Fix typo (thank Rayis for the report!)

• [DH] README

Fix documentation typo (string -> strong)

• [DH] README

Add -S (--sparse) to the default rsync flags

• [DH] bacap

Avoid creation of dangling symlinks

If rsync fails, possibly the new directory does not exist, so we should
not create the symlink. Because if we create it, the next backup would
not be incremental, because the --link-dest option does not point to an
existing directory.

This patch fixes this by checking the return code of rsync and only
creates the symlink if rsync exits successful or with error 24 ("Partial
transfer due to vanished source files") which is somewhat expected.

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] bacap

Print the backup start time for each host

This can be useful when the backup takes a lot more time that the
expected to finish and we don't know which host(s) caused the long
delay.

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] bacap

Dont use by default rsync --delete option

As we are creating the directory empty (now rsync creates the directory,
cp is not used anymore to create hardlinks) it shouldn't be any weird
files there and we shouldn't need --delete.

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] bacap

Improve tip "Providing a ssh key"

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] README

Remove uneeded rsync flag

rsync --delete-excluded was needed when cp was used to create the
hardlinks. Now that rsync creates them, it is not needed anymore.

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] bacap

Create necessary files for new hosts

When a new host is added to the backup, we need to create the top-level
directory for its backup. Also, don't issue an error when the "current"
symlink can't be removed (because it doesn't exist yet).

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] bacap

Add tip to backup hosts with dynamic IP address

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] README

Fix typos and small documentation errors

• [DH] README

Fix console error reporting when using a LOG_FILE

• [DH] bacap

Add a Tips section to the README

Move some tips that were randomly distributed in the file to the Tips
section and add a couple of new ones.

• [DH] README

Don't provide any default options for ssh

Asuming the user will have a fast and trusted network is not the better
default, it seems more reasonable to trust the user default options.

• [DH] bacap

Let rsync do the hard linking

• [DH] bacap

Add FORCE_SYNC option

FORCE_SYNC forces synchronization even when target directory already
exist. Is useful to synchronize a copy interrupted by an error for
example.

• [DH] bacap

Make pinging hosts configurable

Add a new configuration option to choose whether remote hosts should be
pinged to check if they are up or not. Disabling this option is useful if
your remote hosts don't reply to ICMP pings for security reasons.

• [DH] bacap

Fix doc typos

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] README

Fix extra_flags usage

We need to "clean" extra flags when we start to backup a new host to
make sure we use the correct options for the current host we are backing
up.

Also, we remove some unused variables that were replaced by
extra_flags.

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] bacap

Add example to view the differences between two backups

Signed-off-by: Rodrigo Campos <rodrigo@sdfg.com.ar>

• [DH] README