mfsbdev.cfg
The file that says which files stored in MooseFS become block devices when the mfsbdev daemon starts. The daemon reads the file when start is given the -i option, and maps one device per line. Writing the file and starting the daemon with it is in Block device operations.
path [ device|* [ linkname|* [ size|* [ bsize|* [ flags ]]]]]
Fields
Empty lines and lines that start with ; or # are ignored. Every other line is one device. The fields stand in the order below, separated by blanks. A field you do not set takes * when a field to its right is set.
| Field | Meaning |
|---|---|
path | The file that becomes the device. The path is relative to the MooseFS root, or to the directory the -S option of start names, not to your local file system. |
device | The network block device to serve it through, as /dev/nbd1. Absent or *: the first free device. |
linkname | The name of the symbolic link created in /dev/mfs for the device. Absent or *: the same default name a mapping made without -n gets. |
size | The size of the device, in bytes or with a unit, as 64MiB. Absent or *: the size of the file. |
bsize | The block size of the device. Absent or *: 4096 bytes. Up to 5.1.0, a line that leaves it out, or writes *, leaves the daemon with no block size, so write it there. |
flags | What the device may do and whether it takes a lock, from the table below. Absent: rw,lock. |
Flags
Several flags stand on one line, separated by commas. Where two flags conflict, such as ro with rw or lock with nolock, the last one counts.
| Flag | Meaning |
|---|---|
ro | A read-only device. |
rw | A read/write device. |
lock | The device takes a lock on the file: shared for ro, exclusive for rw. |
nolock | The device does not require a lock. It tries to take one, and is mapped even when it cannot. |
A word that is none of these is ignored. The daemon prints that word.
Examples
| Line | Meaning |
|---|---|
my_devices/device1 /dev/nbd3 mfsdevice1 67108864 1024 ro | A read-only device of 67108864 bytes, in blocks of 1024 bytes, served through /dev/nbd3 and reachable as /dev/mfs/mfsdevice1. |
my_devices/device2 /dev/nbd7 mfsdevice2 64MiB 1024 ro,nolock | The same, with the size written with a unit, and mapped even when the lock cannot be taken. |