Fixing wget “Cannot Write To” Error During Large File Downloads

When using wget for mirroring large files across servers, many users encounter the frustrating "Cannot write to" error that terminates downloads prematurely. This typically occurs when:

wget -x -N -i http://domain.com/filelist.txt

File sizes exceed 2GB (common with -N timestamping)
Destination filesystem has space limitations
Character encoding issues in terminal output
Incomplete partial downloads causing verification failures

The problem stems from multiple technical factors interacting:

--2012-08-31 12:41:19--  http://domain.com/path/to/file.zip
Length: 5502192869 (5.1G) [application/zip]
Cannot write to âdomain.com/path/to/file.zipâ

Key observations from the error pattern:

Consistent failure around 200MB-3GB range
Character encoding artifacts (â symbols)
Timestamp verification conflicts with existing partial files

Option 1: Disable Timestamp Verification

For large files, temporarily omit -N flag:

wget -x -c -i http://domain.com/filelist.txt

The -c enables resuming interrupted downloads

Option 2: Filesystem Workarounds

# Create download directory with sufficient inodes
mkdir -p /data/downloads
chmod 1777 /data/downloads

# Mount with large file support
mount -o remount,rw,noatime,nodiratime /data

Option 3: Alternative Download Methods

For extremely large files, consider:

# Using curl with progress bar
curl -L -C - -o file.zip http://domain.com/path/to/file.zip

# Parallel download with aria2
aria2c -x16 -s16 http://domain.com/path/to/file.zip

The â symbols indicate terminal encoding mismatch. Force UTF-8:

LC_ALL=en_US.UTF-8 wget -x -N http://domain.com/path/to/file.zip

When standard solutions fail:

# Debug filesystem limits
df -h
df -i
ulimit -a

# Verify network stability
mtr --report domain.com

# Check for antivirus interference
systemctl stop clamav-daemon

Implement download chunking for files >2GB
Schedule transfers during low-traffic periods
Monitor disk I/O during transfers (iotop -o)
Consider using rsync for regular mirroring

# Sample rsync alternative
rsync -avz --partial --progress user@remote:/path/ /local/path/

When using wget to transfer large files (particularly those over 2GB), many developers encounter a frustrating scenario where downloads abruptly terminate with a "Cannot write to [filename]" error. This typically occurs after transferring approximately 200MB-3GB of data, regardless of the actual file size.

--2023-11-15 09:30:00--  http://example.com/large_file.iso
...
3% [====> ] 213,003,412 8.74M/s   in 24s
Cannot write to âexample.com/large_file.isoâ

Based on extensive troubleshooting, these are the most likely culprits:

Filesystem limitations: The destination filesystem might have file size restrictions (common with FAT32's 4GB limit)
Disk space issues: Insufficient space or quota restrictions
Character encoding problems: The "â" characters in the error suggest encoding issues
wget version limitations: Older versions may have large file handling bugs

Solution 1: Use wget's Continue Option

The most effective approach is to utilize wget's built-in resume capability:

wget -c -x -N http://domain.com/path/to/file.zip

Key flags:

-c: Continue partial downloads
-x: Preserve directory structure
-N: Timestamping for new files only

Solution 2: Verify Filesystem Compatibility

Check your destination filesystem type and limitations:

df -Th /path/to/destination

For large files (>4GB), ensure you're using a modern filesystem like ext4, NTFS, or XFS.

Solution 3: Alternative Download Methods

If wget persists in failing, consider these alternatives:

# Using curl
curl -O -C - http://domain.com/path/to/file.zip

# Using rsync (if supported)
rsync -avzP user@remote:/path/to/file.zip /local/path/

For persistent cases, try these advanced techniques:

# 1. Specify output filename explicitly
wget -O /tmp/download_file.zip http://domain.com/path/to/file.zip

# 2. Force ASCII mode (for encoding issues)
wget --restrict-file-names=ascii -x -N http://domain.com/path/to/file.zip

# 3. Use newer wget version
wget --version
# Consider upgrading if below 1.20

Always use -c flag for large downloads
Monitor disk space with df -h before starting transfers
Consider splitting large files when possible
For scripts, implement error handling and retry logic

Here's a robust bash script to handle intermittent failures:

#!/bin/bash

MAX_RETRIES=5
RETRY_DELAY=30
URL="http://domain.com/path/to/file.zip"

for ((i=1; i<=$MAX_RETRIES; i++)); do
    wget -c -x -N "$URL"
    if [ $? -eq 0 ]; then
        echo "Download completed successfully"
        exit 0
    fi
    echo "Attempt $i failed. Retrying in $RETRY_DELAY seconds..."
    sleep $RETRY_DELAY
done

echo "Maximum retries reached. Download failed."
exit 1

ServerDevWorker