ext2/3/4 filesystem backup

-u     Update  the  file  /var/lib/dumpdates after a successful dump. The format of /var/lib/dumpdates is
       readable by people, consisting of one free format record  per  line:  filesystem  name,  increment
       level and ctime(3) format dump date followed by a rfc822 timezone specification (see the -u option
       for details). If no timezone offset is specified, times are interpreted  as  local.  Whenever  the
       file  is written, all dates in the file are converted to the local time zone, without changing the
       UTC times. There may be only one entry per filesystem at each level. The  file  /var/lib/dumpdates
       may be edited to change any of the fields, if necessary.

-a     “auto-size”.  Bypass  all  tape length calculations, and write until an end-of-media indication is
       returned.  This works best for most modern tape drives, and is the default. Use of this option  is
       particularly  recommended  when appending to an existing tape, or using a tape drive with hardware
       compression (where you can never be sure about the compression ratio).

-n     Whenever dump requires operator attention, notify all operators in the  group  operator  by  means
       similar to a wall(1).

-f file
       Write  the  backup  to  file;  file  may  be  a  special device file like /dev/st0 (a tape drive),
       /dev/rsd1c (a floppy disk drive), an ordinary file, or -  (the  standard  output).  Multiple  file
       names  may  be given as a single argument separated by commas. Each file will be used for one dump
       volume in the order listed; if the dump requires more volumes than the number of names given,  the
       last  file name will used for all remaining volumes after prompting for media changes. If the name
       of the file is of the form host:file or user@host:file dump writes to the named file on the remote
       host  (which  should  already  exist,  dump  doesn't  create a new remote file) using rmt(8).  The
       default path name of the remote rmt(8)  program  is  /etc/rmt;  this  can  be  overridden  by  the
       environment variable RMT.

Pipelines
    A  pipeline is a sequence of one or more commands separated by one of the control operators | or |&.  The
    format for a pipeline is:

           [time [-p]] [ ! ] command [ [|⎪|&] command2 ... ]

    The standard output of command is connected  via  a  pipe  to  the  standard  input  of  command2.   This
    connection  is performed before any redirections specified by the command (see REDIRECTION below).  If |&
    is used, the standard error of command is connected to command2's standard input through the pipe; it  is
    shorthand  for  2>&1  |.   This  implicit  redirection  of  the  standard  error  is  performed after any
    redirections specified by the command.

    The return status of a pipeline is the exit status of the last command, unless  the  pipefail  option  is
    enabled.   If  pipefail  is  enabled,  the  pipeline's return status is the value of the last (rightmost)
    command to exit with a non-zero status, or zero if all commands exit successfully.  If the reserved  word
    !   precedes  a  pipeline, the exit status of that pipeline is the logical negation of the exit status as
    described above.  The shell waits for all commands in the pipeline to terminate before returning a value.

    If the time reserved word precedes a pipeline, the elapsed as well as user and system  time  consumed  by
    its execution are reported when the pipeline terminates.  The -p option changes the output format to that
    specified by POSIX.  When the shell is in posix mode, it does not recognize time as a  reserved  word  if
    the  next  token begins with a `-'.  The TIMEFORMAT variable may be set to a format string that specifies
    how the timing information should be displayed; see the description of TIMEFORMAT under  Shell  Variables
    below.

    When the shell is in posix mode, time may be followed by a newline.  In this case, the shell displays the
    total user and system time consumed by the shell and its children.  The TIMEFORMAT variable may  be  used
    to specify the format of the time information.

    Each command in a pipeline is executed as a separate process (i.e., in a subshell).

compress or expand files

OpenSSH SSH client (remote login program)

-c cipher_spec
        Selects the cipher specification for encrypting the session.

        Protocol version 1 allows specification of a single cipher.  The supported values are “3des”,
        “blowfish”, and “des”.  3des (triple-des) is an encrypt-decrypt-encrypt triple with three different
        keys.  It is believed to be secure.  blowfish is a fast block cipher; it appears very secure and is
        much faster than 3des.  des is only supported in the ssh client for interoperability with legacy
        protocol 1 implementations that do not support the 3des cipher.  Its use is strongly discouraged
        due to cryptographic weaknesses.  The default is “3des”.

        For protocol version 2, cipher_spec is a comma-separated list of ciphers listed in order of
        preference.  See the Ciphers keyword in ssh_config(5) for more information.

ssh connects and logs into the specified hostname (with optional user name).  The user must prove his/her
identity to the remote machine using one of several methods depending on the protocol version used (see
below).

If command is specified, it is executed on the remote host instead of a login shell.