NTECS Consulting

Using HAMMER as root filesystem on DragonFly

This article briefly describes how to install DragonFly BSD on a HAMMER filesystem, i.e. using HAMMER as the root filesystem. Note that I make the assumption that the DragonFly installation will use the entire disk, which in my case is disk ad4. Make sure that the DragonFly version you are using includes my RootOnHammer patches which should be the case for any release after 2.0 and every snapshot ISO image from now on. By the way, the whole approach is similar to ZFSOnRoot except that I will not use the installer.

Let’s go

Start the live-cd installer and enter the root prompt.

Partition ad4 creating one slice covering the entire disk.

fdisk -B -I ad4

Generate a disklabel in your favourite editor that looks like the following one and save it under /tmp/disklabel.ad4s1.

#          size     offset    fstype
  a:     262144          0    4.2BSD        #     128.000MB
  b:    6291456     262144      swap        #    3072.000MB
  c:  234441585          0    unused        #  114473.430MB
  d:  227887984    6553600    4.2BSD        #  111273.430MB

I’m using 128 MB for the boot partition (a), which should be enough to hold several kernels and it’s modules. Note that I am using 3 GB for the swap partition (b). The remaining space is left for the HAMMER partition (d).

Then store the disklabel onto your disk:

disklabel -R -r ad4s1 /tmp/disklabel.ad4s1

Create the boot filesystem (UFS) and the HAMMER filesystem:

newfs /dev/ad4s1a
newfs_hammer -L Root /dev/ad4s1d

At first we set up the boot filesystem by mounting it and copying the /boot directory, the kernel and it’s modules onto it:

mount /dev/ad4s1a /mnt
cpdup -vvv /boot /mnt/boot
cpdup -vvv /kernel /mnt/kernel
cpdup -vvv /modules /mnt/modules

Then we adjust /mnt/boot/loader.conf to use our HAMMER partition ad4s1d as root filesystem:

touch /mnt/boot/loader.conf
echo 'vfs.root.mountfrom="hammer:ad4s1d"' >> /mnt/boot/loader.conf

That’s all we have to do for the boot partition, so let’s unmount it:

umount /mnt

Next we continue with the HAMMER partition:

mount_hammer /dev/ad4s1d /mnt

Onto this partition we will install all remaining parts of DragonFly. It’s as easy as copying the files from the live-cd to the HAMMER partition:

cpdup -vvv /bin /mnt/bin
cpdup -vvv /sbin /mnt/sbin
cpdup -vvv /root /mnt/root
cpdup -vvv /usr /mnt/usr
cpdup -vvv /var /mnt/var
cpdup -vvv /dev /mnt/dev
cpdup -vvv /etc.hdd /mnt/etc

cp /.cshrc /.profile /mnt
mkdir /mnt/mnt /mnt/proc /mnt/tmp

We further want to mount the boot partition into /bootdir, and use /boot as short-cut (symlink) to /bootdir/boot:

mkdir /mnt/bootdir
cd mnt
ln -s bootdir/boot boot
cd ..

Note that the root partition is currently mounted as /mnt so the mkdir /mnt/bootdir above is actually creating the directory /bootdir on the root partition.

We also want to edit /mnt/etc/fstab to contain the following:

# Device            Mountpoint      FStype  Options         Dump    Pass#
/dev/ad4s1a         /bootdir        ufs     rw              1       1
/dev/ad4s1b         none            swap    sw              0       0
/dev/ad4s1d         /               hammer  rw              1       1
/dev/cd0            /cdrom          cd9660  ro,noauto       0       0
proc                /proc           procfs  rw              0       0

You might want to edit /mnt/etc/rc.conf now or later after we have booted into the system.

That’s all, so we unmount the HAMMER root partition and reboot (don’t forget to remove the live-cd):

umount /mnt
reboot

Once we are up and running in our new HAMMER-powered DragonFly system, we want to set up the timezone edit /etc/rc.conf and set the root password. You can easily set your timezone via:

tzsetup

You also might want to make /usr/obj non-history aware:

chflags nohistory /usr/obj
chflags noshistory /usr/obj   # do we need this?

Checkout the pkgsrc sources:

cd /usr
make pkgsrc-checkout

What I also found to be very useful is to extend /usr/pkg/etc/mk.conf for the following two lines:

WRKOBJDIR=/usr/obj
CREATE_WRKDIR_SYMLINK=no

This tells pkgsrc to not create a work directory within each pkgsrc package where it extracts the sources and compiles the application. Instead it will use /usr/obj.

As we don’t want to backup and mirror all the contents of /usr/obj as that data should be considered temporary data of no value, we can create it’s own HAMMER pseudo-filesystem for it. This allows us to treat it separately for pruning and mirroring operations.

rmdir /usr/obj
cd /usr
hammer pfs-master obj

As HAMMER’s pseudo-filesystems are represented by symlinks it isn’t possible to assign access rights to them or flags like nohistory, but there should be a workaround using null mounts:

# We rename the PFS to obj.pfs
mv /usr/obj /usr/obj.pfs

# We create a directory /usr/obj, which holds the permissions 
mkdir /usr/obj

# Finally we null mount /usr/obj.pfs on top of /usr/obj
mount_null /usr/obj.pfs /usr/obj

We’d probably like to do the same for /tmp:

rm -rf /tmp
mkdir /tmp
chmod 1777 /tmp # sticky flags for /tmp

cd /
hammer pfs-master tmp.pfs
mount_null /tmp.pfs /tmp

Enjoy DragonFly and HAMMER!