Luis Bravo's List: Archlinux

• IgnorePkg=linux

  • Skip package from being upgraded.
    O nome dos pacotes pode ser separado por espaço ou então pode-se usar mais de uma linha.
• Installing specific packages

  • # pacman -S package_name1 package_name2 ...
    
    Especificando o repositório (extra na exemplo
    # pacman -S extra/package_name
    
    Também é possível instalar grupos de pacotes. Masi detalhes nesse mesmo site.
    Relação de grupos: em https://www.archlinux.org/groups/
• Removing packages

  • Só o pacote
    # pacman -R package_name
    
    Pacote e dependências não usadas por mais ninguém
    # pacman -Rs package_name
    
    Pacote e dependências não usadas por mais ninguém e pacotes que dependem desse pacote
    # pacman -Rsc package_name
    
    A opção "-n" impede a criação dos arquivos  .pacsave. Por default .pacsave são criados para manter configurações dos usuários.
• Upgrading packages

  • # pacman -Syu
    
    pacman's output is logged in /var/log/pacman.log
    
    Arquivos .pacnew são criados para arquivos de configuração modificados pelo usuário.
    
    Ver também https://wiki.archlinux.org/index.php/Pacnew_and_Pacsave_Files

2 more annotations...

• UEFI does not launch any boot code in the MBR whether it exists or not. Instead it uses a special partition in the partition table called EFI SYSTEM PARTITION
• Each vendor can store its files under <EFI SYSTEM PARTITION>/EFI/<VENDOR NAME>/ folder and can use the firmware or its shell (UEFI shell) to launch the boot program
• An EFI System Partition is usually formatted as FAT32 (mostly) or FAT16.
• Firmware then reads its Boot Manager data to determine which UEFI application to be launched and from where
• Firmware then launches the UEFI application as defined in the boot entry in the firmware's boot manager.
• r the kernel and initramfs (in case of a bootloader like GRUB) depending on how the UEFI application was configured.
• The launched UEFI application may launch another application (in case of UEFI Shell or a boot manager like rEFInd)
• On some UEFI systems the only possible way to launch UEFI application on boot (if it doesn't have custom entry in UEFI boot menu) is to put it in this fixed location: <EFI SYSTEM PARTITION>/EFI/boot/bootx64.efi (for 64-bit x86 system)
• Detecting UEFI Firmware bitness
• Check whether the dir /sys/firmware/efi exists
• UEFI defines variables through which an operating system can interact with the firmware
• efivarfs (efivarfs kernel module, /sys/firmware/efi/efivars) that was designed to overcome the limitations of sysfs-efivars interface
• If efibootmgr completely fails to work in your system, you can reboot into UEFI Shell v2 and use bcfg command to create a boot entry for the bootloader.

  • Como bootar em UEFI Shell v2 ?
• Upstream efibootmgr http://linux.dell.com/git/efibootmgr.git does not support efivarfs. However vathpela's efibootmgr supports efivarfs and is currently used in official efibootmgr pkg
• If you are using Linux EFISTUB booting, then you need to make sure there is adequate space available for keeping the kernel and initramfs files in the ESP.
• GPT partitioned disks

  • Using GPT fdisk (aka gdisk): create a partition with partition type ef00. Then format that partition as FAT32 using mkfs.vfat -F32 /dev/<THAT_PARTITION>

  • Using GNU Parted/GParted: create a FAT32 partition. Set boot flag on for that partition.
• UEFI Shell
• Obtaining UEFI Shell

16 more annotations...

• Some people recommend the use of other options to the Ext4 filesystem such as removing its journal or removing write barriers. Both of those can lead to filesystem corruption and loss of data on systems without UPS.

  • Mas notebooks tem bateria, então deve ser útil não usar journal em filesystems com pouca escrita como um raiz segregado. Usar "/" sem journal, /var separado com journal, /tmp em tmpfs, /home separada com journal, profile e .cache em tmpfs, swap em disco.
• For every partition using Ext4 we add the word discard to the list of options

  • Existe alguma recomendação para usar LVM com SSD ?

• Separate screens

  • Normally the X display has a single identifier such as :0 set in the DISPLAY environment variable, but in this configuration each screen has a different $DISPLAY value. The first screen is :0.0, the second is :0.1 and so on.

  • # Launch a terminal on the second screen
    $ DISPLAY=:0.1 urxvt &
  • 2 more sticky notes...

  • • With this configuration it is not possible to move windows between screens, apart from a few special programs like GIMP and Emacs which have multi-screen support. For most programs you must change the DISPLAY environment variable when launching to have the program appear on another screen

    • Acho que é isso o que eu quero.
      
      This is the original way of configuring multiple monitors with X, and it has been around for decades. Each physical monitor is assigned as an X screen, and while you can move the mouse between them, they are more or less independent.

• hdparm -t /dev/sdx

  • This is only the pure read speed of the hard drive, and is not a valid benchmark, but a value superior to 40MB/s (assuming drive tested while idle) can be considered decent on an average system. hdparm can be found in the Official Repositories.

• Special considerations such as partition alignment, choice of file system, TRIM support, etc. are needed to set up SSDs for optimal performance
• Large cells require different filesystem optimizations than rotating media
• Partitions and filesystems need some SSD-specific tuning. Page size and erase page size are not autodetected.
• Consumer MLC cells at mature 50nm processes can handle 10000 writes each
• Cells wear out
• Daily write volumes have to be balanced against life expectancy.

  • Colocar o /var em disco para os logs não "gastarem" o SSD. O que mais deve ser colocado em disco ? Cache do browser ? O Btrfs ajuda de alguma forma ?
• Native TRIM support is a vital feature that both prolongs SSD lifetime and reduces loss of performance for write operations over time.

  • http://en.wikipedia.org/wiki/TRIM
• Buying the right sized SSD is key. As with all filesystems, target <75 % occupancy for all SSD partitions to ensure efficient use by the kernel
• Tips for Maximizing SSD Performance

  • As of linux kernel version 3.7, the following filesystems support TRIM: ext4, btrfs, JFS, and XFS.
    The Choice of Filesystem section of this article offers more details.
    https://wiki.archlinux.org/index.php/Solid_State_Drives#Choice_of_Filesystem

  • TRIM
    Most SSDs support the ATA_TRIM command for sustained long-term performance and wear-leveling. For more including some before and after benchmark, see this tutorial.
    https://sites.google.com/site/lightrush/random-1/howtoconfigureext4toenabletrimforssdsonubuntu
• Enable TRIM by Mount Flags

  • Enable TRIM for LVM
    Enable issue_discards option in /etc/lvm/lvm.conf

  • Warning: Users need to be certain that kernel version 2.6.33 or above is being used AND that their SSD supports TRIM before attempting to mount a partition with the discard flag. Data loss can occur otherwise!
  • 1 more sticky notes...

  • • Flag discard habilita o TRIM
      
      /dev/sda1  /       ext4   defaults,noatime,discard   0  1
      /dev/sda2  /home   ext4   defaults,noatime,discard   0  2
• I/O Scheduler

  • This article or section is out of date.
    Reason: According to the discussion page, the CFQ scheduler can detect SSDs and modifies its behavior appropriately, so there is no need to change the I/O scheduler.

  • # echo noop > /sys/block/sdX/queue/scheduler
  • 2 more sticky notes...

  • • $ cat /sys/block/sdX/queue/scheduler
      noop deadline [cfq]

    • Consider switching from the default CFQ scheduler (Completely Fair Queuing) to NOOP or Deadline.
• This article or section is out of date.

  Reason: Using tmpfiles.d to set the scheduler does not appear to work on current versions of Arch; The udev method below works perfectly.
• This article or section is out of date.

  Reason: rc.local has been deprecated for some time now; recommend using a custom service.
• Swap Space on SSDs

  • Com bastante memória podemos desabilitar o swap.

  • Or one can simply modify /etc/sysctl.conf as recommended in the Maximizing Performance wiki article:
    
    vm.swappiness=1
    vm.vfs_cache_pressure=50
  • 1 more sticky notes...

  • • # echo 1 > /proc/sys/vm/swappiness
• SSD Memory Cell Clearing

  • The reset is easily accomplished in a three step procedure denoted on the SSD Memory Cell Clearing wiki article.
    
    https://wiki.archlinux.org/index.php/SSD_Memory_Cell_Clearing
• Tips for Minimizing SSD Read/Writes

  • Disabling Journaling on the filesystem

  • Locate High-Use Files to RAM
  • 4 more sticky notes...

  • • noatime Mount Flag

    • Como eu havia imaginado
      
      For systems with both an SSD and an HDD, consider relocating the /var partition to a magnetic disc on the system rather than on the SSD itself to avoid read/write wear.

    • Use iotop -oPa and sort by disk writes to see how much programs are writing to disk

    • Não é tão crítico assim
      
      Note: A 32GB SSD with a mediocre 10x write amplification factor, a standard 10000 write/erase cycle, and 10GB of data written per day, would get an 8 years life expectancy. It gets better with bigger SSDs and modern controllers with less write amplification.

14 more annotations...

• Linux no more needs to reproduce well known solutions as it is capable of proposing new ones on its own, and creating new standards just like it has been successfully doing in other areas.
• As of version 2.10.92-10, fontconfig-infinality-ultimate entirely abandons the “nesting” configuration model known from fontconfig-infinality, and configuration templates found in /etc/fonts/conf.avail.infinality from now on mimic the layout of the generic /etc/fonts/conf.avail as close as possible
• Deploying fontconfig-infinality-ultimate in other Linux distributions should require as little as applying the patches and substituting the generic infinality-settings.sh with a custom one from the bundle
• Using a single fontconfig configuration tree should help avoid potential issues caused by injecting a complex set of additional config files into the primary structure.
• Multiple runtime settings that come with freetype2-infinality, including, among other things, a selection of Windows, Apple and Ubuntu schemes were replaced by a single new one, as needed by fontconfig-infinality-ultimate.
• /etc/profile.d/infinality-settings.sh should not be used in conjunction with any other similar file either supplied with infinality sources, or with other custom packages
• Any previously installed runtime file can be safely removed once freetype2-infinality-ultimate has been installed

5 more annotations...