Zápisky linux admina: Grub

root@guliverkel:/home/martin# mkdir /media/data2/grub
root@guliverkel:/home/martin# cp /boot/grub/grub.cfg /media/data2/grub

root@guliverkel:/home/martin# ls -lh /media/data2/grub
total 12K
-r--r--r-- 1 root root 12K Dec 17 08:08 grub.cfg

3. Pozriem sa na to, akú konkrétnu verziu Debianu mám, plus aké mám jadro:

root@guliverkel:/home/martin# cat /etc/*release
PRETTY_NAME="Debian GNU/Linux 9 (stretch)"
NAME="Debian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
root@guliverkel:/home/martin# uname -r
4.9.0-8-amd64

4. Môžem spustiť prvý krok updatu (apt-get update) alebo v týchto novších verziách stačí apt update

root@guliverkel:/home/martin# apt update
Ign:1 http://ftp.sk.debian.org/debian stretch InRelease
Get:2 http://ftp.sk.debian.org/debian stretch Release [118 kB]
Get:3 http://ftp.sk.debian.org/debian stretch Release.gpg [2,365 B]
Get:4 http://security.debian.org/debian-security stretch/updates InRelease [94.3 kB]
Get:5 http://ftp.sk.debian.org/debian stretch/main Sources [6,747 kB]
Get:6 http://security.debian.org/debian-security stretch/updates/non-free Sources [1,216 B]
Get:7 http://security.debian.org/debian-security stretch/updates/main Sources [202 kB]
Get:8 http://security.debian.org/debian-security stretch/updates/main amd64 Packages [509 kB]
Get:9 http://security.debian.org/debian-security stretch/updates/main Translation-en [224 kB]
Get:10 http://security.debian.org/debian-security stretch/updates/non-free amd64 Packages [1,596 B]
Get:11 http://ftp.sk.debian.org/debian stretch/contrib Sources [44.7 kB]
Get:12 http://ftp.sk.debian.org/debian stretch/non-free Sources [79.4 kB]
Get:13 http://ftp.sk.debian.org/debian stretch/main amd64 Packages [7,086 kB]
Get:14 http://ftp.sk.debian.org/debian stretch/main Translation-en [5,385 kB]
Get:15 http://ftp.sk.debian.org/debian stretch/non-free amd64 Packages [78.3 kB]
Get:16 http://ftp.sk.debian.org/debian stretch/non-free Translation-en [80.3 kB]
Get:17 http://ftp.sk.debian.org/debian stretch/contrib amd64 Packages [50.9 kB]
Fetched 20.7 MB in 6s (3,284 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
83 packages can be upgraded. Run 'apt list --upgradable' to see them.

5. Tu mi vyhodí, čo bude upgradovať (len časť vypíšem)

root@guliverkel:/home/martin# apt list --upgradable
Listing... Done
base-files/oldstable 9.9+deb9u11 amd64 [upgradable from: 9.9+deb9u9]
debian-archive-keyring/oldstable 2017.5+deb9u1 all [upgradable from: 2017.5]
e2fslibs/oldstable 1.43.4-2+deb9u1 amd64 [upgradable from: 1.43.4-2]
e2fsprogs/oldstable 1.43.4-2+deb9u1 amd64 [upgradable from: 1.43.4-2]

6. spustím upgrade balíčkov:

root@guliverkel:/home/martin# apt upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following NEW packages will be installed:

83 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 176 MB of archives.
After this operation, 244 MB of additional disk space will be used.

7. spustím apt dist-upgrade

root@guliverkel:/home/martin# apt dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@guliverkel:/home/martin#

8. Keďže sa natiahli aj nejaké nové manuály, updatujem aj tie pomocou príkazu catman

catman - update man stránok

(niečo z catmanu)

root@guliverkel:/home/martin# catman

Updating cat files for section 1 of man hierarchy /usr/share/man
2to3-2.7, 2to3-3.5, 7z, 7za, 7zr, Xorg.wrap, acpi_available, add-apt-repository, apm_available, appres, appstreamcli, apropos, apt-extracttemplates, apt-ftparchive, apt-listchanges, apt-sortpkgs, ar, arch, ark, asn1parse, aspell,

9. rebootujem operačný systém (reboot and pray)

init 6

10. zistím, či sa nezmenil grub, verziu OS a jadra:

root@guliverkel:/home/martin# cat /etc/*release
PRETTY_NAME="Debian GNU/Linux 9 (stretch)"
NAME="Debian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
VERSION_CODENAME=stretch
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
root@guliverkel:/home/martin# uname -r
4.9.0-8-amd64
root@guliverkel:/home/martin# uptime -s
2019-12-17 08:22:25

pondelok 16. decembra 2019

Keď potrebujeme do single-user-modu

Občas sa potrebujeme dostať do single user modu alebo do runlevel 1. (Napríklad server je dole (je vypnutý, alebo zahltený)

Keď je server zahltený, potrebujeme sa dosať do user-single-modu a v ňom povoliť, aby niektoré služby nenabehli.

Napríklad, na sieťovej karte eth2 beží zákaznická aplikácia, ale idú vymeniť sieťovku. (eth2 je sieť pre zákazníka.)

My sa musíme dostať do single-user-modu a vypnúť aplikáciu pri štarte. Technik vymení sieťovú kartu, reštartuje sa server, my zistíme konekciu a až potom sa zapne aplikácia ručne. Ako to urobiť?

1. zapneme server

2. prídeme do GRUBu

3. stlačíme písmeno e ako edit

4. zadáme číslo 1 na konci, aby nabehol do runlevel 1 (ako vidíme tu: https://www.debuntu.org/wp-content/uploads/2012/12/grub2-runlevel1.png )

5. prídeme do sinlgemodu a vypneme službu pri štarte:

A) pre SysV chkconfig služba_app off

viac o tom tu: https://www.thegeekdiary.com/how-to-enable-or-disable-service-on-boot-with-chkconfig/

B) pre systemD: systemctl disable applikacia

6. vypneme stroj, kontaktujeme technika a čakáme na neho, kým vymení sieťovú kartu

7. zapneme stroj a skontrolujeme, či sieťovku nahodilo a či cez ňu tečie konekcia

8. ak áno, zapneme službu a pridáme do systému, aby nabehla po boote:

A) pre SysV chkconfig služba on

B) pre systemD systemctl enable applikácia