Difference between revisions of "64-bit FAQ"

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{{i18n|Arch64 FAQ}}

Revision as of 11:45, 23 April 2012

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Below is a list of frequently asked questions about Arch Linux on 64-bit. When all else fails, use the "dual" version of the ISO of choice.

How do I determine if my processor is x86_64 compatible?

Linux users

Run the following command:

$ less /proc/cpuinfo

Look for the flags entry. If you see the lm flag then your processor is x86_64 compatible.

Or you can run this command:

$ grep -q "^flags.*\blm\b" /proc/cpuinfo && echo "x86_64" || echo "not x86_64"

Windows users

Using the freeware CPU-Z you can determine whether your CPU is 64-bit compatible. CPUs with AMD's instructional set "AMD64" or Intel's solution "EM64T" should be compatible with the x86_64 releases and binary packages.

Should I use the 32 or 64 bit version of Arch?

If your processor is x86_64 compatible you should use Arch64.

How can I install Arch64?

Just use our official install ISO CD.

How complete is the port?

The port is ready for daily use in a desktop or server environment.

Will I have all the packages from my 32-bit Arch I am used to?

The Repositories are ported and pretty much everything should work as expected.

Rarely an old package in AUR will only have 'i686' listed, but typically they work for 64-bit too, just try adding 'x86_64'.

Why 64-bit?

It is (under most circumstances) faster and as an added bonus also inherently more secure due to the nature of Address space layout randomization (ASLR) in combination with Position-independent code (PIC) and the NX Bit which is not available in the stock i686 Kernel due to disabled PAE. If your computer is running 4GB or over of usable RAM, 64-bit should be considered as any additional ram cannot be allocated by an 32-bit OS.

Programmers also increasingly tend to care less about 32-bit ("legacy") as "new" x86 CPUs typically support the 64-bit extensions.

There are many more reasons we could list here to tell you to avoid 32-bit, but between the kernel, userspace and individual programs its simply not viable to list every last thing that 64-bit does much better these days.

For further details watch our differences reports. There you will find a list comparing 32-/64-bit package versions.

How can I file bugs?

Simply use Arch's flyspray but select x86_64 in the Architecture field if you think it is a port-related problem!

What repositories should I set up for pacman to use?

All repositories are supported for the port.

How can I patch existing PKGBUILDs for use with Arch64?

Add the following variable to all ported packages:

arch=('i686' 'x86_64') 

Add small patches directly to the sources and md5sums area but use for complete different sources:

[ "$CARCH" = "x86_64" ] && source=(${source[@]} 'other source')
[ "$CARCH" = "x86_64" ] && md5sums=(${md5sums[@]} 'other md5sum')

For any small fix use this in the build area:

[ "$CARCH" = "x86_64" ] && (patch -Np0 -i ../foo_x86_64.patch)

Or when you need more changes:

if [ "$CARCH" = "x86_64" ]; then
    configure/patch/sed      # for x86_64
  else configure/patch/sed   # for i686
fi

What will I miss in Arch64?

Nothing, really. Almost all applications support 64-bit by now or are in the transition to become 64-bit compatible.

The biggest problem are packages that are either closed source or contains x86-specific assembly that is cumbersome to port to 64-bit (typical for emulators).

These applications were previously problematic, but are now available in the AUR and work fine:

  • Acrobat Reader is not available in 64-bit, but you can run the 32-bit version in compatibility mode. There are also many other open source alternatives that can be used to read PDF files.

Everything else should work perfectly fine. If you miss any Arch32 package in our port and you know that it will compile on x86_64 (perhaps you have found it as native packages in another 64-bit distribution), just contact the developers or request a new package in the forums.

Can I run 32-bit apps inside Arch64?

Yes!

  • You can install lib32-* libraries from the multilib repository. To use this repository, you should add the following lines to your /etc/pacman.conf:
[multilib]
Include = /etc/pacman.d/mirrorlist

At this time (December 2011), it contains wine and skype. Furthermore, a multilib compiler is available.

Boot into Arch64, startx, open a term.

$ xhost +local:
$ su
# mount /dev/sda1 /mnt/arch32
# mount --bind /proc /mnt/arch32/proc
# chroot /mnt/arch32
# su your32bitusername
$ /usr/bin/command-you want # or eg: /opt/mozilla/bin/firefox

Some 32-bit apps (like OpenOffice) may require additional bindings. The following lines can be placed in rc.local to ensure you get all you need for the 32-bit apps (assuming /mnt/arch32 is mounted in fstab):

mount --bind /dev /mnt/arch32/dev
mount --bind /dev/pts /mnt/arch32/dev/pts
mount --bind /dev/shm /mnt/arch32/dev/shm
mount --bind /proc /mnt/arch32/proc
mount --bind /proc/bus/usb /mnt/arch32/proc/bus/usb
mount --bind /sys /mnt/arch32/sys
mount --bind /tmp /mnt/arch32/tmp
#comment the following line if you do not use the same home folder
mount --bind /home /mnt/arch32/home

You can then type in a term:

$ xhost +localhost
$ sudo chroot /mnt/arch32 su your32bitusername /opt/openoffice/program/soffice

Can I build 32-bit packages for i686 inside Arch64?

Yes. You can either use

  • the multilib versions of the relevant packages from the multilib repository or
  • a i686 chroot.

Multilib Repository - Multilib_Project

To use the multilib repository, edit your /etc/pacman.conf and uncomment following lines in there:

[multilib]
Include = /etc/pacman.d/mirrorlist

upgrade your system:

# pacman -Syu

and install gcc-multilib and its dependencies

pacman -S gcc-multilib gcc-libs-multilib binutils-multilib libtool-multilib lib32-glibc
Note: If the system has the base-devel package installed, users must replace the [extra] versions with the [mutlilib] versions as shown below.
Note: gcc-multilib is capable of building 32-bit and 64-bit code. You can safely install multilib-devel and remove base-devel on x86_64. See https://bbs.archlinux.org/viewtopic.php?id=102828 for more information.
# pacman -S gcc-multilib gcc-libs-multilib binutils-multilib libtool-multilib lib32-glibc
resolving dependencies...
warning: dependency cycle detected:
warning: lib32-gcc-libs will be installed before its gcc-libs-multilib dependency
looking for inter-conflicts...
:: gcc-libs-multilib and gcc-libs are in conflict. Remove gcc-libs? [y/N] y
:: binutils-multilib and binutils are in conflict. Remove binutils? [y/N] y
:: gcc-multilib and gcc are in conflict. Remove gcc? [y/N] y
:: libtool-multilib and libtool are in conflict. Remove libtool? [y/N] y

Remove (4): gcc-libs-4.6.1-1  binutils-2.21.1-1  gcc-4.6.1-1  libtool-2.4-4

Total Removed Size:   87.65 MB

Targets (7): lib32-glibc-2.14-4  lib32-gcc-libs-4.6.1-1  gcc-libs-multilib-4.6.1-1  binutils-multilib-2.21.1-1
             gcc-multilib-4.6.1-1  lib32-libtool-2.4-2  libtool-multilib-2.4-2

Total Download Size:    25.04 MB
Total Installed Size:   108.27 MB

Proceed with installation? [Y/n]

Compile packages on x86_64 for i686 is as easy as adding the following lines to alternate config file, e.g. ~/.makepkg.i686.conf

CARCH="i686"
CHOST="i686-pc-linux-gnu"
CFLAGS="-m32 -march=i686 -mtune=generic -O2 -pipe -fstack-protector --param=ssp-buffer-size=4 -D_FORTIFY_SOURCE=2"
CXXFLAGS="${CFLAGS}"

and invoking makepkg via the following

$ linux32 makepkg -src --config ~/.makepkg.i686.conf

Chroot

To use a i686 chroot (installation with i686 iso "quickinstall" is recommended for the quick way to install it inside Arch64 or see Arch64 Install bundled 32bit system), install "linux32" wrapper pkg from current to make the chroot behave like a real i686 system. Then use this script to login into the chroot environment as root:

#!/bin/bash
mount --bind /dev /path-to-your-chroot/dev
mount --bind /dev/pts /path-to-your-chroot/dev/pts
mount --bind /dev/shm /path-to-your-chroot/dev/shm
mount -t proc none /path-to-your-chroot/proc
mount -t sysfs none /path-to-your-chroot/sys
linux32 chroot /path-to-your-chroot

If you keep the sources on the x86_64 host system you can add

"mount --bind /path-to-your-stored-sources /path-to-your-chroot/path-to-your-stored-sources" 

to share sources from host to chroot system for pkg building used in /etc/makepkg.conf.

Can I upgrade/switch my system from i686 to x86_64 without reinstalling?

Yes. A forum thread has been created here which outlines steps taken to successfully migrate an install from 32 to 64 bit without losing any configs/settings/data. Note: A large external drive was used for the transfer.

However, you can also start the system with the Arch64 install CD, mount the disk, backup anything you may want to keep that is not a 32-bit binary (e.g: /home & /etc), and install.

You may also want to read Migrating Between Architectures Without Reinstalling.