Compressing folder without using additional space on the drive

Solution 1:

You can give a command to compress to stdout over ssh and redirect stdout localy to a file. Something like:

ssh user@host "tar c /mydir | gzip -f" > myarchive.tar.gz

Solution 2:

The following tools are available in Ubuntu, and I have checked that rsync, gzip and tar are also available in MacOS.

rsync which can copy files and/or directory trees locally and via a network
gzip which compresses single files
tar which can create an archive with many files and directory trees, and compress, if you specify it

Change directory

Change directory with

cd path-to-source-directory

to the directory that you want to compress.

`rsync`

I don’t have physical access to the server. I always communicate via ssh. I’ll look up rsync. Thanks.

rsync is a powerful copy tool, and it has a built-in check, that the transfer is correct.

It can copy files and/or directory trees locally and via a network
It is often used for backup
- locally to an external drive or
- via a network connection to a server or between servers

It is straightforward to use rsync, if you have Ubuntu at both ends of the connection, and I checked that there is an rsync version also in MacOS.

I like the following command line where the option

-H takes hard links into account (and avoids double transfers/copies); if there are no hard links, you should remove this option.
-a 'archive' makes a copy that suits backup or synchronizing
-v 'verbose' creates output of all files to be copied with -n and all files copied in the real case (without -n)
-n makes it a 'dry run', just showing what it 'wants to do'
```
rsync -Havn source/ target
```

In your case the source is in the server, and you run via the ssh connection. So, in the client (your Mac computer), run

rsync -avn user-id@ip-address:/path-to-source-directory/ path-to-target-directory

Please notice the trailing slash after the source directory.

If it looks good, you can let it do the transfer with the following command (remove the n for 'dry run')

rsync -av user-id@ip-address:/path-to-source-directory/ path-to-target-directory

Tips and comments

After the transfer, you can do what you want with the copy in the target directory. I think you want to compress it, and I suggest that you use tar for that purpose and create a tarball.
If you cannot run rsync or gzip or tar in your MacOS, you can boot your Mac computer from a USB pendrive or DVD disk with Ubuntu, and run the programs that way. (The advice to boot the computer from a USB pendrive or DVD disk with Ubuntu applies also to a computer with Windows.)
You can read the built-in manual man rsync, man gzip and man tar in your Ubuntu 16.04 LTS, and I am sure that you can find good tutorials via the internet.

`gzip`

Change directory with cd path-to-source-directory to the directory that you want to compress.

Compress single files with

gzip -c file > path-to-external-directory/file.gz

Change directory to where you want to extract the file and run gunzip to uncompress

cd to-where-you-want-to-extract-the-files
gunzip -c path-to-external-directory/file.gz > file

`tar`

Change directory with cd path-to-source-directory to the directory that you want to compress.

Compress a group of files to a 'tarball', for example

tar -cvzf path-to-external-directory/file.tar.gz file1 file2 file3

or if there is space enough in the target partition on the external drive for the whole directory

tar -cvzf path-to-external-directory/file.tar.gz .

The space and final dot are important.

You can 'look into' the tar file with the command

tar -tvf path-to-external-directory/file.tar.gz

Extract the compressed files from the tarball with the following commands

cd to-where-you-want-to-extract-the-files
tar -xvf path-to-external-directory/file.tar.gz