Mounting Storage on CoreOS

CoreOS is a powerful Linux distribution built to make large, scalable deployments on varied infrastructure simple to manage. Based on a build of Chrome OS, CoreOS maintains a lightweight host system and uses Docker containers for all applications.

Mounting Portable Storage

All secondary mount files go in the /etc/systemd/system directory as the system level mounts are in a directory that is read-only in CoreOS. You will create a MOUNTPOINT.mount file. The Where section of the .mount file must match the filename. If the mount point is not directly off of / you have to name the file using the following syntax: path-to-mount.mount. As you can see in the following example we are wanting to mount the portable storage drive to /mnt/www so we name the file mnt-www.mount.

You have to use fdisk or parted to create the partition and make sure that the filesystem you create matches the one listed in the .mount file or else the service will fail to start.

[Unit]
Description = Mount for Portable Storage

[Mount]
What=/dev/xvdc1
Where=/mnt/www
Type=ext4

[Install]
WantedBy = multi-user.target

CoreOS uses systemd so in order to make the mount point survive a reboot you must enable the *.mount file. If you use the '--now' flag the partition will be mounted immediately and set to start on boot.

$ systemctl enable --now mnt-www.mount

Mounting NFS/File Storage

The process for mounting our Endurance/Performance File Storage is pretty much the same, but since the mount is NFS we can specify some additional options using the Options= line in the mount file. In the following example we are setting the NFS to mount at /data/www.

$ cat data-www.mount
[Unit]
Description = Mount for Container Storage
[Mount]
What=nfsdal0501a.service.softlayer.com:/SL01SVxxxxxxxx_2
Where=/data/www
Type=nfs
Options=vers=4,sec=sys,noauto
[Install]
WantedBy = multi-user.target

We can now enable the mount and check that it is mounted properly.

systemctl enable --now /etc/systemd/system/data-www.mount
cluster1 ~ # mount |grep data
nfsdal0501a.service.softlayer.com:/SL01SXXXXXX_2 on /data/www type nfs4 (rw,relatime,vers=4.0,rsize=65536,wsize=65536,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=10.81.x.x,local_lock=none,addr=10.1.x.x)
 

Mounting NAS/Cifs

Mounting a cifs share is not natively supported in CoreOS but there is a pretty easy workaround to allow the host system to mount NAS shares. You will use a container to build the mount.cfis module and then copy it to the CoreOS system
 
On the CoreOS system run the following to download and drop in to a Fedora container:  
docker run -t -i -v /tmp:/host_tmp fedora /bin/bash
 
Once you are in the container you will want to run the following to build the cifs utility
dnf groupinstall -y "Development Tools" "Development Libraries"
dnf install -y tar
dnf install -y bzip2
curl https://ftp.samba.org/pub/linux-cifs/cifs-utils/cifs-utils-6.4.tar.bz2 | bunzip2 -c - | tar -xvf -
cd cifs-utils-6.4/
./configure && make
cp mount.cifs /host_tmp/
 
Now that the mount.cifs file has been copied to the host machine you can exit the docker container by issuing the 'exit' command or pressing 'ctrl+d'. When you are back in the CoreOS system you can mount the CIFS share with the following command:
/tmp/mount.cifs //nasXXX.service.softlayer.com/USERNAME -o username=USERNAME,password=PASSWORD /path/to/mount
 

Mounting ISCSI

This is currently not supported in CoreOS but is in line for a future release - https://github.com/coreos/bugs/issues/634