SMBD: No I’m Not Talking About Samba

Let’s say you need high

availability. You can’t afford to have a switch go down or have a network card go bad. You need uptime and you need it now. Now let’s make this even more complicated. Let’s add non native vlans to this ordeal. My weapons of choice are bonding and Gentoo. We need a few things.

1. Linux bonding module – Device Drives > Network device support > <M> Bonding drive support (you can make this a module or build it in but my howto only covers the module)
2. VLAN support – Networking support > Network options > 802.1Q VLAN Support
3. net-misc/vconfig
4. net-misc/ifenslave

After building the modules in your Linux kernel, emerge net-misc/vconfig net-misc/ifenslave . Next you want to setup the bonding module to auto load with your settings. Note that you may have more modules in your autoload file.

# cat /etc/modules.autoload.d/kernel-2.6
…
bonding miimon=100 mode=1

…

Remember to run update-modules. The miimon setting is how often, in milliseconds, the link state of the interface is checked. If it does not have link it will remove the link from the pool. The mode setting indicates the way the interfaces are balanced. There are several modes, but most require that your switch also be configured to use them. In this howto’s case mode 1 is set. Mode 1 is active/backup where you may have one active link up and one or more backups or standbys. If the active fails a backup will take its place.

Next you need to configure the network. The network

configuration file for Gentoo is /etc/conf.d/net . Here is how to setup bonding.

config_eth0=( “null” )
config_eth1=( “null” )

slaves_bond0=”eth0 eth1″

config_bond0=( “192.168.0.1/24” )
routes_bond0=( “default via 192.168.0.254/24” )

Basically you set eth0 and eth1 to have no configuration. This allows the ethernets to be brought up to use, but not configured to do anything or assumed to be dhcp. The slaves_bond0 directive sets which

interfaces are members of the pool of available interfaces. Finally config_ and route_ sets the ip and gateway for your interface.

Now, let’s say you are going to add non native VLANs. The config_ and route_ lines won’t work now. Here is the new config.

config_eth0=( “null” )
config_eth1=( “null” )

slaves_bond0=”eth0 eth1″

config_bond0=( “null” )

vlans_bond0=”100 200″
mtu_bond0=”1496″
vconfig_bond0=( “set_name_type VLAN_PLUS_VID_NO_PAD” )

config_vlan100=( “192.168.0.1/24” )
routes_vlan100=( “default via 192.168.0.254” )
config_vlan200=( “10.0.0.123/24” )

Basically the only difference is the removal of routes_bond0 and setting config_bond0 to null. The vlans_bond0 sets which VLANS to attach the interface to, mtu_bond0 sets the MTU size, and vconfig_bond0 sets VLAN options. Finally it’s time to setup the actual VLAN interfaces, those are config_<vlanid>. In our case we’ve already set them with vlans_bond0, so we have config_vlan100 and config_vlan200. Our default route goes out vlan100, so routes_vlan100 is used and vlan200 is our private interface.

That concludes our bondage training. I hope you all enjoyed and found this informational.

Backups: Slow and Painful

So in my previous post I showed you how to do a a file copy and I mentioned a bit by bit copy. File copies are cool because they copy only the files. Bit by bit copies copies all of the data and includes the zeros. So if you are backing up a 40 gig drive that has 8 gigs of data a file copy will copy the 8 gigs of files where as a bit by bit copy will copy all 40 gigs. Also this means that the output file will be the size of the source drive.

That’s some of the down sides, but here are some good points. A bit by bit copy can copy things like your file system, your master boot record and your partition table. In some cases, you might find it faster to do a bit by bit copy because a file copy must insert files in to the destination file system. On some systems with millions

or more small files a file copy will be much slower. You can also set the destination to another drive and produce an identical copy of the original without having to partition, format, and then copy the data.

That said here is how you can make a quick backup of your system. I will assume your machine uses sda as its root drive. Please keep in mind that your source drive and your destination file must not

be on your source drive.

~ # dd if=/dev/sda of=/mnt/backups/sda.dd

Once this is complete the /mnt/backups/sda.dd file should

be an exact copy of the source drive. It is also possibly to target specific partitions of a drive by setting the if=/dev/sda to if=/dev/sdaX, where X is the partition number of your drive.

Backups: Quick and Dirty

During my career as a systems administrator I’ve learned two basic ways to perform backups. There are basically two different ways to backup a system; file level backups are where you specifically backup the files from the system. The other

way is a bit by bit copy of the storage device. Remember it is important to either be in single user mode or boot to a live CD.

A file copy:

~ # df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda4 145G 100G 39G 73% /
udev 10M 192K 9.9M 2% /dev
shm 1.3G 12K 1.3G 1% /dev/shm
/dev/sda1 38M 25M 12M 68% /boot

These are the file systems I am working with. As per my previous post, it is important to note that traditional copying won’t get everything. We will use the method I mentioned in my previous post to get all the data. We’ll also be backing up to /mnt/backups. For backups, I’m going to use the rsync command. It is pretty powerful and it only copies files that don’t already exist at the destination.

miar mnt # mount -obind / /mnt/root

Once the root file system is mounted on /mnt/root you can back

that up to /mnt/backups. I’ve chosen to put it in a sub folder called root.

miar mnt # rsync -avHSx –numeric-ids –progress /mnt/root/ /mnt/backups/root

Once this complete, and it may take some time, it will be time to go to the next file system. In my above example, /boot is the only other file system that needs to be backed up. The shm and udev are dynamic file systems and are created upon boot. They do not need to be backed up.

miar mnt # rsync -avHSx –numeric-ids –progress /boot/ /mnt/backups/boot

Once this command

finishes your backups are complete or you need to repeat the steps for /usr, /var, /local and or others.