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