[리눅스 명령어] usermod

usermod

I. 개념

사용자 계정 관리 : usermod

• 사용자와 관련하여 대부분의 정보를 변경할 수 있음.
  • 셀
  • 홈 디렉터리
  • 그룹
  • UID
  • GID

사용법

# usermod [option] 사용자 계정

• -d
  • 사용자의 홈 디렉터리 변경
  • 변경할 디렉터리는 미리 생성되어야 함.
  • -m과 같이 사용할 경우
    • 사용하던 홈 디렉터리의 파일과 디렉터리도 같이 옮겨줌.
      • 디렉터리를 따로 생성하지 않아도 됨.
  • --home
• -m
  • 사용자의 홈 디렉터리 변경 시, 기존에 사용하던 파일 및 디렉터리를 옮겨주는 옵션
  • -d와 함께 쓰임.
  • --move-home
• -g
  • 사용자의 그룹 변경
• -s
  • 사용자의 셀 변경
• -u
  • 사용자의 UID 값 변경
• -e
  • 계정 만기일 변경
  • YYYY-MM-DD 또는 MM/DD/YY 형태로 지정
• -f
  • 패스워드 만기일이 지난 후, 패스워드에 LOCK 을 설정할 유예 기간 지정
• -c
  • 사용자의 간단한 정보를 입력하거나 변경
• -G
  • 추가로 다른 그룹에 속하게 할 때 사용
• -a
  • -G 옵션과 같이 사용하는 옵션
  • 기존의 2차 그룹 이외에 추가로 2차 그룹을 지정할 때 사용
  • --append
• -p
  • /etc/shadow의 2번째 필드인 암호화된 패스워드 값을 변경할 때 사용
  • 이 옵션을 사용할 때는, 암호화된 값을 지정해야 함.
• -l
  • 사용자 아이디 변경
  • --login
• -L
  • 사용자의 패스워드에 LOCK을 걸어 로그인을 막음.
  • --lock
• -U
  • 사용자의 패스워드에 걸린 LOCK을 풂.
  • --unlock

사용 예

• starrykss 라는 사용자의 홈 디렉터리를 /home2/starrykss로 변경하고, 내용도 새로운 위치로 옮겨줌. (-m)
• 단, /home2라는 디렉터리는 미리 생성되어 있어야 함.

# usermod -d /home2/starrykss -m starrykss

• drone이라는 사용자의 그룹을 terran으로 변경

# usermod -g terran drone

• starrykss라는 사용자의 셀을 /bin/false로 바꾸지만, 실질적으로 존재하는 셀이 아니므로 일시적인 사용자의 계정을 제한할 때 씀.

# usermod -s /bin/false starrykss

• jalin이라는 사용자의 계정 만기일을 2012년 12월 22일로 지정

# usermod -e 2012-12-22 jalin

• starrykss라는 사용자를 IHD라는 그룹에 추가로 속하게 함.

# usermod -G IHD starrykss

• starrykss라는 아이디를 yuloje로 변경

# usermod -l yuloje starrykss

참고 사용자 ID 변경 시 고려할 점

• 사용자 ID 를 변경할 경우, 사용자의 홈 디렉터리 도 고려해야 함.
• 보통 starykss 사용자의 홈 디렉터리가 /home/starrykss 임.
• 만약 아이디를 pegasus로 변경한다면, 관리자가 알아서 홈 디렉터리도 /home/pegasus로 변경해야 함.
• 따라서 아이디 변경 시, -l만 사용할 것이 아니라 -d, -m도 같이 사용해야 함.

# usermod -l pegasus -d /home/pegasus -m starrykss

 

---

II. MAN 명령어로 살펴보기

USERMOD(8)                System Management Commands                USERMOD(8)



NAME
       usermod - modify a user account

SYNOPSIS
       usermod [options] LOGIN

DESCRIPTION
       The usermod command modifies the system account files to reflect the
       changes that are specified on the command line.

OPTIONS
       The options which apply to the usermod command are:

       -a, --append
           Add the user to the supplementary group(s). Use only with the -G
           option.

       -c, --comment COMMENT
           The new value of the user's password file comment field. It is
           normally modified using the chfn(1) utility.

       -d, --home HOME_DIR
           The user's new login directory.

           If the -m option is given, the contents of the current home
           directory will be moved to the new home directory, which is created
           if it does not already exist. If the current home directory does
           not exist the new home directory will not be created.

       -e, --expiredate EXPIRE_DATE
           The date on which the user account will be disabled. The date is
           specified in the format YYYY-MM-DD.

           An empty EXPIRE_DATE argument will disable the expiration of the
           account.

           This option requires a /etc/shadow file. A /etc/shadow entry will
           be created if there were none.

       -f, --inactive INACTIVE
           The number of days after a password expires until the account is
           permanently disabled.

           A value of 0 disables the account as soon as the password has
           expired, and a value of -1 disables the feature.

           This option requires a /etc/shadow file. A /etc/shadow entry will
           be created if there were none.

       -g, --gid GROUP
           The group name or number of the user's new initial login group. The
           group must exist.

           Any file from the user's home directory owned by the previous
           primary group of the user will be owned by this new group.

           The group ownership of files outside of the user's home directory
           must be fixed manually.

           The change of the group ownership of files inside of the user's
           home directory is also not done if the home dir owner uid is
           different from the current or new user id. This is safety measure
           for special home directories such as /.

       -G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
           A list of supplementary groups which the user is also a member of.
           Each group is separated from the next by a comma, with no
           intervening whitespace. The groups are subject to the same
           restrictions as the group given with the -g option.

           If the user is currently a member of a group which is not listed,
           the user will be removed from the group. This behaviour can be
           changed via the -a option, which appends the user to the current
           supplementary group list.

       -l, --login NEW_LOGIN
           The name of the user will be changed from LOGIN to NEW_LOGIN.
           Nothing else is changed. In particular, the user's home directory
           or mail spool should probably be renamed manually to reflect the
           new login name.

       -L, --lock
           Lock a user's password. This puts a '!' in front of the encrypted
           password, effectively disabling the password. You can't use this
           option with -p or -U.

           Note: if you wish to lock the account (not only access with a
           password), you should also set the EXPIRE_DATE to 1.

       -m, --move-home
           Move the content of the user's home directory to the new location.
           If the current home directory does not exist the new home directory
           will not be created.

           This option is only valid in combination with the -d (or --home)
           option.

           usermod will try to adapt the ownership of the files and to copy
           the modes, ACL and extended attributes, but manual changes might be
           needed afterwards.

       -o, --non-unique
           When used with the -u option, this option allows to change the user
           ID to a non-unique value.

       -p, --password PASSWORD
           The encrypted password, as returned by crypt(3).

           Note: This option is not recommended because the password (or
           encrypted password) will be visible by users listing the processes.

           You should make sure the password respects the system's password
           policy.

       -R, --root CHROOT_DIR
           Apply changes in the CHROOT_DIR directory and use the configuration
           files from the CHROOT_DIR directory.

       -P, --prefix PREFIX_DIR
           Apply changes in the PREFIX_DIR directory and use the configuration
           files from the PREFIX_DIR directory. This option does not chroot
           and is intended for preparing a cross-compilation target. Some
           limitations: NIS and LDAP users/groups are not verified. PAM
           authentication is using the host files. No SELINUX support.

       -s, --shell SHELL
           The name of the user's new login shell. Setting this field to blank
           causes the system to select the default login shell.

       -u, --uid UID
           The new numerical value of the user's ID.

           This value must be unique, unless the -o option is used. The value
           must be non-negative.

           The user's mailbox, and any files which the user owns and which are
           located in the user's home directory will have the file user ID
           changed automatically.

           The ownership of files outside of the user's home directory must be
           fixed manually.

           The change of the user ownership of files inside of the user's home
           directory is also not done if the home dir owner uid is different
           from the current or new user id. This is safety measure for special
           home directories such as /.

           No checks will be performed with regard to the UID_MIN, UID_MAX,
           SYS_UID_MIN, or SYS_UID_MAX from /etc/login.defs.

       -U, --unlock
           Unlock a user's password. This removes the '!' in front of the
           encrypted password. You can't use this option with -p or -L.

           Note: if you wish to unlock the account (not only access with a
           password), you should also set the EXPIRE_DATE (for example to
           99999, or to the EXPIRE value from /etc/default/useradd).

       -v, --add-subuids FIRST-LAST
           Add a range of subordinate uids to the user's account.

           This option may be specified multiple times to add multiple ranges
           to a users account.

           No checks will be performed with regard to SUB_UID_MIN,
           SUB_UID_MAX, or SUB_UID_COUNT from /etc/login.defs.

       -V, --del-subuids FIRST-LAST
           Remove a range of subordinate uids from the user's account.

           This option may be specified multiple times to remove multiple
           ranges to a users account. When both --del-subuids and
           --add-subuids are specified, the removal of all subordinate uid
           ranges happens before any subordinate uid range is added.

           No checks will be performed with regard to SUB_UID_MIN,
           SUB_UID_MAX, or SUB_UID_COUNT from /etc/login.defs.

       -w, --add-subgids FIRST-LAST
           Add a range of subordinate gids to the user's account.

           This option may be specified multiple times to add multiple ranges
           to a users account.

           No checks will be performed with regard to SUB_GID_MIN,
           SUB_GID_MAX, or SUB_GID_COUNT from /etc/login.defs.

       -W, --del-subgids FIRST-LAST
           Remove a range of subordinate gids from the user's account.

           This option may be specified multiple times to remove multiple
           ranges to a users account. When both --del-subgids and
           --add-subgids are specified, the removal of all subordinate gid
           ranges happens before any subordinate gid range is added.

           No checks will be performed with regard to SUB_GID_MIN,
           SUB_GID_MAX, or SUB_GID_COUNT from /etc/login.defs.

       -Z, --selinux-user SEUSER
           The new SELinux user for the user's login.

           A blank SEUSER will remove the SELinux user mapping for user LOGIN
           (if any).

CAVEATS
       You must make certain that the named user is not executing any
       processes when this command is being executed if the user's numerical
       user ID, the user's name, or the user's home directory is being
       changed.  usermod checks this on Linux. On other platforms it only uses
       utmp to check if the user is logged in.

       You must change the owner of any crontab files or at jobs manually.

       You must make any changes involving NIS on the NIS server.

CONFIGURATION
       The following configuration variables in /etc/login.defs change the
       behavior of this tool:

       MAIL_DIR (string)
           The mail spool directory. This is needed to manipulate the mailbox
           when its corresponding user account is modified or deleted. If not
           specified, a compile-time default is used.

       MAIL_FILE (string)
           Defines the location of the users mail spool files relatively to
           their home directory.

       The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and
       userdel to create, move, or delete the user's mail spool.

       If MAIL_CHECK_ENAB is set to yes, they are also used to define the MAIL
       environment variable.

       MAX_MEMBERS_PER_GROUP (number)
           Maximum members per group entry. When the maximum is reached, a new
           group entry (line) is started in /etc/group (with the same name,
           same password, and same GID).

           The default value is 0, meaning that there are no limits in the
           number of members in a group.

           This feature (split group) permits to limit the length of lines in
           the group file. This is useful to make sure that lines for NIS
           groups are not larger than 1024 characters.

           If you need to enforce such limit, you can use 25.

           Note: split groups may not be supported by all tools (even in the
           Shadow toolsuite). You should not use this variable unless you
           really need it.

       SUB_GID_MIN (number), SUB_GID_MAX (number), SUB_GID_COUNT (number)
           If /etc/subuid exists, the commands useradd and newusers (unless
           the user already have subordinate group IDs) allocate SUB_GID_COUNT
           unused group IDs from the range SUB_GID_MIN to SUB_GID_MAX for each
           new user.

           The default values for SUB_GID_MIN, SUB_GID_MAX, SUB_GID_COUNT are
           respectively 100000, 600100000 and 65536.

       SUB_UID_MIN (number), SUB_UID_MAX (number), SUB_UID_COUNT (number)
           If /etc/subuid exists, the commands useradd and newusers (unless
           the user already have subordinate user IDs) allocate SUB_UID_COUNT
           unused user IDs from the range SUB_UID_MIN to SUB_UID_MAX for each
           new user.

           The default values for SUB_UID_MIN, SUB_UID_MAX, SUB_UID_COUNT are
           respectively 100000, 600100000 and 65536.

FILES
       /etc/group
           Group account information.

       /etc/gshadow
           Secure group account information.

       /etc/login.defs
           Shadow password suite configuration.

       /etc/passwd
           User account information.

       /etc/shadow
           Secure user account information.

       /etc/subgid
           Per user subordinate group IDs.

       /etc/subuid
           Per user subordinate user IDs.

SEE ALSO
       chfn(1), chsh(1), passwd(1), crypt(3), gpasswd(8), groupadd(8),
       groupdel(8), groupmod(8), login.defs(5), subgid(5),
       subuid(5),useradd(8), userdel(8).



shadow-utils 4.6                  08/09/2019                        USERMOD(8)

---

III. 예제

다음 조건에 맞게 사용자를 정보를 변경하려고 한다.

예제 1

• yuloje 사용자의 로그인을 일시적으로 정지시킨다.
• posein 사용자는 2016년 12월 31일까지만 로그인이 되도록 설정하고, 패스워드 만기일이 지난 후 유예 기간은 5일로 설정한다.

# usermod -L yuloje
# usermod -e 2016-12-31 -f 5 posein

• -g : 그룹을 지정할 때 사용
• -d : 홈 디렉터리를 지정할 때 사용

예제 2

posein 사용자의 아이디를 yuloje로 변경하려고 한다.

• 홈 디렉터리는 기존의 /home/posein에서 /home/yuloje로 변경한다.
• 기존에 사용하던 파일이나 디렉터리들은 그대로 옮겨오도록 한다.
• 괄호에는 옵션 또는 옵션과 관련된 인자값을 적는데, 옵션과 관련된 인자값은 하나의 괄호로 처리한다. (예: -u posein)

# usermod -l yuloje -d /home/posein -m posein