Linux Security Cookbook [Electronic resources] نسخه متنی

Recipe 6.3 Copying Files Remotely

6.3.1 Problem

You want to
copy files securely from one computer to another.

6.3.2 Solution

For one file:

$ scp myfile remotehost:
$ scp remotehost:myfile .

For one file, renamed:

$ scp myfile remotehost:myfilecopy
$ scp remotehost:myfile myfilecopy

For multiple files:

$ scp myfile* remotehost:
$ scp remotehost:myfile\* .

To specify another
directory:

$ scp myfile* remotehost:/name/of/directory
$ scp remotehost:/name/of/directory/myfile\* .

To specify an alternate username for
authentication:

$ scp myfile smith@remotehost:
$ scp smith@remotehost:myfile .

To copy a

directory recursively
(-r):

$ scp -r mydir remotehost:
$ scp -r remotehost:mydir .

To preserve file
attributes (-p):

$ scp -p myfile* remotehost:
$ scp -p remotehost:myfile .

6.3.3 Discussion

The
scp command has syntax very similar to that of
rcp or even cp:

scp name-of-source name-of-destination

A single file may be copied
to a remote file or directory. In other words, if
name-of-source is a file,
name-of-destination may be a file
(existing or not) or a directory (which must exist).

Multiple files and directories, however, may be copied only into a
directory. So, if name-of-source is two or
more files, one or more directories, or a combination, then specify
name-of-destination as an existing
directory into which the copy will take place.

Both name-of-source and
name-of-destination may have the following
form, in order:

1. The

   username of the account containing the file or
   directory, followed by
   "@ ". (Optional; permitted only if a
   hostname is specified.) If omitted, the value is the username of the
   user invoking scp.




2. The

   hostname of the host containing the file or directory,
   followed by a
   colon .
   (Optional if the path is present.) If omitted, the local host is
   assumed.




3. The

   path to the file or
   directory .
   Relative pathnames are assumed
   relative to the default directory, which is the current directory
   (for local paths) or the remote user's home
   directory (for remote paths). If omitted entirely, the path is
   assumed to be the default directory.

Although each of the fields is optional, you cannot omit them all at
the same time, yielding the empty string. Either the hostname (item 2) or the directory path (item 3) must be present.

Whew! Once you get the hang of it, scp is pretty
easy to use, and most scp commands you invoke will
probably be pretty basic. If you prefer a more interactive interface,
try
sftp
, which resembles
ftp.

If you want to "mirror"
a set of files securely between machines, you could use scp
-pr, but it has disadvantages:

• scp follows symbolic links automatically, which you
  might not want.




• scp copies every file in its entirety, even if
  they already exist on the mirror machine, which is inefficient.

A better alternative is
rsync
with
ssh, which optimizes the transfer in various ways
and needn't follow symbolic links:

$ rsync -a -e ssh mydir remotehost:otherdir

Add -v and progress for
more verbose output:

$ rsync -a -e ssh -v --progress mydir remotehost:otherdir

6.3.4 See Also

scp(1), sftp(1), rcp(1), rsync(1).