mailinabox/management/backup.py

120 lines
4.2 KiB
Python
Executable File

#!/usr/bin/python3
# This script performs a backup of all user data:
# 1) System services are stopped while a copy of user data is made.
# 2) An incremental backup is made using duplicity into the
# directory STORAGE_ROOT/backup/duplicity.
# 3) The stopped services are restarted.
# 4) The backup files are encrypted with a long password (stored in
# backup/secret_key.txt) to STORAGE_ROOT/backup/encrypted.
# 5) STORAGE_ROOT/backup/after-backup is executd if it exists.
import sys, os, os.path, shutil, glob
from utils import exclusive_process, load_environment, shell
# settings
full_backup = "--full" in sys.argv
keep_backups_for = "31D" # destroy backups older than 31 days except the most recent full backup
env = load_environment()
exclusive_process("backup")
# Ensure the backup directory exists.
backup_dir = os.path.join(env["STORAGE_ROOT"], 'backup')
backup_duplicity_dir = os.path.join(backup_dir, 'duplicity')
os.makedirs(backup_duplicity_dir, exist_ok=True)
# On the first run, always do a full backup. Incremental
# will fail.
if len(os.listdir(backup_duplicity_dir)) == 0:
full_backup = True
else:
# When the size of incremental backups exceeds the size of existing
# full backups, take a new full backup. We want to avoid full backups
# because they are costly to synchronize off-site.
full_sz = sum(os.path.getsize(f) for f in glob.glob(backup_duplicity_dir + '/*-full.*'))
inc_sz = sum(os.path.getsize(f) for f in glob.glob(backup_duplicity_dir + '/*-inc.*'))
# (n.b. not counting size of new-signatures files because they are relatively small)
if inc_sz > full_sz * 1.5:
full_backup = True
# Stop services.
shell('check_call', ["/usr/sbin/service", "dovecot", "stop"])
shell('check_call', ["/usr/sbin/service", "postfix", "stop"])
# Update the backup mirror directory which mirrors the current
# STORAGE_ROOT (but excluding the backups themselves!).
try:
shell('check_call', [
"/usr/bin/duplicity",
"full" if full_backup else "incr",
"--no-encryption",
"--archive-dir", "/tmp/duplicity-archive-dir",
"--name", "mailinabox",
"--exclude", backup_dir,
"--volsize", "100",
"--verbosity", "warning",
env["STORAGE_ROOT"],
"file://" + backup_duplicity_dir
])
finally:
# Start services again.
shell('check_call', ["/usr/sbin/service", "dovecot", "start"])
shell('check_call', ["/usr/sbin/service", "postfix", "start"])
# Remove old backups. This deletes all backup data no longer needed
# from more than 31 days ago. Must do this before destroying the
# cache directory or else this command will re-create it.
shell('check_call', [
"/usr/bin/duplicity",
"remove-older-than",
keep_backups_for,
"--archive-dir", "/tmp/duplicity-archive-dir",
"--name", "mailinabox",
"--force",
"--verbosity", "warning",
"file://" + backup_duplicity_dir
])
# Remove duplicity's cache directory because it's redundant with our backup directory.
shutil.rmtree("/tmp/duplicity-archive-dir")
# Encrypt all of the new files.
backup_encrypted_dir = os.path.join(backup_dir, 'encrypted')
os.makedirs(backup_encrypted_dir, exist_ok=True)
for fn in os.listdir(backup_duplicity_dir):
fn2 = os.path.join(backup_encrypted_dir, fn) + ".enc"
if os.path.exists(fn2): continue
# Encrypt the backup using the backup private key.
shell('check_call', [
"/usr/bin/openssl",
"enc",
"-aes-256-cbc",
"-a",
"-salt",
"-in", os.path.join(backup_duplicity_dir, fn),
"-out", fn2,
"-pass", "file:%s" % os.path.join(backup_dir, "secret_key.txt"),
])
# The backup can be decrypted with:
# openssl enc -d -aes-256-cbc -a -in latest.tgz.enc -out /dev/stdout -pass file:secret_key.txt | tar -z
# Remove encrypted backups that are no longer needed.
for fn in os.listdir(backup_encrypted_dir):
fn2 = os.path.join(backup_duplicity_dir, fn.replace(".enc", ""))
if os.path.exists(fn2): continue
os.unlink(os.path.join(backup_encrypted_dir, fn))
# Execute a post-backup script that does the copying to a remote server.
# Run as the STORAGE_USER user, not as root. Pass our settings in
# environment variables so the script has access to STORAGE_ROOT.
post_script = os.path.join(backup_dir, 'after-backup')
if os.path.exists(post_script):
shell('check_call',
['su', env['STORAGE_USER'], '-c', post_script],
env=env)