[root@localhost nginx-1.10.1]# tar --help
Usage: tar [OPTION...] [FILE]...
GNU `tar' saves many files together into a single tape or disk archive, and can
restore individual files from the archive.

Examples:
  tar -cf archive.tar foo bar  # Create archive.tar from files foo and bar.
  tar -tvf archive.tar         # List all files in archive.tar verbosely.
  tar -xf archive.tar          # Extract all files from archive.tar.

 Main operation mode:

  -A, --catenate, --concatenate   append tar files to an archive
  -c, --create               create a new archive
  -d, --diff, --compare      find differences between archive and file system
      --delete               delete from the archive (not on mag tapes!)
  -r, --append               append files to the end of an archive
  -t, --list                 list the contents of an archive
  -u, --update               only append files newer than copy in archive
  -x, --extract, --get       extract files from an archive

 Operation modifiers:

  -g, --listed-incremental=FILE   handle new GNU-format incremental backup
  -G, --incremental          handle old GNU-format incremental backup
      --ignore-failed-read   do not exit with nonzero on unreadable files
  -k, --keep-old-files       don't replace existing files when extracting
      --keep-newer-files     don't replace existing files that are newer than
                             their archive copies
      --no-overwrite-dir     preserve metadata of existing directories
  -n, --seek                 Archive is seekable
      --occurrence[=NUMBER]  process only the NUMth occurrence of each file in
                             the archive. This option is valid only in
                             conjunction with one of the subcommands --delete,
                             --diff, --extract or --list and when a list of
                             files is given either on the command line or via
                             -T option. NUMBER defaults to 1.
      --overwrite            overwrite existing files when extracting
  -O, --to-stdout            extract files to standard output
      --recursive-unlink     empty hierarchies prior to extracting directory
      --remove-files         remove files after adding them to the archive
  -S, --sparse               handle sparse files efficiently
  -U, --unlink-first         remove each file prior to extracting over it
  -W, --verify               attempt to verify the archive after writing it

 Handling of file attributes:

      --acls                 Save the ACLs to the archive
      --atime-preserve       don't change access times on dumped files
      --group=NAME           force NAME as group for added files
      --mode=CHANGES         force (symbolic) mode CHANGES for added files
  -m, --touch                don't extract file modified time
      --no-acls              Don't extract the ACLs from the archive
      --no-same-owner        extract files as yourself
      --no-same-permissions  do not extract permissions information
      --no-selinux           Don't extract the SELinux context from the archive

      --no-xattrs            Don't extract the user/root xattrs from the
                             archive
      --numeric-owner        always use numbers for user/group names
      --owner=NAME           force NAME as owner for added files
  -p, --preserve-permissions, --same-permissions
                             extract permissions information
      --preserve             same as both -p and -s
      --same-owner           try extracting files with the same ownership
  -s, --preserve-order, --same-order
                             sort names to extract to match archive
      --selinux              Save the SELinux context to the archive
      --xattrs               Save the user/root xattrs to the archive

 Device selection and switching:

  -f, --file=ARCHIVE         use archive file or device ARCHIVE
      --force-local          archive file is local even if has a colon
  -F, --info-script=NAME, --new-volume-script=NAME
                             run script at end of each tape (implies -M)
  -L, --tape-length=NUMBER   change tape after writing NUMBER x 1024 bytes
  -M, --multi-volume         create/list/extract multi-volume archive
      --rmt-command=COMMAND  use given rmt COMMAND instead of rmt
      --rsh-command=COMMAND  use remote COMMAND instead of rsh
      --volno-file=FILE      use/update the volume number in FILE

 Device blocking:

  -b, --blocking-factor=BLOCKS   BLOCKS x 512 bytes per record
  -B, --read-full-records    reblock as we read (for 4.2BSD pipes)
  -i, --ignore-zeros         ignore zeroed blocks in archive (means EOF)
      --record-size=NUMBER   SIZE bytes per record, multiple of 512

 Archive format selection:

  -H, --format=FORMAT        create archive of the given format.

 FORMAT is one of the following:

    gnu                      GNU tar 1.13.x format
    oldgnu                   GNU format as per tar <= 1.12
    pax                      POSIX 1003.1-2001 (pax) format
    posix                    Same as pax
    ustar                    POSIX 1003.1-1988 (ustar) format
    v7                       old V7 tar format

  -j, --bzip2                filter the archive through bzip2
      --old-archive, --portability
                             same as --format=v7
      --pax-option=keyword[[:]=value][,keyword[[:]=value], ...]
                             control pax keywords
      --posix                same as --format=posix
      --use-compress-program=PROG
                             filter through PROG (must accept -d)
  -V, --label=TEXT           create archive with volume name NAME. At
                             list/extract time, use TEXT as a globbing pattern
  -z, --gzip, --gunzip, --ungzip   filter the archive through gzip
  -Z, --compress, --uncompress   filter the archive through compress

 Local file selection:

      --after-date=DATE      same as -N
      --anchored             exclude patterns match file name start
      --backup[=CONTROL]     backup before removal, choose version CONTROL
  -C, --directory=DIR        change to directory DIR
      --exclude=PATTERN      exclude files, given as a PATTERN
      --exclude-caches       exclude directories containing a cache tag
  -h, --dereference          dump instead the files symlinks point to
      --ignore-case          exclusion ignores case
  -K, --starting-file=MEMBER-NAME
                             begin at member MEMBER-NAME in the archive
      --newer-mtime=DATE     compare date and time when data changed only
      --no-anchored          exclude patterns match after any / (default)
      --no-ignore-case       exclusion is case sensitive (default)
      --no-recursion         avoid descending automatically in directories
      --no-wildcards         exclude patterns are plain strings
      --no-wildcards-match-slash   exclude pattern wildcards do not match '/'
      --null                 -T reads null-terminated names, disable -C
  -N, --newer=DATE-OR-FILE   only store files newer than DATE-OR-FILE
      --one-file-system      stay in local file system when creating archive
  -P, --absolute-names       don't strip leading `/'s from file names
      --recursion            recurse into directories (default)
      --strip-components=NUMBER   strip NUMBER leading components from file
                             names
      --suffix=STRING        backup before removal, override usual suffix ('~'
                             unless overridden by environment variable
                             SIMPLE_BACKUP_SUFFIX
  -T, --files-from=FILE-OF-NAMES   get names to extract or create from file
                             NAME
      --wildcards            exclude patterns use wildcards (default)
      --wildcards-match-slash   exclude pattern wildcards match '/' (default)
  -X, --exclude-from=FILE    exclude patterns listed in FILE

 Informative output:

      --checkpoint           display progress messages every 10th record
  -v, --verbose              verbosely list files processed

      --check-links          print a message if not all links are dumped
      --index-file=FILE      send verbose output to FILE
  -R, --block-number         show block number within archive with each
                             message
      --show-defaults        Show tar defaults
      --show-omitted-dirs    When listing or extracting, list each directory
                             that does not match search criteria
      --totals               print total bytes written while creating archive
      --utc                  print file modification dates in UTC
  -w, --interactive, --confirmation
                             ask for confirmation for every action

 Compatibility options:

      --allow-name-mangling  when creating, allow GNUTYPE_NAMES mangling --
                             considered dangerous
  -o                         when creating, same as --old-archive. When
                             extracting, same as --no-same-owner

 Other options:

  -?, --help                 Give this help list
      --license              Print license and exit
      --usage                Give a short usage message
      --version              Print program version

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.

The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.
The version control may be set with --backup or VERSION_CONTROL, values are:

  t, numbered     make numbered backups
  nil, existing   numbered if numbered backups exist, simple otherwise
  never, simple   always make simple backups

*This* tar defaults to:
--format=gnu -f- -b20 --rmt-command=/sbin/rmt --rsh-command=/usr/bin/rsh

Report bugs to <bug-tar@gnu.org>.

tar 是 tape archive 的缩写，磁带档案

CentOS 关闭防火墙
CentOS 6:

1） 永久性生效，重启后不会复原

开启： chkconfig iptables on

关闭： chkconfig iptables off

2） 即时生效，重启后复原

开启： service iptables start

关闭： service iptables stop

CentOS 7:

systemctl start firewalld.service#启动firewall
systemctl stop firewalld.service#停止firewall
systemctl disable firewalld.service#禁止firewall开机启动

查询TCP连接情况：

netstat -n | awk ‘/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}’

查询端口占用情况：

netstat -anp | grep portno（例如：netstat –apn | grep 80）