Arista Linux Essentials (1)

From the course - "Arista Linux Essentials"

Linux Flavors

• Linux Distribution = Distro
• Generally includes:
• Kernel
• Package manager
• GNU tools and libraries
• Documentation
• GUI
• Debian
• All Ubuntu are Debian distro
• Gentoo
• For power users
• ChromeOS is based on Gentoo
• Android:
• Uses a Linux Kernel
• NO GNU tools and libraries, like glibc
• SUSE
• Fedora:
• Red Hat, CentOS
• Oracle's Unix OS
• Not Linux anymore because changing kernel 
• Arista EOS is Fedora Core
• No change in kernel
• ver 18 or 21 now

Bootup

• Boot Loaders:
• Same on all computers
• Multi-stage
• First: BIOS/POST
• Stored in ROM or NVRAM
• Initialize system hw
• MBR (Master Boot Record, Boot Loader) 
• Not OS-specific
• Examples: Coreboot, LILO, GRUB
• @arista switch, Aboot = a mini linux
• Point to VBR
• VBR (Volume Boot Record) .... OS Boot .... Kernel
• OS Boot
• dmesg display kernel message buffer

Arista Boot:

• Power On:
• BIOS
• Active partition
• Aboot -> init
• init -> boot-config
• ctrl - C to stop Aboot calls kexec
• EOS Kernel:
• Aboot calls kexec

EOS Boot Stages

• EOS Stage 1:
• /mnt/flash/persist
• boot hooks - patch, bug fix here
• not change kernel, change boot
• Hw Init:
• FRU initialize
• Cell type config - module/fixed, supervisor
• hw device tree
• EOS Stage 2:
• Kernel modules
• ProcMgr
• SysDB
• Launcher

Init/runLevel:

• scripts in /etc/init.d
• init <runlevel>

Package Management:

• wget - a web client to download files
• in aboot
• curl - more protocol support, http/ftp/imap/scp/....
• not in aboot
• Package Managers:
• different distros use different manager
• Debian/Ubuntu
• uses dpkg
• format is .deb
• advanced tool apt, manage dependencies
• apt-get, manage installation
• Fedors (EOS) 
• uses rpm
• format is .rpm
• yum manage dependencies
• as Fedora 18, yum is replaced by dnf
• sudo dnf install sysstat