1PWCK(8) System Management Commands PWCK(8)
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6 pwck - verify the integrity of password files
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9 pwck [options] [PASSWORDFILE [ SHADOWFILE ]]
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12 The pwck command verifies the integrity of the users and authentication
13 information. It checks that all entries in /etc/passwd and /etc/shadow
14 have the proper format and contain valid data. The user is prompted to
15 delete entries that are improperly formatted or which have other
16 uncorrectable errors.
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18 Checks are made to verify that each entry has:
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20 • the correct number of fields
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22 • a unique and valid user name
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24 • a valid user and group identifier
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26 • a valid primary group
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28 • a valid home directory
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30 • a valid login shell
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32 Checks for shadowed password information are enabled when the second
33 file parameter SHADOWFILE is specified or when /etc/shadow exists on
34 the system.
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36 These checks are the following:
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38 • every passwd entry has a matching shadow entry, and every shadow
39 entry has a matching passwd entry
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41 • passwords are specified in the shadowed file
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43 • shadow entries have the correct number of fields
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45 • shadow entries are unique in shadow
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47 • the last password changes are not in the future
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49 The checks for correct number of fields and unique user name are fatal.
50 If the entry has the wrong number of fields, the user will be prompted
51 to delete the entire line. If the user does not answer affirmatively,
52 all further checks are bypassed. An entry with a duplicated user name
53 is prompted for deletion, but the remaining checks will still be made.
54 All other errors are warnings and the user is encouraged to run the
55 usermod command to correct the error.
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57 The commands which operate on the /etc/passwd file are not able to
58 alter corrupted or duplicated entries. pwck should be used in those
59 circumstances to remove the offending entry.
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62 The -r and -s options cannot be combined.
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64 The options which apply to the pwck command are:
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66 --badname
67 Allow names that do not conform to standards.
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69 -h, --help
70 Display help message and exit.
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72 -q, --quiet
73 Report errors only. The warnings which do not require any action
74 from the user won't be displayed.
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76 -r, --read-only
77 Execute the pwck command in read-only mode.
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79 -R, --root CHROOT_DIR
80 Apply changes in the CHROOT_DIR directory and use the configuration
81 files from the CHROOT_DIR directory. Only absolute paths are
82 supported.
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84 -s, --sort
85 Sort entries in /etc/passwd and /etc/shadow by UID.
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87 By default, pwck operates on the files /etc/passwd and /etc/shadow. The
88 user may select alternate files with the passwd and shadow parameters.
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91 The following configuration variables in /etc/login.defs change the
92 behavior of this tool:
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94 NONEXISTENT (string)
95 If a system account intentionally does not have a home directory
96 that exists, this string can be provided in the /etc/passwd entry
97 for the account to indicate this. The result is that pwck will not
98 emit a spurious warning for this account.
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100 PASS_MAX_DAYS (number)
101 The maximum number of days a password may be used. If the password
102 is older than this, a password change will be forced. If not
103 specified, -1 will be assumed (which disables the restriction).
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105 PASS_MIN_DAYS (number)
106 The minimum number of days allowed between password changes. Any
107 password changes attempted sooner than this will be rejected. If
108 not specified, 0 will be assumed (which disables the restriction).
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110 PASS_WARN_AGE (number)
111 The number of days warning given before a password expires. A zero
112 means warning is given only upon the day of expiration, a negative
113 value means no warning is given. If not specified, no warning will
114 be provided.
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117 /etc/group
118 Group account information.
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120 /etc/passwd
121 User account information.
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123 /etc/shadow
124 Secure user account information.
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127 The pwck command exits with the following values:
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129 0
130 success
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132 1
133 invalid command syntax
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135 2
136 one or more bad password entries
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138 3
139 can't open password files
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141 4
142 can't lock password files
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144 5
145 can't update password files
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148 can't sort password files
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151 group(5), grpck(8), passwd(5), shadow(5), usermod(8).
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155shadow-utils 4.12.3 11/29/2022 PWCK(8)