OS

In this section

• 👢 Boot

  The Boot - starting process

  - BIOS est lancé automatiquement et détecte les périphs.
  - Charge la routine de démarrage depuis le MBR (Master Boot Record) - C'est le disk de boot et se trouve sur le premier secteur du disque dur.
  - Le MBR contient un loader qui charge le "second stage loader"  c'est le "boot loader" qui est propre au système qu'on charge.
  	-> linux a LILO (Linux Loader) ou GRUB ( Grand Unified  Bootloader)
  - LILO charge le noyau en mémoire, le décompresse et lui passe les paramètres.
  - Le noyau monte le FS / (à partir de là, les commandes dans /sbin et /bin sont disponibles)
  - Le Noyau exécute le premier procès "init" 
  

  Conf LILO

  LILO peut avoir plusieurs Noyaux comme choix. Le choix par default : “Linux”. /etc/lilo.conf : Config des parametres du noyau
  /sbin/lilo : pour que les nouveaux params soient enregistrés. -> créé le fichier /boot/map qui contient les blocs physiques où se trouve le prog de démarrage.

• Certificates Authority

  Trust a CA on Linux host

  1# [RHEL] RootCA from DC need to be installed on host: 
  2cp my-domain-issuing.crt /etc/pki/ca-trust/source/anchors/my_domain_issuing.crt
  3cp my-domain-rootca.crt /etc/pki/ca-trust/source/anchors/my_domain_rootca.crt
  4update-ca-trust extract
  5
  6# [Ubuntu] 
  7sudo apt-get install -y ca-certificates
  8sudo cp local-ca.crt /usr/local/share/ca-certificates
  9sudo update-ca-certificates
  

• Cloud-Init

  Troubleshooting

  • cloud-init status --wait usefull for scripting, waiting cloud-init to finish before going to next step.

  • cloud-init status --long

  1status: done
  2extended_status: done
  3boot_status_code: enabled-by-generator
  4last_update: Thu, 01 Jan 1970 00:00:55 +0000
  5detail: DataSourceNoCloud [seed=/dev/sr0]
  6errors: []
  7recoverable_errors: {}
  

  • sudo cloud-init analyze show

   1-- Boot Record 01 --
   2The total time elapsed since completing an event is printed after the "@" character.
   3The time the event takes is printed after the "+" character.
   4
   5Starting stage: init-local
   6|`->no cache found @00.00600s +00.00000s
   7|`->found local data from DataSourceNoCloud @00.01500s +00.12600s
   8Finished stage: (init-local) 00.75400 seconds
   9
  10Starting stage: init-network
  11|`->restored from cache with run check: DataSourceNoCloud [seed=/dev/sr0] @04.21100s +00.00200s
  12|`->setting up datasource @04.22800s +00.00000s
  13|`->reading and applying user-data @04.23400s +00.00500s
  14|`->reading and applying vendor-data @04.23900s +00.00000s
  15|`->reading and applying vendor-data2 @04.23900s +00.00000s
  16|`->activating datasource @04.27100s +00.00100s
  17|`->config-seed_random ran successfully and took 0.000 seconds @04.29500s +00.00100s
  18|`->config-write_files ran successfully and took 0.001 seconds @04.29600s +00.00100s
  19|`->config-growpart ran successfully and took 0.562 seconds @04.29700s +00.56200s
  20|`->config-resizefs ran successfully and took 0.193 seconds @04.86000s +00.19200s
  21|`->config-mounts ran successfully and took 0.001 seconds @05.05200s +00.00100s
  22|`->config-set_hostname ran successfully and took 0.004 seconds @05.05300s +00.00500s
  23|`->config-update_hostname ran successfully and took 0.001 seconds @05.05800s +00.00100s
  24|`->config-update_etc_hosts ran successfully and took 0.005 seconds @05.05900s +00.00500s
  25|`->config-users_groups ran successfully and took 0.216 seconds @05.06400s +00.21600s
  26|`->config-ssh ran successfully and took 0.404 seconds @05.28100s +00.40400s
  27|`->config-set_passwords ran successfully and took 0.001 seconds @05.68500s +00.00200s
  28Finished stage: (init-network) 01.50000 seconds
  29
  30Starting stage: modules-config
  31|`->config-ssh_import_id ran successfully and took 0.001 seconds @07.43300s +00.00100s
  32|`->config-locale ran successfully and took 0.003 seconds @07.43400s +00.00300s
  33|`->config-grub_dpkg ran successfully and took 0.352 seconds @07.43700s +00.35200s
  34|`->config-apt_configure ran successfully and took 0.049 seconds @07.79000s +00.04800s
  35|`->config-timezone ran successfully and took 0.007 seconds @07.83900s +00.00700s
  36|`->config-runcmd ran successfully and took 0.001 seconds @07.84600s +00.00100s
  37|`->config-byobu ran successfully and took 0.000 seconds @07.84700s +00.00100s
  38Finished stage: (modules-config) 00.45400 seconds
  39
  40Starting stage: modules-final
  41|`->config-package_update_upgrade_install ran successfully and took 26.632 seconds @20.56700s +26.63300s
  42|`->config-write_files_deferred ran successfully and took 0.001 seconds @47.20000s +00.00200s
  43|`->config-reset_rmc ran successfully and took 0.000 seconds @47.20200s +00.00100s
  44|`->config-scripts_vendor ran successfully and took 0.001 seconds @47.20300s +00.00000s
  45|`->config-scripts_per_once ran successfully and took 0.000 seconds @47.20300s +00.00100s
  46|`->config-scripts_per_boot ran successfully and took 0.000 seconds @47.20400s +00.00000s
  47|`->config-scripts_per_instance ran successfully and took 0.000 seconds @47.20400s +00.00100s
  48|`->config-scripts_user ran successfully and took 0.558 seconds @47.20500s +00.55800s
  49|`->config-ssh_authkey_fingerprints ran successfully and took 0.005 seconds @47.76400s +00.00500s
  50|`->config-keys_to_console ran successfully and took 0.054 seconds @47.76900s +00.05500s
  51|`->config-install_hotplug ran successfully and took 0.001 seconds @47.82400s +00.00100s
  52|`->config-final_message ran successfully and took 0.001 seconds @47.82500s +00.00100s
  53Finished stage: (modules-final) 27.29600 seconds
  

  • Check the logs: sudo tail -n 50 /var/log/cloud-init-output.log

• Systemd