1CHGPASSWD(8) System Management Commands CHGPASSWD(8)
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6 chgpasswd - update group passwords in batch mode
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9 chgpasswd [options]
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12 The chgpasswd command reads a list of group name and password pairs
13 from standard input and uses this information to update a set of
14 existing groups. Each line is of the format:
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16 group_name:password
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18 By default the supplied password must be in clear-text, and is
19 encrypted by chgpasswd.
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21 The default encryption algorithm can be defined for the system with the
22 ENCRYPT_METHOD variable of /etc/login.defs, and can be overwritten with
23 the -e, -m, or -c options.
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25 This command is intended to be used in a large system environment where
26 many accounts are created at a single time.
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29 The options which apply to the chgpasswd command are:
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31 -c, --crypt-method
32 Use the specified method to encrypt the passwords.
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34 The available methods are DES, MD5, NONE, and SHA256 or SHA512 if
35 your libc support these methods.
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37 -e, --encrypted
38 Supplied passwords are in encrypted form.
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40 -h, --help
41 Display help message and exit.
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43 -m, --md5
44 Use MD5 encryption instead of DES when the supplied passwords are
45 not encrypted.
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47 -R, --root CHROOT_DIR
48 Apply changes in the CHROOT_DIR directory and use the configuration
49 files from the CHROOT_DIR directory.
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51 -s, --sha-rounds
52 Use the specified number of rounds to encrypt the passwords.
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54 The value 0 means that the system will choose the default number of
55 rounds for the crypt method (5000).
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57 A minimal value of 1000 and a maximal value of 999,999,999 will be
58 enforced.
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60 You can only use this option with the SHA256 or SHA512 crypt
61 method.
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63 By default, the number of rounds is defined by the
64 SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in
65 /etc/login.defs.
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68 Remember to set permissions or umask to prevent readability of
69 unencrypted files by other users.
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71 You should make sure the passwords and the encryption method respect
72 the system's password policy.
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75 The following configuration variables in /etc/login.defs change the
76 behavior of this tool:
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78 ENCRYPT_METHOD (string)
79 This defines the system default encryption algorithm for encrypting
80 passwords (if no algorithm are specified on the command line).
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82 It can take one of these values: DES (default), MD5, SHA256,
83 SHA512. MD5 and DES should not be used for new hashes, see crypt(5)
84 for recommendations.
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86 Note: this parameter overrides the MD5_CRYPT_ENAB variable.
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88 MAX_MEMBERS_PER_GROUP (number)
89 Maximum members per group entry. When the maximum is reached, a new
90 group entry (line) is started in /etc/group (with the same name,
91 same password, and same GID).
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93 The default value is 0, meaning that there are no limits in the
94 number of members in a group.
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96 This feature (split group) permits to limit the length of lines in
97 the group file. This is useful to make sure that lines for NIS
98 groups are not larger than 1024 characters.
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100 If you need to enforce such limit, you can use 25.
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102 Note: split groups may not be supported by all tools (even in the
103 Shadow toolsuite). You should not use this variable unless you
104 really need it.
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106 MD5_CRYPT_ENAB (boolean)
107 Indicate if passwords must be encrypted using the MD5-based
108 algorithm. If set to yes, new passwords will be encrypted using the
109 MD5-based algorithm compatible with the one used by recent releases
110 of FreeBSD. It supports passwords of unlimited length and longer
111 salt strings. Set to no if you need to copy encrypted passwords to
112 other systems which don't understand the new algorithm. Default is
113 no.
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115 This variable is superseded by the ENCRYPT_METHOD variable or by
116 any command line option used to configure the encryption algorithm.
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118 This variable is deprecated. You should use ENCRYPT_METHOD.
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120 SHA_CRYPT_MIN_ROUNDS (number), SHA_CRYPT_MAX_ROUNDS (number)
121 When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines the
122 number of SHA rounds used by the encryption algorithm by default
123 (when the number of rounds is not specified on the command line).
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125 With a lot of rounds, it is more difficult to brute forcing the
126 password. But note also that more CPU resources will be needed to
127 authenticate users.
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129 If not specified, the libc will choose the default number of rounds
130 (5000), which is orders of magnitude too low for modern hardware.
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132 The values must be inside the 1000-999,999,999 range.
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134 If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS
135 values is set, then this value will be used.
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137 If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest value
138 will be used.
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141 /etc/group
142 Group account information.
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144 /etc/gshadow
145 Secure group account information.
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147 /etc/login.defs
148 Shadow password suite configuration.
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151 gpasswd(1), groupadd(8), login.defs(5).
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155shadow-utils 4.9 11/19/2021 CHGPASSWD(8)