DICE Disk Partitioning

Here's how the default disk partitioning is decided for DICE machines. Note that this is a snapshot of how things worked in August 2016; things may have changed by the time you read this, and for the canonical information you should refer to the header files in subversion.

Typically the filesystem layout for both desktops and servers is configured through the dice/options/disk-layout.h header this creates a layout for the primary disk (e.g. sda or vda) but leaves all others untouched.

Variables

DICE_DISK_DEFAULT_FS

Controls the default filesystem type used for partitions. On SL6 it is ext3, on SL7 and beyond it is ext4.

FIRST_INSTALL

If this is defined in a machine's LCFG profile, above where the headers are included, then running the DICE install process will repartition the disk without saving anything on it. If it's not defined there then the DICE install process won't partition the disk and will preserve the contents of the local data partition (generally called /disk/scratch).

DICE_LOCAL_PART

When this is defined an additional local partition will be added to the layout which has a free size to use up all remaining space on the disk. Use the variable to specify the mount point, typically this is /disk/scratch.

DICE_DISK_VAR_MPT

The mount point for the "var" partition, usually this is the AFS cache partition which is mounted at /var/cache/afs.

You can use the following variables to control encryption (SL7 only):

DICE_DISK_ENCRYPT_SWAP

If this variable is defined the contents of the swap partition will be encrypted (SL7 only).

DICE_DISK_ENCRYPT_TMP

If this variable is defined the contents of the /tmp partition will be encrypted, note that this means all data in the partition is lost on reboot (SL7 only).

You can use the following variables to adjust the sizes of various partitions:

DICE_ROOTSIZE

Define this variable to alter the size of the root partition, the default is 80Gb.

DICE_SMALL_MAIN_DISK

Define this at the top of the LCFG profile for a machine with a small primary disk. Reduces DICE_ROOTSIZE to be 40Gb.

DICE_SWAPSIZE

By default the size of the swap partition is based on the amount of RAM at install time. Define this variable if a specific size is required.

DICE_DISK_TMP_SIZE

Define this variable to alter the size of the /tmp partition, the default is 10Gb (SL7 only).

DICE_DISK_AFSCACHE_SIZE

Define this variable to alter the size of the AFS cache partition, the default is 8Gb.

DICE_DISK_VAR_SIZE

Define this variable to alter the size of the "var" partition (usually AFS cache and thus DICE_DISK_AFSCACHE_SIZE which is 8Gb).

Desktops

A desktop machine is any machine which includes the dice/options/desktop.h header. In that header DICE_LOCAL_PART is set to /disk/scratch also for SL7 DICE_DISK_ENCRYPT_SWAP and DICE_DISK_ENCRYPT_TMP are enabled.

A standard SL6 DICE desktop will have a partition layout which looks like:

A standard SL7 DICE desktop will have a partition layout which looks like:

Note that the bios_grub partition where grub2 installs the boot loader is essential, it is not mounted though.

Servers

It is recommended that system managers define their own partition layouts to suit the requirements of the services being hosted. This needs to take into consideration issues such as local data storage needs, log files (location and quantity).

A server will include one of the dice/options/server.h or dice/options/small-server.h headers.

Note that neither of the standard server headers adds a scratch disk and on SL7 they do not enable encryption. If the dice/options/small-server.h is used then the root partition size is reduced to 10Gb, the AFS cache size becomes 2Gb and on SL7 the /tmp partition size is 1Gb.

For SL6 the default server partition layout is:

On SL7 the default server partition layout is:

Note that the bios_grub partition where grub2 installs the boot loader is essential, it is not mounted though.

-- StephenQuinney - 02 Aug 2016