mjhjmtu

I have one server with net connectivity, where I can use "yum install $PACKAGE".

I want some yum command, like yum cache-rpms $PACKAGE $DIRECTORY such that all required RPM files will be downloaded to $DIRECTORY, which will also have a file (Install.sh) stating the order in which to install these RPMs, on many other servers without net connectivity.
Install.sh may even be a shell script, which has the same behaviour as yum install $PACKAGE, except that it will not use the network, but will only use $DIRECTORY.

Possible?

I am looking for a general solution where yum and RPM is available, but for specificity: It is on a set of CENTOS 6.7 servers.

Here's a specific example using "httpd" as the package to download and install. This process was tested on both CentOS6 and CentOS7.

Install the stuff you need and make a place to put the downloaded RPMs:

# yum install yum-plugin-downloadonly yum-utils createrepo
# mkdir /var/tmp/httpd
# mkdir /var/tmp/httpd-installroot

Download the RPMs. This uses the installroot trick suggested here to force a full download of all dependencies since nothing is installed in that empty root. Yum will create some metadata in there, but we're going to throw it all away. Note that for CentOS7 releasever would be "7".

# yum install --downloadonly --installroot=/var/tmp/httpd-installroot --releasever=6 --downloaddir=/var/tmp/httpd httpd

Yes, that was the small version. You should have seen the size of the full-repo downloads!

Generate the metadata needed to turn our new pile of RPMs into a YUM repo and clean up the stuff we no longer need:

# createrepo --database /var/tmp/httpd
# rm -rf /var/tmp/httpd-installroot

Configure the download directory as a repo. Note that for CentOS7 the gpgkey would be named "7" instead of "6":

# vi /etc/yum.repos.d/offline-httpd.repo
[offline-httpd]
name=CentOS-$releasever - httpd
baseurl=file:///var/tmp/httpd
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6

To check the missing dependencies:

# repoclosure --repoid=offline-httpd

I haven't figured out why on CentOS7 this reports things like libssl.so.10(libssl.so.10)(64bit) missing from httpd-tools when openssl-libs-1.0.1e-51.el7_2.2.x86_64.rpm (the provider of that library) is clearly present in the directory. Still, if you see something obviously missing, this might be a good chance to go back and add it using the same yum install --downloadonly method above.

When offline or after copying the /var/tmp/httpd repo directory to the other server set up the repo there:

# vi /etc/yum.repos.d/offline-httpd.repo
[offline-httpd]
name=CentOS-$releasever - httpd
baseurl=file:///var/tmp/httpd
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
# yum --disablerepo=* --enablerepo=offline-httpd install httpd

Hopefully no missing dependencies!

Seems you're asking for yumdownloader which is contained in the package yum-utils. There are already a few questions and answers about this, see e.g. Download all dependencies with yumdownloader, even if already installed? or How do I find package URLs with Yum?

yumdownloader will download the packages, although it will not generate a file Install.sh as the order can be determined by yum itself, so you can install the packages on the target box via
yum install ./*rpm in the folder with your downloaded packages (which needs to include all dependencies compared to a base installation - see the first link above regarding repotrack)

I needed it several times, so I automated @Steve Bonds answer. Just be sure do define PKG as the package to install on both machines (Disclaimer: for CentOS 7. For CentOS 6, change the --releasever and CentOS-7 spot.

online machine

PKG=... # NAME OF THE PACKAGE TO INSTALL ON OFFLINE MACHINE
yum install --downloadonly --installroot=/tmp/$PKG-installroot --releasever=7 --downloaddir=/tmp/$PKG $PKG
createrepo --database /tmp/$PKG
rm -rf /tmp/$PKG-installroot
rsync -arv /tmp/$PKG/ [IP of the machine]:/tmp/$PKG

on offline machine:

PKG=... # NAME OF THE PACKAGE
echo "[offline-$PKG]
name=CentOS-$releasever - $PKG
baseurl=file:///tmp/$PKG/
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7" > /etc/yum.repos.d/offline-$PKG.repo

# install package offline:
yum --disablerepo=* --enablerepo=offline-$PKG install --nogpgcheck $PKG