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[Linux] 사용자 관리 명령어 정리

분류	명령어
사용자 생성	useradd	adduser	passwd	su
사용자 관련 파일	pwconv	pwunconv	pwck	useradd -D
사용자 계정 관리 및 삭제	usermod	userdel
사용자 패스워드 관리	passwd	chage	chpasswd
그룹 관리	grpconv	grpunconv	grpck	groupadd	groupmod	groupdel	gpasswd	newgrp
사용자 조회	users	who	whoami	w	logname	id	groups
기타	date	uname

useradd

사용자 계정을 추가해주는 명령어

$ useradd --help

 Usage: useradd [options] LOGIN
       useradd -D
       useradd -D [options]
 
Options:
  -b, --base-dir BASE_DIR       base directory for the home directory of the
                                new account
  -c, --comment COMMENT         GECOS field of the new account
  -d, --home-dir HOME_DIR       home directory of the new account
  -D, --defaults                print or change default useradd configuration
  -e, --expiredate EXPIRE_DATE  expiration date of the new account
  -f, --inactive INACTIVE       password inactivity period of the new account
  -g, --gid GROUP               name or ID of the primary group of the new
                                account
  -G, --groups GROUPS           list of supplementary groups of the new
                                account
  -h, --help                    display this help message and exit
  -k, --skel SKEL_DIR           use this alternative skeleton directory
  -K, --key KEY=VALUE           override /etc/login.defs defaults
  -l, --no-log-init             do not add the user to the lastlog and
                                faillog databases
  -m, --create-home             create the user's home directory
  -M, --no-create-home          do not create the user's home directory
  -N, --no-user-group           do not create a group with the same name as
                                the user
  -o, --non-unique              allow to create users with duplicate
                                (non-unique) UID
  -p, --password PASSWORD       encrypted password of the new account
  -r, --system                  create a system account
  -R, --root CHROOT_DIR         directory to chroot into
  -P, --prefix PREFIX_DIR       prefix directory where are located the /etc/* files
  -s, --shell SHELL             login shell of the new account
  -u, --uid UID                 user ID of the new account
  -U, --user-group              create a group with the same name as the user
  -Z, --selinux-user SEUSER     use a specific SEUSER for the SELinux user mapping

userdel

사용자 계정을 삭제해주는 명령어
-r 옵션을 사용하면, 사용자 홈 디렉터리 및 메일 관련 파일까지 제거할 수 있음.

$ userdel --help

 Usage: userdel [options] LOGIN
 
Options:
  -f, --force                   force some actions that would fail otherwise
                                e.g. removal of user still logged in
                                or files, even if not owned by the user
  -h, --help                    display this help message and exit
  -r, --remove                  remove home directory and mail spool
  -R, --root CHROOT_DIR         directory to chroot into
  -P, --prefix PREFIX_DIR       prefix directory where are located the /etc/* files
  -Z, --selinux-user            remove any SELinux user mapping for the user

usermod

사용자 계정 정보를 수정해주는 명령어

$ usermod --help

 Usage: usermod [options] LOGIN
 
Options:
  -c, --comment COMMENT         new value of the GECOS field
  -d, --home HOME_DIR           new home directory for the user account
  -e, --expiredate EXPIRE_DATE  set account expiration date to EXPIRE_DATE
  -f, --inactive INACTIVE       set password inactive after expiration
                                to INACTIVE
  -g, --gid GROUP               force use GROUP as new primary group
  -G, --groups GROUPS           new list of supplementary GROUPS
  -a, --append                  append the user to the supplemental GROUPS
                                mentioned by the -G option without removing
                                the user from other groups
  -h, --help                    display this help message and exit
  -l, --login NEW_LOGIN         new value of the login name
  -L, --lock                    lock the user account
  -m, --move-home               move contents of the home directory to the
                                new location (use only with -d)
  -o, --non-unique              allow using duplicate (non-unique) UID
  -p, --password PASSWORD       use encrypted password for the new password
  -R, --root CHROOT_DIR         directory to chroot into
  -P, --prefix PREFIX_DIR       prefix directory where are located the /etc/* files
  -s, --shell SHELL             new login shell for the user account
  -u, --uid UID                 new UID for the user account
  -U, --unlock                  unlock the user account
  -v, --add-subuids FIRST-LAST  add range of subordinate uids
  -V, --del-subuids FIRST-LAST  remove range of subordinate uids
  -w, --add-subgids FIRST-LAST  add range of subordinate gids
  -W, --del-subgids FIRST-LAST  remove range of subordinate gids
  -Z, --selinux-user SEUSER     new SELinux user mapping for the user account

passwd

사용자 계정의 암호를 설정해주는 명령어
다음의 경우에 사용
- 계정을 사용하지 못하게 하고 싶은 경우
- 패스워드 만기일 및 유효기간을 설정하고 싶은 경우

$ passwd --help

 Usage: passwd [OPTION...] <accountName>
  -k, --keep-tokens       keep non-expired authentication tokens
  -d, --delete            delete the password for the named account (root only)
  -l, --lock              lock the password for the named account (root only)
  -u, --unlock            unlock the password for the named account (root only)
  -e, --expire            expire the password for the named account (root only)
  -f, --force             force operation
  -x, --maximum=DAYS      maximum password lifetime (root only)
  -n, --minimum=DAYS      minimum password lifetime (root only)
  -w, --warning=DAYS      number of days warning users receives before password expiration (root only)
  -i, --inactive=DAYS     number of days after password expiration when an account becomes disabled (root
                          only)
  -S, --status            report password status on the named account (root only)
  --stdin                 read new tokens from stdin (root only)
 
Help options:
  -?, --help              Show this help message
  --usage                 Display brief usage message

chage

패스워드 만기일을 설정해주는 명령어
사용자의 패스워드에 대한 정보를 출력하고 설정

$ chage --help

 Usage: chage [options] LOGIN
 
Options:
  -d, --lastday LAST_DAY        set date of last password change to LAST_DAY
  -E, --expiredate EXPIRE_DATE  set account expiration date to EXPIRE_DATE
  -h, --help                    display this help message and exit
  -I, --inactive INACTIVE       set password inactive after expiration
                                to INACTIVE
  -l, --list                    show account aging information
  -m, --mindays MIN_DAYS        set minimum number of days before password
                                change to MIN_DAYS
  -M, --maxdays MAX_DAYS        set maximum number of days before password
                                change to MAX_DAYS
  -R, --root CHROOT_DIR         directory to chroot into
  -W, --warndays WARN_DAYS      set expiration warning days to WARN_DAYS

chpasswd

사용자의 패스워드를 변경하는 명령어
보통 여러 사용자들의 패스워드를 한꺼번에 변경할 때 사용함.

$ chpasswd --help

 Usage: chpasswd [options]
 
Options:
  -c, --crypt-method METHOD     the crypt method (one of NONE DES MD5 SHA256 SHA512)
  -e, --encrypted               supplied passwords are encrypted
  -h, --help                    display this help message and exit
  -m, --md5                     encrypt the clear text password using
                                the MD5 algorithm
  -R, --root CHROOT_DIR         directory to chroot into
  -s, --sha-rounds              number of SHA rounds for the SHA*
                                crypt algorithm

pwconv

/etc/shadow 파일을 생성해주는 명령어
사용자의 패스워드를 /etc/shadow 파일에서 관리함.

$ pwconv --help

 Usage: pwconv [options]
 
Options:
  -h, --help                    display this help message and exit
  -R, --root CHROOT_DIR         directory to chroot into

pwunconv

/etc/passwd 파일을 생성해주는 명령어
사용자의 패스워드를 /etc/passwd 파일에서 관리함.

$ pwunconv --help

 Usage: pwunconv [options]
 
Options:
  -h, --help                    display this help message and exit
  -R, --root CHROOT_DIR         directory to chroot into

pwck

사용자 관련 파일인 /etc/passwd와 /etc/shadow를 점검해주는 명령어
- 각 사용자의 필드 개수 검사
- 아이디 중복 여부 검사
- 유효한 사용자 여부 검사
- 유효한 UID 및 GID 여부 검사
- 사용자의 Primary 그룹 존재 여부 검사
- 홈 디렉터리 존재 유무 검사
- 로그인 셀 검사

$ pwck --help

 Usage: pwck [options] [passwd [shadow]]
 
Options:
  -h, --help                    display this help message and exit
  -q, --quiet                   report errors only
  -r, --read-only               display errors and warnings
                                but do not change files
  -R, --root CHROOT_DIR         directory to chroot into
  -s, --sort                    sort entries by UID

grpconv

/etc/gshadow 파일을 생성해주는 명령어
그룹의 패스워드를 /etc/gshadow 파일에서 관리함.

$ grpconv --help

 Usage: grpconv [options]
 
Options:
  -h, --help                    display this help message and exit
  -R, --root CHROOT_DIR         directory to chroot into

grpunconv

/etc/group 파일을 생성해주는 명령어
사용자의 패스워드를 /etc/group 파일에서 관리함.

$ grpunconv --help

 Usage: grpunconv [options]
 
Options:
  -h, --help                    display this help message and exit
  -R, --root CHROOT_DIR         directory to chroot into

grpck

사용자 관련 파일인 /etc/group 과 /etc/gshadow를 점검해주는 명령어
- 각 그룹의 필드 개수 검사
- 그룹 중복 여부 검사
- 유효한 그룹 여부 검사
- 유효한 GID 여부 검사
- 그룹 멤버와 관리자 검사

$ grpck --help

 Usage: grpck [options] [group [gshadow]]
 
Options:
  -h, --help                    display this help message and exit
  -r, --read-only               display errors and warnings
                                but do not change files
  -R, --root CHROOT_DIR         directory to chroot into
  -s, --sort                    sort entries by UID

groupadd

새로운 그룹을 생성해주는 명령어
root만 사용 가능

$ groupadd --help

 Usage: groupadd [options] GROUP
 
Options:
  -f, --force                   exit successfully if the group already exists,
                                and cancel -g if the GID is already used
  -g, --gid GID                 use GID for the new group
  -h, --help                    display this help message and exit
  -K, --key KEY=VALUE           override /etc/login.defs defaults
  -o, --non-unique              allow to create groups with duplicate
                                (non-unique) GID
  -p, --password PASSWORD       use this encrypted password for the new group
  -r, --system                  create a system account
  -R, --root CHROOT_DIR         directory to chroot into
  -P, --prefix PREFIX_DIR       directory prefix

groupmod

그룹의 설정을 변경해주는 명령어 (그룹명, GID 등)

$ groupmod --help

 Usage: groupmod [options] GROUP
 
Options:
  -g, --gid GID                 change the group ID to GID
  -h, --help                    display this help message and exit
  -n, --new-name NEW_GROUP      change the name to NEW_GROUP
  -o, --non-unique              allow to use a duplicate (non-unique) GID
  -p, --password PASSWORD       change the password to this (encrypted)
                                PASSWORD
  -R, --root CHROOT_DIR         directory to chroot into
  -P, --prefix PREFIX_DIR       prefix directory where are located the /etc/* files

groupdel

생성된 그룹을 삭제해주는 명령어
삭제할 그룹에 속한 사용자가 없어야 함.
- 2차 그룹(Secondary Group)으로 속한 사용자들은 존재해도 상관 없음.

$ groupdel --help

 Usage: groupdel [options] GROUP
 
Options:
  -h, --help                    display this help message and exit
  -R, --root CHROOT_DIR         directory to chroot into
  -P, --prefix PREFIX_DIR       prefix directory where are located the /etc/* files
  -f, --force                   delete group even if it is the primary group of a user

gpasswd

그룹의 암호를 설정하거나 그룹 관리를 수행해주는 명령어
다음의 목적을 수행함.
- 그룹의 패스워드 설정
- 그룹 관리자 지정

$ gpasswd --help

 Usage: gpasswd [option] GROUP
 
Options:
  -a, --add USER                add USER to GROUP
  -d, --delete USER             remove USER from GROUP
  -h, --help                    display this help message and exit
  -Q, --root CHROOT_DIR         directory to chroot into
  -r, --delete-password         remove the GROUP's password
  -R, --restrict                restrict access to GROUP to its members
  -M, --members USER,...        set the list of members of GROUP
  -A, --administrators ADMIN,...
                                set the list of administrators for GROUP
Except for the -A and -M options, the options cannot be combined.

newgrp

사용자가 일시적으로 1차 그룹을 변경할 때 사용하는 명령
해당 그룹에 소속된 경우에는 패스워드 입력 없이 가능함.
- 그룹 패스워드가 설정되어 있는 경우, 패스워드 입력 후에 그룹 전환이 가능함.
그룹 전환 후에 원래 그룹으로 돌아가려면 exit 라고 입력하면 됨.

$ newgrp --help

Usage: newgrp [-] [group]

chgrp

파일이나 디렉터리의 소유 그룹을 변경해주는 명령어

$ chgrp --help

 Usage: chgrp [OPTION]... GROUP FILE...
  or:  chgrp [OPTION]... --reference=RFILE FILE...
Change the group of each FILE to GROUP.
With --reference, change the group of each FILE to that of RFILE.
 
  -c, --changes          like verbose but report only when a change is made
  -f, --silent, --quiet  suppress most error messages
  -v, --verbose          output a diagnostic for every file processed
      --dereference      affect the referent of each symbolic link (this is
                         the default), rather than the symbolic link itself
  -h, --no-dereference   affect symbolic links instead of any referenced file
                         (useful only on systems that can change the
                         ownership of a symlink)
      --no-preserve-root  do not treat '/' specially (the default)
      --preserve-root    fail to operate recursively on '/'
      --reference=RFILE  use RFILE's group rather than specifying a
                         GROUP value
  -R, --recursive        operate on files and directories recursively
 
The following options modify how a hierarchy is traversed when the -R
option is also specified.  If more than one is specified, only the final
one takes effect.
 
  -H                     if a command line argument is a symbolic link
                         to a directory, traverse it
  -L                     traverse every symbolic link to a directory
                         encountered
  -P                     do not traverse any symbolic links (default)
 
      --help     display this help and exit
      --version  output version information and exit
 
Examples:
  chgrp staff /u      Change the group of /u to "staff".
  chgrp -hR staff /u  Change the group of /u and subfiles to "staff".
 
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
For complete documentation, run: info coreutils 'chgrp invocation'

chmod

파일이나 디렉터리의 허가권을 변경해주는 명령어

$ chmod --help

 Usage: chmod [OPTION]... MODE[,MODE]... FILE...
  or:  chmod [OPTION]... OCTAL-MODE FILE...
  or:  chmod [OPTION]... --reference=RFILE FILE...
Change the mode of each FILE to MODE.
With --reference, change the mode of each FILE to that of RFILE.
 
  -c, --changes          like verbose but report only when a change is made
  -f, --silent, --quiet  suppress most error messages
  -v, --verbose          output a diagnostic for every file processed
      --no-preserve-root  do not treat '/' specially (the default)
      --preserve-root    fail to operate recursively on '/'
      --reference=RFILE  use RFILE's mode instead of MODE values
  -R, --recursive        change files and directories recursively
      --help     display this help and exit
      --version  output version information and exit
 
Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.
 
GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
For complete documentation, run: info coreutils 'chmod invocation'

사용자 변환 명령어

$ su --help

 Usage:
 su [options] [-] [USER [arg]...]
 
Change the effective user id and group id to that of USER.
A mere - implies -l.   If USER not given, assume root.
 
Options:
 -m, -p, --preserve-environment  do not reset environment variables
 -g, --group <group>             specify the primary group
 -G, --supp-group <group>        specify a supplemental group
 
 -, -l, --login                  make the shell a login shell
 -c, --command <command>         pass a single command to the shell with -c
 --session-command <command>     pass a single command to the shell with -c
                                 and do not create a new session
 -f, --fast                      pass -f to the shell (for csh or tcsh)
 -s, --shell <shell>             run shell if /etc/shells allows it
 
 -h, --help     display this help and exit
 -V, --version  output version information and exit
 
For more details see su(1).

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[Linux] 사용자 관리 명령어 정리

[Linux] 사용자 관리 명령어 정리

useradd

userdel

usermod

passwd

chage

chpasswd

pwconv

pwunconv

pwck

grpconv

grpunconv

grpck

groupadd

groupmod

groupdel

gpasswd

newgrp

chmod

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모든 영역

	Usage: useradd [options] LOGIN
	useradd -D
	useradd -D [options]

	Options:
	-b, --base-dir BASE_DIR base directory for the home directory of the
	new account
	-c, --comment COMMENT GECOS field of the new account
	-d, --home-dir HOME_DIR home directory of the new account
	-D, --defaults print or change default useradd configuration
	-e, --expiredate EXPIRE_DATE expiration date of the new account
	-f, --inactive INACTIVE password inactivity period of the new account
	-g, --gid GROUP name or ID of the primary group of the new
	account
	-G, --groups GROUPS list of supplementary groups of the new
	account
	-h, --help display this help message and exit
	-k, --skel SKEL_DIR use this alternative skeleton directory
	-K, --key KEY=VALUE override /etc/login.defs defaults
	-l, --no-log-init do not add the user to the lastlog and
	faillog databases
	-m, --create-home create the user's home directory
	-M, --no-create-home do not create the user's home directory
	-N, --no-user-group do not create a group with the same name as
	the user
	-o, --non-unique allow to create users with duplicate
	(non-unique) UID
	-p, --password PASSWORD encrypted password of the new account
	-r, --system create a system account
	-R, --root CHROOT_DIR directory to chroot into
	-P, --prefix PREFIX_DIR prefix directory where are located the /etc/* files
	-s, --shell SHELL login shell of the new account
	-u, --uid UID user ID of the new account
	-U, --user-group create a group with the same name as the user
	-Z, --selinux-user SEUSER use a specific SEUSER for the SELinux user mapping

	Usage: userdel [options] LOGIN

	Options:
	-f, --force force some actions that would fail otherwise
	e.g. removal of user still logged in
	or files, even if not owned by the user
	-h, --help display this help message and exit
	-r, --remove remove home directory and mail spool
	-R, --root CHROOT_DIR directory to chroot into
	-P, --prefix PREFIX_DIR prefix directory where are located the /etc/* files
	-Z, --selinux-user remove any SELinux user mapping for the user

	Usage: usermod [options] LOGIN

	Options:
	-c, --comment COMMENT new value of the GECOS field
	-d, --home HOME_DIR new home directory for the user account
	-e, --expiredate EXPIRE_DATE set account expiration date to EXPIRE_DATE
	-f, --inactive INACTIVE set password inactive after expiration
	to INACTIVE
	-g, --gid GROUP force use GROUP as new primary group
	-G, --groups GROUPS new list of supplementary GROUPS
	-a, --append append the user to the supplemental GROUPS
	mentioned by the -G option without removing
	the user from other groups
	-h, --help display this help message and exit
	-l, --login NEW_LOGIN new value of the login name
	-L, --lock lock the user account
	-m, --move-home move contents of the home directory to the
	new location (use only with -d)
	-o, --non-unique allow using duplicate (non-unique) UID
	-p, --password PASSWORD use encrypted password for the new password
	-R, --root CHROOT_DIR directory to chroot into
	-P, --prefix PREFIX_DIR prefix directory where are located the /etc/* files
	-s, --shell SHELL new login shell for the user account
	-u, --uid UID new UID for the user account
	-U, --unlock unlock the user account
	-v, --add-subuids FIRST-LAST add range of subordinate uids
	-V, --del-subuids FIRST-LAST remove range of subordinate uids
	-w, --add-subgids FIRST-LAST add range of subordinate gids
	-W, --del-subgids FIRST-LAST remove range of subordinate gids
	-Z, --selinux-user SEUSER new SELinux user mapping for the user account

	Usage: passwd [OPTION...] <accountName>
	-k, --keep-tokens keep non-expired authentication tokens
	-d, --delete delete the password for the named account (root only)
	-l, --lock lock the password for the named account (root only)
	-u, --unlock unlock the password for the named account (root only)
	-e, --expire expire the password for the named account (root only)
	-f, --force force operation
	-x, --maximum=DAYS maximum password lifetime (root only)
	-n, --minimum=DAYS minimum password lifetime (root only)
	-w, --warning=DAYS number of days warning users receives before password expiration (root only)
	-i, --inactive=DAYS number of days after password expiration when an account becomes disabled (root
	only)
	-S, --status report password status on the named account (root only)
	--stdin read new tokens from stdin (root only)

	Help options:
	-?, --help Show this help message
	--usage Display brief usage message

	Usage: chage [options] LOGIN

	Options:
	-d, --lastday LAST_DAY set date of last password change to LAST_DAY
	-E, --expiredate EXPIRE_DATE set account expiration date to EXPIRE_DATE
	-h, --help display this help message and exit
	-I, --inactive INACTIVE set password inactive after expiration
	to INACTIVE
	-l, --list show account aging information
	-m, --mindays MIN_DAYS set minimum number of days before password
	change to MIN_DAYS
	-M, --maxdays MAX_DAYS set maximum number of days before password
	change to MAX_DAYS
	-R, --root CHROOT_DIR directory to chroot into
	-W, --warndays WARN_DAYS set expiration warning days to WARN_DAYS

	Usage: chpasswd [options]

	Options:
	-c, --crypt-method METHOD the crypt method (one of NONE DES MD5 SHA256 SHA512)
	-e, --encrypted supplied passwords are encrypted
	-h, --help display this help message and exit
	-m, --md5 encrypt the clear text password using
	the MD5 algorithm
	-R, --root CHROOT_DIR directory to chroot into
	-s, --sha-rounds number of SHA rounds for the SHA*
	crypt algorithm

	Usage: pwconv [options]

	Options:
	-h, --help display this help message and exit
	-R, --root CHROOT_DIR directory to chroot into

	Usage: pwunconv [options]

	Options:
	-h, --help display this help message and exit
	-R, --root CHROOT_DIR directory to chroot into

	Usage: pwck [options] [passwd [shadow]]

	Options:
	-h, --help display this help message and exit
	-q, --quiet report errors only
	-r, --read-only display errors and warnings
	but do not change files
	-R, --root CHROOT_DIR directory to chroot into
	-s, --sort sort entries by UID

	Usage: grpconv [options]

	Options:
	-h, --help display this help message and exit
	-R, --root CHROOT_DIR directory to chroot into

	Usage: grpunconv [options]

	Options:
	-h, --help display this help message and exit
	-R, --root CHROOT_DIR directory to chroot into

	Usage: grpck [options] [group [gshadow]]

	Options:
	-h, --help display this help message and exit
	-r, --read-only display errors and warnings
	but do not change files
	-R, --root CHROOT_DIR directory to chroot into
	-s, --sort sort entries by UID

	Usage: groupadd [options] GROUP

	Options:
	-f, --force exit successfully if the group already exists,
	and cancel -g if the GID is already used
	-g, --gid GID use GID for the new group
	-h, --help display this help message and exit
	-K, --key KEY=VALUE override /etc/login.defs defaults
	-o, --non-unique allow to create groups with duplicate
	(non-unique) GID
	-p, --password PASSWORD use this encrypted password for the new group
	-r, --system create a system account
	-R, --root CHROOT_DIR directory to chroot into
	-P, --prefix PREFIX_DIR directory prefix

	Usage: groupmod [options] GROUP

	Options:
	-g, --gid GID change the group ID to GID
	-h, --help display this help message and exit
	-n, --new-name NEW_GROUP change the name to NEW_GROUP
	-o, --non-unique allow to use a duplicate (non-unique) GID
	-p, --password PASSWORD change the password to this (encrypted)
	PASSWORD
	-R, --root CHROOT_DIR directory to chroot into
	-P, --prefix PREFIX_DIR prefix directory where are located the /etc/* files

	Usage: groupdel [options] GROUP

	Options:
	-h, --help display this help message and exit
	-R, --root CHROOT_DIR directory to chroot into
	-P, --prefix PREFIX_DIR prefix directory where are located the /etc/* files
	-f, --force delete group even if it is the primary group of a user

	Usage: gpasswd [option] GROUP

	Options:
	-a, --add USER add USER to GROUP
	-d, --delete USER remove USER from GROUP
	-h, --help display this help message and exit
	-Q, --root CHROOT_DIR directory to chroot into
	-r, --delete-password remove the GROUP's password
	-R, --restrict restrict access to GROUP to its members
	-M, --members USER,... set the list of members of GROUP
	-A, --administrators ADMIN,...
	set the list of administrators for GROUP
	Except for the -A and -M options, the options cannot be combined.

	Usage: chgrp [OPTION]... GROUP FILE...
	or: chgrp [OPTION]... --reference=RFILE FILE...
	Change the group of each FILE to GROUP.
	With --reference, change the group of each FILE to that of RFILE.

	-c, --changes like verbose but report only when a change is made
	-f, --silent, --quiet suppress most error messages
	-v, --verbose output a diagnostic for every file processed
	--dereference affect the referent of each symbolic link (this is
	the default), rather than the symbolic link itself
	-h, --no-dereference affect symbolic links instead of any referenced file
	(useful only on systems that can change the
	ownership of a symlink)
	--no-preserve-root do not treat '/' specially (the default)
	--preserve-root fail to operate recursively on '/'
	--reference=RFILE use RFILE's group rather than specifying a
	GROUP value
	-R, --recursive operate on files and directories recursively

	The following options modify how a hierarchy is traversed when the -R
	option is also specified. If more than one is specified, only the final
	one takes effect.

	-H if a command line argument is a symbolic link
	to a directory, traverse it
	-L traverse every symbolic link to a directory
	encountered
	-P do not traverse any symbolic links (default)

	--help display this help and exit
	--version output version information and exit

	Examples:
	chgrp staff /u Change the group of /u to "staff".
	chgrp -hR staff /u Change the group of /u and subfiles to "staff".

	GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
	For complete documentation, run: info coreutils 'chgrp invocation'

	Usage: chmod [OPTION]... MODE[,MODE]... FILE...
	or: chmod [OPTION]... OCTAL-MODE FILE...
	or: chmod [OPTION]... --reference=RFILE FILE...
	Change the mode of each FILE to MODE.
	With --reference, change the mode of each FILE to that of RFILE.

	-c, --changes like verbose but report only when a change is made
	-f, --silent, --quiet suppress most error messages
	-v, --verbose output a diagnostic for every file processed
	--no-preserve-root do not treat '/' specially (the default)
	--preserve-root fail to operate recursively on '/'
	--reference=RFILE use RFILE's mode instead of MODE values
	-R, --recursive change files and directories recursively
	--help display this help and exit
	--version output version information and exit

	Each MODE is of the form '[ugoa]([-+=]([rwxXst]\|[ugo]))+\|[-+=][0-7]+'.

	GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
	For complete documentation, run: info coreutils 'chmod invocation'

	Usage:
	su [options] [-] [USER [arg]...]

	Change the effective user id and group id to that of USER.
	A mere - implies -l. If USER not given, assume root.

	Options:
	-m, -p, --preserve-environment do not reset environment variables
	-g, --group <group> specify the primary group
	-G, --supp-group <group> specify a supplemental group

	-, -l, --login make the shell a login shell
	-c, --command <command> pass a single command to the shell with -c
	--session-command <command> pass a single command to the shell with -c
	and do not create a new session
	-f, --fast pass -f to the shell (for csh or tcsh)
	-s, --shell <shell> run shell if /etc/shells allows it

	-h, --help display this help and exit
	-V, --version output version information and exit

	For more details see su(1).