Miscellaneous Arch Linux Notes

1. AUR PKGBUILD Quick Notes

Arch Linux contains two kinds of packages: precompiled packages that you install through "pacman -S" and configured but not-yet-built packages in the Arch User Repository (AUR). For full instructions on how to build a package in the AUR, see https://wiki.archlinux.org/index.php/Arch_User_Repository

You can search the AUR directly at: https://aur.archlinux.org/ I've found that doing a general search (Google, etc.) on

 
Arch Linux DESIREDPACKAGENAME 

works well, too.

Downloading the tarball from the AUR will be very quick, because it does not contain the package itself. It merely contains the instructions on how to build the package from its original source elsewhere on the net.

Note also that since you're building (compiling) the package from source you must have the Arch Linux development environment installed first:

 
sudo pacman -S base-devel 

Here are my incomplete notes on building from the AUR. (It is a simple process, but do not rely on my notes. Read and actually understanding the process as described on the https://wiki.archlinux.org/index.php/Arch_User_Repository page):

 
# Download the tarball from AUR and put it someplace convenient. 
# Extract tarball (gunzip, tar -xvf ). 
# cd to the extracted directory. 

# The "-s" pulls in dependencies. 
# If there are any, it'll prompt for the password to do 
# an installation of them (you must have sudo installed, of course). 
makepkg -s 

# The makepkg creates a .xz file 

sudo pacman -U /path/to/package.tar.xz 

2. Arch Linux System Updates

Updating your system is something to be taken seriously, and my brief notes to myself here are just that - notes to myself. They're not intended to cover it all.

It is worth taking the time really to understand what a "rolling release" means, how it differs from the more common periodic releases, and the implications that this has for you when you want to update a particular package. In other words, read and understand:

• Arch Linux System Maintenance
• The "Maintaining Arch" section (at least) of Enhancing Arch Linux Stability

Notes:

Before the first run, it is necessary to set up the gpg keys for your system. Read Arch Linux System Maintenance first. GPG key installation will involve at least:

 
sudo pacman-key --init 
sudo pacman-key --populate archlinux 

Before each system update, check Arch Linux News for things which might affect it.

To update:

 
sudo pacman -Syyu 

(The "yy" part forces a refresh of the package database even if it might appear to be up to date; "y" would just refresh it if it appeared not to be up to date.)

Note: Do not sync and then update a particular package. Sync only syncs the databases of packages. It does not update the system. So if you sync and then update an individual package, your updated individual package might be out-of-sync with the actual system you have installed. You must both sync the databases and update the system first. It is best, therefore, always to update the entire system rather than an individual package.

3. How To Get "/media" Back?

There are presently (2014) two packages in Linux for handling automounting of disks: the older "udisks" and the newer "udisks2". The older udisk package mounted removable media (such as USB sticks) in /media, in accordance with the Linux Filesystem Hierarchy standard. The newer udisk2 mounts them in /run/media/$HOME

There are plausible reasons why this might be a good thing (e.g., it lets the / level of the filesystem be readonly). But there are equally plausible reasons why it is not. More importantly, it is a poor design decision from the point of view of practical usability, as it substitutes a long and user-dependent path for a short, simple, fixed one.

One can at present solve this problem by reverting back to udisks, but eventually udisks is going to go away. I suspect that one can also solve it by creating a /media directory linked to /run/media/$HOME, but it isn't a certainty that this will work in all situations. Neither of these solutions is clean.

However, the current udisks2 can be configured to restore the /media behavior. To do this, add the file:

 
/etc/udev/rules.d/99-udisks2.rules 

The file itself should contain the line:

 
ENV{ID_FS_USAGE}=="filesystem|other|crypto",ENV{UDISKS_FILESYSTEM_SHARED}="1" 

or

 
ENV{ID_FS_USAGE}=="filesystem|other",ENV{UDISKS_FILESYSTEM_SHARED}="1" 

(The "crypto" part is not necessary, and not necessarily a good idea.)

In theory, udisks2 will pick up this rule automatically for devices in the future (but not already mounted devices).

See: https://wiki.archlinux.org/index.php/udev#udisks2_-_mount_to_.2Fmedia for a discussion of this.

Note that during some upgrades this configuration file will be destroyed without warning (but no mount point in "/run/media" will be created, either). Once this happens, no USB devices will mount. You must manually re-create it. Here it is as a file: 99-udisks2.rules

4. Where Are ifconfig and netstat

Apparently the "net-tools" package (which contains the ifconfig and netstat programs) hasn't been updated "in years." (It's enough to make one feel old.) The replacements for them are in the iproute2 package (especially the "ip" command).

There's a useful blog entry by Doug Vitale at http://dougvitale.wordpress.com/2011/12/21/deprecated-linux-networking-commands-and-their-replacements/ which discusses equivalent commands using the newer set of tools.

5. Forcing the Wireless Network Down ("Airplane Mode")

The chances that the "airplane mode" button (if present) will work with Linux are slight. (On my Lenovo g500s laptop, pressing it does bring the wireless interface down, but pressing it again does not bring the wireless back up.)

If you have a network configuration file defined in /etc/netctl (for an example, assume you have /etc/netctl/MyNetworkConfig ), then you can bring the network link up and down by:

 
sudo netctl stop MyNetworkConfig 

and

 
sudo netctl start MyNetworkConfig 

This works for both wired and wireless networks.

However, it isn't clear to me that this actually turns off a wireless interface (it simply deconfigures the network's use of it). To turn the network interfaces off entirely, it seems that you need to use the "rfkill" kernel userspace tool. See: http://wireless.kernel.org/en/users/Documentation/rfkill ("RF" for Radio Frequency interface - that is, wireless).

You should consult the documentation, but, briefly, to install:

 
sudo pacman -S rfkill 

To list the current state of the interfaces:

 
rfkill list 

To bring all wireless interfaces down:

 
rfkill block all 

In theory, "rfkill unblock all" should bring everything back up, but for me it does not. Only a reboot works. But at the end of an airplane flight, I'd be shutting my laptop down anyway.

(Actually, this is not true. At the end of an airplane flight I'd be putting my book down.)