Change all UID and GID from old system to new system

replace_uidgid.py

# Replacing all UID, GID in directorary
# Requirement: python3.6
# Usage: python3 replace_uidgid.py old_etc_passwd old_etc_group new_etc_passwd new_etc_group /home --dry-run -vv
# Author: linnil1
import os
import argparse
from collections import defaultdict
import pathlib


def readUser(file_path):
    """
    Read /etc/passwd or /etc/group like file

    return:
      {name: id}
    """
    users = {}
    for row in open(file_path):
        row = row.split(":")
        users[row[0]] = int(row[2])
    return users


def old2newMapping(old_user, new_user, default_id, default_name):
    """
    Map old uid to new uid and name

    return:
      {old_id: {'oldname': "", 'newname': "", 'newid': 0}}
    """
    id_map = defaultdict(lambda: dict({
        'oldname': default_name,
        'newname': default_name,
        'newid':   default_id
    }))

    for name, id in old_user.items():
        id_map[id]['oldname'] = name
        if name in new_user:
            id_map[id]['newname'] = name
            id_map[id]['newid'] = new_user[name]

    return id_map


def mappingSummary(id_map):
    for i in sorted(id_map.keys()):
        v = max(20 - len(id_map[i]['oldname']), 0)
        print(f"{i:6}({id_map[i]['oldname']}) {' ' * v} ->"
              f"{id_map[i]['newid']:6}({id_map[i]['newname']})")


def walk(path):
    """
    Triversal all the file in the path

    yield:
      (path, uid, gid)
    """
    # root
    if os.path.exists(path):
        stat = os.stat(path)
        yield (path, stat.st_uid, stat.st_gid)

    # tree
    for dirpath, dirnames, filenames in os.walk(path):
        for i in filenames + dirnames:
            f = os.path.join(dirpath, i)
            if os.path.exists(f):
                stat = os.stat(f)
                yield (f, stat.st_uid, stat.st_gid)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description='Replace all uid,gid')
    parser.add_argument('old_passwd', type=pathlib.Path)
    parser.add_argument('old_group', type=pathlib.Path)
    parser.add_argument('new_passwd', type=pathlib.Path)
    parser.add_argument('new_group', type=pathlib.Path)
    parser.add_argument('path', type=pathlib.Path)
    parser.add_argument('--default-uid', dest="default_uid", type=int, default=1000)
    parser.add_argument('--default-gid', dest="default_gid", type=int, default=1000)
    parser.add_argument('--default-name', dest="default_name", type=str, default="Anonymous")
    parser.add_argument('--dry-run', dest="dry_run", action='store_true')
    parser.add_argument('--verbose', '-v', action='count', default=0)
    args = parser.parse_args()

    # main
    old_user = readUser(args.old_passwd)
    new_user = readUser(args.new_passwd)
    old_group = readUser(args.old_group)
    new_group = readUser(args.new_group)
    user_map = old2newMapping(old_user, new_user, args.default_uid, args.default_name)
    group_map = old2newMapping(old_group, new_group, args.default_gid, args.default_name)

    print("UID Summary")
    mappingSummary(user_map)
    print("GID Summary")
    mappingSummary(group_map)

    print(f"Replacing UID, GID in {args.path} ...")
    for path, uid, gid in walk(args.path):
        new_uid, new_gid = user_map[uid]['newid'], group_map[gid]['newid']
        if args.verbose > 0:
            print(path)
        if args.verbose > 1:
            print(f"  uid: {uid}({user_map[uid]['oldname']}) -> {new_uid}({user_map[uid]['newname']})", end=",")
            print(f"  gid: {gid}({group_map[gid]['oldname']}) -> {new_gid}({group_map[gid]['newname']})")
        if not args.dry_run:
            os.chown(path, new_uid, new_gid)
    print("Done")