{"id":303,"date":"2009-04-16T22:37:43","date_gmt":"2009-04-16T15:37:43","guid":{"rendered":"http:\/\/adityo.blog.binusian.org\/?p=303"},"modified":"2009-04-16T22:56:21","modified_gmt":"2009-04-16T15:56:21","slug":"useradd-comand","status":"publish","type":"post","link":"https:\/\/adityo.blog.binusian.org\/?p=303","title":{"rendered":"Useradd comand"},"content":{"rendered":"

Today i just got a question on how actually a useradd command works and is it possible for us to create user without useradd command. And here is my answer after some googling around \ud83d\ude06<\/p>\n

what is useradd ?<\/span><\/p>\n

useradd COMMAND:<\/strong>
\nuseradd – Adds new user to the linux system, with specified user-name. When a new user is added then a corresponding entry is made in files \/etc\/passwd, \/etc\/group and \/etc\/shadow<\/p>\n

SYNTAX:<\/strong>
\nThe Syntax is
\nuseradd [options] [username]<\/span><\/p>\n

OPTIONS:<\/strong><\/p>\n

# useradd –help<\/p>\n

Usage: useradd [options] LOGIN<\/p>\n

Options:<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
-b, –base-dir BASE_DIR<\/td>\nbase directory for the new user account home directory<\/td>\n<\/tr>\n
-c, –comment COMMENT<\/td>\nset the GECOS field for the new user account<\/td>\n<\/tr>\n
-d, –home-dir HOME_DIR<\/td>\nhome directory for the new user account<\/td>\n<\/tr>\n
-D, –defaults<\/td>\nprint or save modified default useradd configuration<\/td>\n<\/tr>\n
-e, –expiredate EXPIRE_DATE<\/td>\nset account expiration date to EXPIRE_DATE<\/td>\n<\/tr>\n
-f, –inactive INACTIVE<\/td>\nset password inactive after expiration to INACTIVE<\/td>\n<\/tr>\n
-g, –gid GROUP<\/td>\nforce use GROUP for the new user account<\/td>\n<\/tr>\n
-G, –groups GROUPS<\/td>\nlist of supplementary groups for the new user account<\/td>\n<\/tr>\n
-h, –help<\/td>\ndisplay this help message and exit<\/td>\n<\/tr>\n
-k, –skel SKEL_DIR<\/td>\nspecify an alternative skel directory<\/td>\n<\/tr>\n
-K, –key KEY=VALUE<\/td>\noverrides \/etc\/login.defs defaults<\/td>\n<\/tr>\n
-m, –create-home<\/td>\ncreate home directory for the new user account<\/td>\n<\/tr>\n
-o, –non-unique<\/td>\nallow create user with duplicate (non-unique) UID<\/td>\n<\/tr>\n
-p, –password PASSWORD<\/td>\nuse encrypted password for the new user account<\/td>\n<\/tr>\n
-r, –system<\/td>\ncreate a system account<\/td>\n<\/tr>\n
-s, –shell SHELL<\/td>\nthe login shell for the new user account<\/td>\n<\/tr>\n
-u, –uid UID<\/td>\nforce use the UID for the new user account<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

EXAMPLE:<\/strong><\/p>\n

    \n
  1. To add new user:\n
    # useradd test<\/span><\/pre>\n
    This command will add a new user with name test.<\/li>\n
  2. To add user but not allow to login in the system:\n
    useradd -s \/bin\/nologin test<\/span><\/pre>\n
    This command will add user hiox but not allow to login. Or you can go to the \/etc\/passwd and set the test username\u00a0 Shell access tobe <\/em>\/usr\/sbin\/nologin or \/usr\/sbinfalse<\/p>\n
    Understanding fields in \/etc\/passwd<\/h2>\n
    The \/etc\/passwd contains one entry per line for each user (or user account) of the system. All fields are separated by a colon (:) symbol. Total seven fields as follows.<\/p>\n
    Generally, passwd file entry looks as follows (click to enlarge image):<\/p>\n
    \"\"<\/a><\/p>\n
      \n
    1. Username<\/strong>:      It is used when user logs in. It should be between 1 and 32 characters in      length.<\/li>\n
    2. Password<\/strong>:      An x character indicates that encrypted password is stored in \/etc\/shadow      file.<\/li>\n
    3. User ID (UID)<\/strong>:      Each user must be assigned a user ID (UID). UID 0 (zero) is reserved for      root and UIDs 1-99 are reserved for other predefined accounts. Further UID      100-999 are reserved by system for administrative and system      accounts\/groups.<\/li>\n
    4. Group ID (GID)<\/strong>:      The primary group ID (stored in \/etc\/group file)<\/li>\n
    5. User ID Info<\/strong>:      The comment field. It allow you to add extra information about the users      such as user’s full name, phone number etc. This field use by finger      command.<\/li>\n
    6. Home directory<\/strong>:      The absolute path to the directory the user will be in when they log in.      If this directory does not exists then users directory becomes \/<\/li>\n
    7. Command\/shell<\/strong>:      The absolute path of a command or shell (\/bin\/bash). Typically, this is a      shell. Please note that it does not have to be a shell.<\/li>\n<\/ol>\n\n\n\n\n\n
      In above command:<\/td>\n<\/tr>\n
      test<\/td>\n-Is the user-name<\/td>\n<\/tr>\n
      \/bin\/nologin<\/td>\n-Is Shell assigned to the user<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/li>\n
    8. To set expire date of the user:\n
      useradd -e 2008-06-30 test<\/span><\/pre>\n
      This command will add user test and set the expire date to 2009-06-30.<\/p>\n\n\n\n\n\n
      In above command:<\/td>\n<\/tr>\n
      test<\/td>\n-Is the user-name<\/td>\n<\/tr>\n
      2009-06-30<\/td>\n-Is date on which the user-account will be expired<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/li>\n
    9. To create user without creating home directory:\n
      useradd -M test<\/span><\/pre>\n
      The above command will create user test but home directory will not be created.<\/li>\n<\/ol>\n
      How to add user without useradd command ?<\/p>\n
      as you probably know useradd command actualy create a user on \/etc\/passwd to determine the user id home directory comman shell etc, \/etc\/group to determine te group id and \/etc\/shadow for password. I will create a newtest username but since the password was encrpty MD5 i will use the previous username password on the newtest username that we will create withiut useradd command<\/p>\n
      \n
      Code:<\/div>\n
      # useradd testing\r\n# passwd testing\r\nNew password: password<\/em>\r\nRe-enter new password: password<\/em>\r\nPassword changed.\r\n#\r\n# cat \/etc\/shadow | grep testing\r\ntesting:$1$AdHBr9EJ$VwEqlF.GprlX28oWWYprZ0:14313:0:99999:7:::\r\n#\r\n# cat \/etc\/passwd | grep testing\r\ntesting:x:1001:1001::\/home\/tesing:\/bin\/sh\r\n# cat \/etc\/group | grep testing\r\ntesting:x:1001:\r\n\r\nCreate newtest username without adduser command\r\n# vi \/etc\/shadow\r\nadd newtest password and save\r\nnewtest:$1$AdHBr9EJ$VwEqlF.GprlX28oWWYprZ0:14313:0:99999:7:::\r\n# vi \/etc\/group\r\nadd newtest username group and id (makesure u have use the new id number\r\nnewtest:x:1002:\r\n# vi \/etc\/passwd\r\nadd newtest username,id,home directory ,shell command\r\nnewtest:x:1002:1002::\/home:\/bin\/sh<\/pre>\n<\/div>\n
      Of course, this is my version of creating a user without useradd command. Please correct me if i am wrong<\/p>\n","protected":false},"excerpt":{"rendered":"
      Today i just got a question on how actually a useradd command works and is it possible for us to create user without useradd command. And here is my answer after some googling around \ud83d\ude06 what is useradd ? useradd COMMAND: useradd – Adds new user to the linux system, with specified user-name. When a […]<\/p>\n","protected":false},"author":386,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1357],"tags":[1358],"class_list":["post-303","post","type-post","status-publish","format-standard","hentry","category-commands","tag-useradd-comand"],"_links":{"self":[{"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=\/wp\/v2\/posts\/303","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=\/wp\/v2\/users\/386"}],"replies":[{"embeddable":true,"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=303"}],"version-history":[{"count":3,"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=\/wp\/v2\/posts\/303\/revisions"}],"predecessor-version":[{"id":305,"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=\/wp\/v2\/posts\/303\/revisions\/305"}],"wp:attachment":[{"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=303"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=303"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/adityo.blog.binusian.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=303"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}