FreeBSD Notes Revision as of Monday, 21 December 2015 at 02:30 UTC

Miscellaneous

System Information

You’ll find everything you need in /var/run/dmesg.boot or in the
output of sysctl -a. Some examples:

 # Memory
 grep memory /var/run/dmesg.boot
 
 # No. of CPUs
 grep CPU /var/run/dmesg.boot

Kernel Modules

'''kldstat''' shows all loaded modules. '''kldload''' loads a
module, '''kldunload''' unloads a module.

Firewall

I used the venerable IPFW. In /etc/rc.conf enable the firewall and
provide a script:

 firewall_enable="YES"
 firewall_script="/opt/firewall"

Then reboot. I used my own simple script at
git://git.example.com/it.firewall.ipfw. However, given that this is
exactly what OS X 10.6 (and below) use for a firewall, you’ll find
either WaterRoof or NoobProof
pretty awesome for some complicated rules. You’ll have to modify their
outputs to script format.

Listing Disks

Can do one of the following

 # For SCSI
disks
 cat /var/run/dmesg.boot | grep da 
 
 # or
 gpart show

SNMP

You’ll need to install
bsnmp to get this working.

Mounting XFS

 kldload xfs
 mount -t xfs -o ro /dev/da15p1 /mnt

If you get an “Operation not permitted” error, check your filesystem.
For XFS, these packages might be helpful

 pkg_add -r xfs xfsprogs xfsinfo

The backspace ‘problem’ in vim

 echo 'set backspace+=start,eol,indent' >> ~/.vimrc

A note on /etc/rc.conf

If you screw up this file, you’re screwed in turn. A single missing
quote and you’ll boot into a read-only system. Be careful, and use
sysinstall if you can.

The Ports Tree

See the “Obtaining the Ports
Collection”
section of the manual if you forgot to install the tree. To update, just
run portsnap update.

Installing bash

As root,

 portsnap update extract
 cd /usr/ports/shells/bash
 make install clean
 
 # Now change your shell
 chsh -s /usr/local/bin/bash nikhil

Installing mkfile

Quicker alternative to ye olde dd:

 cd /usr/ports/sysutils/mkfile; make install clean

Installing Binaries

Use the packages
system.

 pkg_add -r vim

Searching ports

 cd /usr/ports
 make search name=package

NFS Exports

Here’s the pertinent
page from the
FreeBSD manual that describes how to set these up.

ZFS

You will need to increase kmem to prevent panics. Check vm.kmem_size
and vm.kmem_size_max using:

 sysctl -a

If the values look appropriate, skip the “Loader
Tunables”
section of the manual.

Now start ZFS with:

 echo 'zfs_enable="YES"' >> /etc/rc.conf
 /etc/rc.d/zfs start

Creating a zpool

I had twelve 3TB disks I wanted in a RAID6. Sun calls it “RAIDZ2”, since
it averts the RAID write
hole. I wanted to call
my pool “data”:

 zpool create data raidz2 da1 da2 da3 da4 da5 da6 da7 da8 da9 da10 da11 da12

I also had a 256GB solid-state cache drive to speed up performance using
ARC. Its
device name is da16

 zpool add data cache da16

Finally, the ZFS tuning guide
is a must-read. There’s also a longer, evil
version.

Using an existing pool

I had to reinstall FreeBSD after some XFS weirdness. I was able to get
my old pool back with

 zpool import

This scans all drives and lists any available pools. Then actually
import the pool with

 zpool import data

Migrating ZFS pools

 # On the old server, export the pool ("zpool export -f data" to force)
 zpool export data
 
 # You've now moved the disks to a new server and are on it right now
 
 # Scan for zpools
 zpool import
 
 # Import the zpool (use "-f" if necessary)
 zpool import -f data

It’s magical: zpool will also tell you the host that the drives were on,
which ones are missing, etc.

Creating Filesystems

It’s possible to mount and use zpools. But you will miss out on awesome
things that ZFS is known for. So create a filesystem:

 zfs create data/users

 # Set compression on
 zfs set compression=gzip data/users

You may want to think twice before you set compression and
deduplication. They take a heavy toll on memory and performance. Here
are some resources:

Snapshots and Clones

Using date +%Y-%m-%dT%k:%M:%S for a nice ISO-8601 formatted date:

 # Take a snapshot
 zfs snapshot tank/data@2012-09-09T18:06:49

 # DIsplay snapshots
 zfs list -t snapshot

NFS

ZFS is awesome with NFS. Here, I share a filesystem with my trusted
network, after setting up my NFS server according to the FreeBSD
manual.

 zfs sharenfs='-network 10.212.8.0 -mask 255.255.255.0 -maproot root' tank/home

Export data is not written to /etc/exports (as you would expect) but
to /etc/zfs/exports. Check your mounts with the usual:

 [root@lucifer ~]# showmount -e
 Exports list on localhost:
 /tank/home                         10.212.8.0

Unlike traditional NFS, you don’t have to restart mountd every time
you redefine your mount points.

Here are further resources:

Other Resources