大家应该都知道，在Linux系统中，1000以下的UID是系统保留的UID。随意修改系统上某些帐号的 UID 很可能会导致某些程序无法进行，甚至导致系统无法顺利运行。我们可以通过/usr/share/doc/setup-2.8.71/uidgid来查看具体对应关系，当然不同的版本路径可能不一样，可以用/usr/share/doc/setup*/uidgid来通配。

NAME    UID GID HOME        SHELL   PACKAGESroot    0   0   /root       /bin/bash   setupbin 1   1   /bin        /sbin/nologin   setupdaemon  2   2   /sbin       /sbin/nologin   setupsys -   3   -       -   setupadm 3   4   /var/adm        /bin/bash   setuptty -   5   -       -   setupdisk    -   6   -       -   setuplp  4   7   /var/spool/lpd      /sbin/nologin   setupmem -   8   -       -   setupkmem    -   9   -       -   setupwheel   -   10  -       -   setupcdrom   -   11  -       -   setupsync    5   (0) /sbin       /bin/sync   setupshutdown    6   (0) /sbin       /sbin/shutdown  setuphalt    7   (0) /sbin       /sbin/halt  setupmail    8   12  /var/spool/mail     /sbin/nologin   setupnews    9   13  /var/spool/news     /sbin/nologin   setupuucp    10  14  /var/spool/uucp     /sbin/nologin   uucpoperator    11  (0) /root       /sbin/nologin   setupgames   12  (100)   /usr/games      /sbin/nologin   setupgopher  13  30  /var/gopher     /sbin/nologin   -(not created by default)ftp 14  50  /var/ftp        /sbin/nologin   setupman -   15  -       -   setupoprofile    16  16  /var/lib/oprofile       /sbin/nologin   oprofilepkiuser 17  17  /usr/share/pki      /sbin/nologin   pki-ca,rhpki-cadialout -   18  -       -   setupfloppy  -   19  -       -   setupgames   -   20  -       -   setupslocate -   21  -       -   slocateutmp    -   22  -       -   initscripts,libutemptersquid   23  23  /var/spool/squid        /dev/null   squidpvm 24  24  /usr/share/pvm3     /bin/bash   pvmnamed   25  25  /var/named      /bin/false  bindpostgres    26  26  /var/lib/pgsql      /bin/bash   postgresql-servermysql   27  27  /var/lib/mysql      /bin/bash   mysqlnscd    28  28  /       /bin/false  nscdrpcuser 29  29  /var/lib/nfs        /bin/false  nfs-utilsconsole -   31  -       -   devrpc 32  32  /       /bin/false  portmapamandabackup    33  (6) /var/lib/amanda     /bin/false  amandatape    -   33  -       -   setupnetdump 34  34  /var/crash      /bin/bash   netdump-client, netdump-serverutempter    -   35  -       -   libutemptervdsm    36  -   /       /bin/bash   kvm, vdsmkvm -   36  -       -   kvm, vdsm, libvirtrpm 37  37  /var/lib/rpm        /bin/bash   rpmntp 38  38  /etc/ntp        /sbin/nologin   ntpvideo   -   39  -       -   setupdip -   40  -       -   pppmailman 41  41  /var/mailman        /bin/false  mailmangdm 42  42  /var/gdm        /bin/bash   gdmxfs 43  43  /etc/X11/fs     /bin/false  XFree86-xfspppusers    -   44  -       -   linuxconfpopusers    -   45  -       -   linuxconfslipusers   -   46  -       -   linuxconfmailnull    47  47  /var/spool/mqueue       /dev/null   sendmailapache  48  48  /var/www        /bin/false  apachewnn 49  49  /home/wnn       /bin/bash   FreeWnnsmmsp   51  51  /var/spool/mqueue       /dev/null   sendmailpuppet  52  52  /var/lib/puppet     /sbin/nologin   puppettomcat  53  53  /var/lib/tomcat     /sbin/nologin   tomcatlock    -   54  -       -   lockdevldap    55  55  /var/lib/ldap       /bin/false  openldap-serversfrontpage   56  56  /var/www        /bin/false  mod_frontpagenut 57  57  /var/lib/ups        /bin/false  nutbeagleindex 58  58  /var/cache/beagle       /bin/false  beagletss 59  59  -       /sbin/nologin   trouserspiranha 60  60  /etc/sysconfig/ha       /dev/null   piranhaprelude-manager 61  61  -       /sbin/nologin   prelude-managersnortd  62  62  -       /sbin/nologin   snortdaudio   -   63  -       -   setupcondor  64  64  /var/lib/condor     /sbin/nologin   condordnslcd   65  (55)    /       /sbin/nologin   nslcdwine    -   66  -       -   winepegasus 66  65  /var/lib/Pegasus        /sbin/nologin   tog-pegasuswebalizer   67  67  /var/www/html/usage     /sbin/nologin   webalizerhaldaemon   68  68  /       /sbin/nologin   halvcsa    69  69  -       /sbin/nologin   dev,MAKEDEVavahi   70  70  /var/run/avahi-daemon       /sbin/nologin   avahirealtime    -   71  -       -   -tcpdump 72  72  /       /sbin/nologin   tcpdumpprivoxy 73  73  /etc/privoxy        /bin/bash   privoxysshd    74  74  /var/empty/sshd     /sbin/nologin   openssh-serverradvd   75  75  /       /bin/false  radvdcyrus   76  (12)    /var/imap       /bin/bash   cyrus-imapdsaslauth    -   76  -       -   cyrus-imapdarpwatch    77  77  /var/lib/arpwatch       /sbin/nologin   arpwatchfax 78  78  /var/spool/fax      /sbin/nologin   mgettynocpulse    79  79  /etc/sysconfig/nocpulse     /bin/bash   nocpulsedesktop 80  80  -       /sbin/nologin   desktop-file-utilsdbus    81  81  /       /sbin/nologin   dbusjonas   82  82  /var/lib/jonas      /sbin/nologin   jonasclamav  83  83  /tmp        /sbin/nologin   clamavscreen  -   84  -       -   screenquaggavt    -   85  -       -   quaggasabayon 86  86  -       /sbin/nologin   sabayonpolkituser  87  87  /       /sbin/nologin   PolicyKitwbpriv  -   88  -       -   samba-commonpostfix 89  89  /var/spool/postfix      /bin/true   postfixpostdrop    -   90  -       -   postfixmajordomo   91  91  /usr/lib/majordomo      /bin/bash   majordomoquagga  92  92  /       /sbin/nologin   quaggaexim    93  93  /var/spool/exim     /sbin/nologin   eximdistcache   94  94  /       /sbin/nologin   distcacheradiusd 95  95  /       /bin/false  freeradiushsqldb  96  96  /var/lib/hsqldb     /sbin/nologin   hsqldbdovecot 97  97  /usr/libexec/dovecot        /sbin/nologin   dovecotident   98  98  /       /sbin/nologin   identnobody  99  99  /       /sbin/nologin   setupusers   -   100 -       -   setupqemu    107 107 /       /sbin/nologin   libvirtovirt   108 108 /       /sbin/nologin   libvirtrhevm   109 109 /home/rhevm     /sbin/nologin   vdsm-regjetty   110 110 /usr/share/jetty        /sbin/nologin   jettysaned   111 111 /       /sbin/nologin   sane-backendsvhostmd 112 112 /usr/share/vhostmd      /sbin/nologin   vhostmdusbmuxd 113 113 /       /sbin/nologin   usbmuxdbacula  133 133 /var/spool/bacula       /sbin/nologin   baculacimsrvr 134 134 /       /sbin/nologin   tog-pegasus-libsmock    -   135 /       -   mockricci   140 140 /var/lib/ricci      /sbin/nologin   ricciluci    141 141 /var/lib/luci       /sbin/nologin   luciactivemq    142 142 /usr/share/activemq     /sbin/nologin   activemqstap-server 155 155 /var/lib/stap-server        /sbin/nologin   systemtapstapusr -   156 /       -   systemtap-runtimestapsys -   157 /       -   systemtap-runtimestapdev -   158 /       -   systemtap-runtimeswift   160 160 /var/lib/swift      /sbin/nologin   openstack-swiftglance  161 161 /var/lib/glance     /sbin/nologin   openstack-glancenova    162 162 /var/lib/nova       /sbin/nologin   openstack-novakeystone    163 163 /var/lib/keystone       /sbin/nologin   openstack-keystonequantum 164 164 /var/lib/quantum        /sbin/nologin   openstack-quantumcinder  165 165 /var/lib/cinder     /sbin/nologin   openstack-cinderceilometer  166 166 /var/lib/ceilometer     /sbin/nologin   openstack-ceilometerceph    167 167 /var/lib/ceph       /sbin/nologin   ceph-commonavahi-autoipd   170 170 /var/lib/avahi-autoipd      /sbin/nologin   avahipulse   171 171 /var/run/pulse      /sbin/nologin   pulseaudiortkit   172 172 /proc       /sbin/nologin   rtkitabrt    173 173 /etc/abrt       /sbin/nologin   abrtretrace 174 174 /usr/share/retrace-server       /sbin/nologin   retrace-serverovirtagent  175 175 /       /sbin/nologin   ovirt-guest-agentats 176 176 /       /sbin/nologin   trafficserverdhcpd   177 177 /       /sbin/nologin   dhcpmyproxy 178 178 /var/lib/myproxy        /sbin/nologin   myproxy-serversanlock 179 179 /var/run/sanlock        /sbin/nologin   sanlockaeolus  180 180 /var/aeolus     /sbin/nologin   aeolus-configurewallaby 181 181 /var/lib/wallaby        /sbin/nologin   wallabykatello 182 182 /usr/share/katello      /sbin/nologin   katello-commonelasticsearch   183 183 /usr/share/java/elasticsearch       /sbin/nologin   elasticsearchmongodb 184 184 /var/lib/mongodb        /sbin/nologin   mongodbjboss   185 185 /var/lib/jbossas        /sbin/nologin   jbossas-core    #was jboss-as and wildflyjbosson-agent   186 -   /       /sbin/nologin   jboss-on-agentjbosson -   186 -       -   jboss-on-agentheat    187 187 /var/lib/heat       /sbin/nologin   heathaproxy 188 188 /var/lib/haproxy        /sbin/nologin   haproxyhacluster   189 -   /       /sbin/nologin   pacemakerhaclient    -   189 -       -   pacemakersystemd-journal -   190 -       -   systemdsystemd-journal-gateway 191 191 /       /sbin/nologin   systemd#systemd-journal-gateway dynamic on new systems (may have different uid/gid)systemd-network 192 192 /       /sbin/nologin   systemdsystemd-resolve 193 193 /       /sbin/nologin   systemdgnats   ?   ?   ?       ?   gnats, gnats-dblistar  ?   ?   ?       ?   listarnfsnobody   65534   65534   /var/lib/nfs        /sbin/nologin   nfs-utils# Note: nfsnobody is 4294967294 on 64-bit platforms (-2)

在未来，系统保留UID值范围可能会扩大。现在在RHEL7官方文档中，已经推荐使用5000作为新建账户的最小UID值，怎么样来修改创建账号是最小UID，GID起始值及一些其他设置呢？

#邮件选项# *REQUIRED*#   Directory where mailboxes reside, _or_ name of file, relative to the#   home directory.  If you _do_ define both, MAIL_DIR takes precedence.#   QMAIL_DIR is for Qmail##QMAIL_DIR  MaildirMAIL_DIR    /var/spool/mail#MAIL_FILE  .mail#密码控制策略# Password aging controls:##   PASS_MAX_DAYS   Maximum number of days a password may be used.#   PASS_MIN_DAYS   Minimum number of days allowed between password changes.#   PASS_MIN_LEN    Minimum acceptable password length.#   PASS_WARN_AGE   Number of days warning given before a password expires.#PASS_MAX_DAYS   99999PASS_MIN_DAYS   0PASS_MIN_LEN    5PASS_WARN_AGE   7#UID起止范围设置，此处最小值被我修改为5000，最大值为60000.## Min/max values for automatic uid selection in useradd#UID_MIN                  5000UID_MAX                 60000# System accountsSYS_UID_MIN               201SYS_UID_MAX               999#GID起止范围设置，此处最小值被我修改为5000，最大值为60000.## Min/max values for automatic gid selection in groupadd#GID_MIN                  5000GID_MAX                 60000# System accountsSYS_GID_MIN               201SYS_GID_MAX               999#删除用户选项## If defined, this command is run when removing a user.# It should remove any at/cron/print jobs etc. owned by# the user to be removed (passed as the first argument).##USERDEL_CMD    /usr/sbin/userdel_local#是否创建用户目录## If useradd should create home directories for users by default# On RH systems, we do. This option is overridden with the -m flag on# useradd command line.#CREATE_HOME yes#umask设置# The permission mask is initialized to this value. If not specified, # the permission mask will be initialized to 022.UMASK           077#移除用户同时移除该用户原来所在除了原用户之外没有其他没有成员的组。# This enables userdel to remove user groups if no members exist.#USERGROUPS_ENAB yes# Use SHA512 to encrypt password.

这个配置文件简洁直观，只需要按照自己的需要修改即可。不作过多解释。