I’ve been setting up yet another remote backup lately (see associated problem here). For this purpose (on Unix), the duplicity solution looks ideal. However, I’ve tried it on a couple of lightweight FTP servers (a TL-WDR3600 and a Raspberry Pi) and neither of them work. I keep getting a “Permission Denied” message.
I did quite a bit of investigation, and found that it’s related to the way that duplicity’s FTP backend, ncftp/ncftpput sends files. Or really, a quirk of vsftpd, where it won’t let you put a file with an absolute path (and more specifically a file with a directory name). I’ve seen other reports of this on the Internet here and here.
Here’s a sample ncftpput debug log:
2014-06-25 00:56:34 331: Please specify the password.
2014-06-25 00:56:34 Cmd: PASS xxxxxxxx
2014-06-25 00:56:34 230: Login successful.
2014-06-25 00:56:34 Cmd: PWD
2014-06-25 00:56:34 257: "/"
2014-06-25 00:56:34 Logged in to 192.168.1.2 as Poojan.
2014-06-25 00:56:34 Cmd: FEAT
2014-06-25 00:56:34 211: Features:
2014-06-25 00:56:34 EPRT
2014-06-25 00:56:34 EPSV
2014-06-25 00:56:34 MDTM
2014-06-25 00:56:34 PASV
2014-06-25 00:56:34 REST STREAM
2014-06-25 00:56:34 SIZE
2014-06-25 00:56:34 TVFS
2014-06-25 00:56:34 UTF8
2014-06-25 00:56:34 End
2014-06-25 00:56:34 Cmd: PWD
2014-06-25 00:56:34 257: "/"
2014-06-25 00:56:34 Cmd: CWD folder1/duplicity/Public
2014-06-25 00:56:34 250: Directory successfully changed.
2014-06-25 00:56:34 Cmd: CWD /
2014-06-25 00:56:34 250: Directory successfully changed.
2014-06-25 00:56:34 Cmd: TYPE I
2014-06-25 00:56:34 200: Switching to Binary mode.
2014-06-25 00:56:34 Cmd: PASV
2014-06-25 00:56:34 227: Entering Passive Mode (192,168,1,2,225,89).
2014-06-25 00:56:34 Cmd: STOR folder1/duplicity/Public/duplicity-full.20140625T055614Z.vol1.difftar.gpg
2014-06-25 00:56:34 550: Permission denied.
2014-06-25 00:56:34 ncftpput folder1/duplicity/Public/duplicity-full.20140625T055614Z.vol1.difftar.gpg: server said: Permission denied.
2014-06-25 00:56:34 Cmd: QUIT
2014-06-25 00:56:34 221: Goodbye.
However, I ran a few tests, and I found that if one cd‘es to the directory and then puts (STOR‘es) the file, everything works. My guess this is a chroot-style feature. So, I created a small Python script that will parse the arguments that duplicity sends, and inserts cd (to the target directory) command before uploading the file. This works well. Here’s the script:
#!/usr/local/bin/python3
import argparse
import subprocess
import sys
import os
# ncftpput looks something like this:
# 'ncftpput -f /tmp/duplicity-yRftm3-tempdir/mkstemp-PiYFTL-1 -F -t 30 -o useCLNT=0,useHELP_SITE=0 -m -V -C '/tmp/duplicity-yRftm3-tempdir/mktemp-sWc1AA-3' 'folder1/duplicity/Public/duplicity-full.20140625T041147Z.vol1.difftar.gz
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='wrapper for ncftpput command, to allow absolute target paths on vsftpd')
parser.add_argument('-f', dest='credentials_file')
parser.add_argument('-F', action='store_true')
parser.add_argument('-t', dest='timeout')
parser.add_argument('-o', dest='ftp_options')
parser.add_argument('-m', action='store_true')
parser.add_argument('-C', action='store_true')
parser.add_argument('-V', action='store_true')
parser.add_argument('source')
parser.add_argument('dest')
args = parser.parse_args()
# print(args)
dest_dir = os.path.dirname(args.dest)
dest_file = os.path.basename(args.dest)
#cmd_args = ['/usr/local/bin/ncftpput', '-d', 'ftp-debug.log', '-W', 'cd {0}'.format(dest_dir)] + sys.argv[1:-1] + [dest_file]
cmd_args = ['/usr/local/bin/ncftpput', '-W', 'cd {0}'.format(dest_dir)] + sys.argv[1:-1] + [dest_file]
subprocess.Popen(cmd_args)
The script is called ncftpput, and is placed in a directory called ~/duplicity_bin. I then add this directory to my path before running duplicity. Here’s a shell script that does that:
#!/bin/sh
export FTP_PASSWORD="XXXYYYXXYXYZY"
export PATH="/home/Poojan/duplicity_bin:$PATH"
duplicity -v 9 --encrypt-key=DEADBEEF full /tank/Users/Public ftp://Poojan@192.168.1.2/folder1/duplicity/Public
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