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# Rucksack

From ArchWiki

Rucksack is a simple script and daemon designed for Arch Linux. Rucksack allows the system administrator to set up a unified package cache on individual workstations, exploiting unionfs to combine a remote package cache and a local package cache. By avoiding repeated downloads of core packages rucksack helps to reduce bandwidth consumption and network traffic. The remote cache can reside on any machine within the network, utilizing a variety of shared file systems, including NFS.

Because rucksack mounts the remote cache as read-only there are no security or storage concerns: you can administrate the volume of packages stored from the host machine. However, rucksack also mounts a local cache so that any files that pacman cannot find in the remote cache are downloaded and stored as normal. All this takes place within a seamless single cache. This means that client machine can still keep up to date with an array of packages not used on the remote host machine.

Rucksack is NOT a repository mirroring tool and is focused on avoiding repeated downloads of core packages. It is therefore superior in many ways to the rsync method described in the Local Mirror howto.

## Setup

The rucksack script is not currently available as an Arch Linux package but the source can be found here Rucksack is purely a client side application – it doesn’t need to be installed on the remote cache host. Rucksack relies on unionfs so ensure you install the unionfs module for your kernel. Unionfs is available in the repositories for both the stock and beyond kernels

### Sharing the remote cache

It is important to select the right machine as your remote cache host. We all know that every system should be kept as up to date as possible but the machine storing your cache should be that which is most frequently updated.

The remote cache host doesn’t require any special configuration as such; you merely need to share the pacman cache residing in `/var/cache/pacman/pkg` using your preferred shared filesystem. NFS is the easiest to set up but any shared filesystem that can be mounted from fstab is suitable.

This NFS howto provides all the information you need to set up a secure and reliable NFS share.

(Please add links to further howtos for other shared FSs)

### Setting up the clients

Each client now needs to be configured to access the shared resource created above. You can refer to the howtos above for this step. Once you can successfully mount the shared resource on the client machine you can move to the next step.

#### Creating the caches and mount points

Pacman normally uses one package cache, stored in `/var/cache/pacman/pkg`. The easiest way to set up your caches for rucksack is to move your existing cache to `/var/cache/pacman/local` and create a remote cache mount point and a new pacman cache directory. The pacman cache directory `/var/cache/pacman/pkg` is used as the unionfs mount point.

    # mv /var/cache/pacman/pkg /var/cache/pacman/local
    # mkdir /var/cache/pacman/{pkg,remote}

That’s it!

#### Configure rucksack

Rucksack config options are found in `/etc/conf.d/rucksack`. Currently the only information you need to add is the local cache directory and the mount points for the remote cache and the target pacman cache (almost certainly `/var/cache/pacman/pkg`).

#### Configuring fstab

This is the heart of rucksack. You need to add a line to fstab to mount the shared remote cache on the remote cache mount point created above. This can either be set to mount at boot or can be set noauto and rucksack will mount it as necessary.

#### Starting rucksack

Rucksack should be started at boot by adding rucksack to the DAEMONS array in rc.conf. It can also be started and stopped manually using the following commands:

    # rucksack -start
    # rucksack -stop

Warning: If rucksack is not manually stopped correctly before shutdown then there is a strong chance that one of your mount points will hang and data maybe lost. Therefore I would strongly recommend that you use the daemon to avoid such problems.

### Is that it?

Well, yes! Rucksack is an extremely simple and robust way of utilizing shared file systems and unionfs. You could simply do all of this by hand but I hope rucksack can save you the trouble.

## FAQs

Q. All my clients use KDE but my host doesn’t. How can rucksack help me?

  A. Simple. All you need to do is frequently run `pacman -Syw kde` on the remote cache host to keep the KDE packages cache for use by your client machines.

Q. My pacman cache is stored on a separate local partition, can rucksack deal with that?

  A. Yes. As long as you have configured your machine to correctly mount that partition from within fstab rucksack will try and mount it as necessary. Bear in mind though that the mount point will need to be changed from /var/cache/pacman/pkg.

Retrieved from "https://wiki.archlinux.org/index.php?title=Rucksack&oldid=239532"
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