesystem."
    exit 1
fi

log "Successfully expanded $PARTITION"
exit 0

EOF

pje

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