k8s - Cheet Sheet

This is a work in progress

Storage:

Storage class:

Make a storage class non-default:

kubectl patch storageclass <your-class-name> -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"false"}}}'

Linux: Add timestamp in history

• Add the timestamp in history command (in ~/.bashrc):

export HISTTIMEFORMAT="%F %T : "

  437  2017-02-06 17:04:28 : history
  438  2017-02-06 17:05:09 : vi ~/.bashrc 
  439  2017-02-06 17:14:46 : history

Linux: Change your hostname

A few different ways are possible to change your hostname in linux.

• With hostnamectl:

As root: 

[root@toolz ~]# hostnamectl set-hostname NEW-HOSTNAME

Then login/logout to see effects

Postgres: Install Postgresql-server 9.2 on Centos 7.2

• You search for the package you'll want to install
[root@toolz ~]# yum search postgres|grep server


• To get more details:
[root@toolz ~]# yum info postgresql-server.x86_64


• Then install it:
[root@toolz ~]# yum install postgresql-server.x86_64


• Setup the postgres password:
[root@toolz ~]# passwd postgres


• Init the postgres first DB
[root@toolz ~]# sudo postgresql-setup initdb


• Setup your connections:
[root@toolz ~]# sudo vi /var/lib/pgsql/data/pg_hba.conf


• Start postgresql service
[root@toolz ~]# systemctl start postgresql


• And finaly enable it to start automatically at next boot
[root@toolz ~]# systemctl enable postgresql

What to do next:

• pg_hba.conf
• create databases and users
• postgresql-server logging

Linux: apt

Common errors:

gpg: keyserver receive failed: No dirmngr

The error will look like:

root@deb15:~# apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0DF731E45CE24F27EEEB1450EFDC8610341D9410
Executing: /tmp/apt-key-gpghome.CQvyuFwlWI/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0DF731E45CE24F27EEEB1450EFDC8610341D9410
gpg: failed to start the dirmngr '/usr/bin/dirmngr': No such file or directory
gpg: connecting dirmngr at '/tmp/apt-key-gpghome.CQvyuFwlWI/S.dirmngr' failed: No such file or directory
gpg: keyserver receive failed: No dirmngr

To fix it, just install dirmngr:

root@deb15:~# apt install dirmngr

Now, all's fine:

root@deb15:~# apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0DF731E45CE24F27EEEB1450EFDC8610341D9410 Executing: /tmp/apt-key-gpghome.zspnEwdIk3/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0DF731E45CE24F27EEEB1450EFDC8610341D9410 gpg: key EFDC8610341D9410: public key "Spotify Public Repository Signing Key " imported gpg: Total number processed: 1 gpg: imported: 1

Linux: Create a bootable usb key

It's pretty simple and straight forward to create bootable USB on linux.

dd if=image.iso of=/dev/sdX bs=4M && sync

with:

• if: Input FIle (your ISO)
• of: Output File. /dev/sdX represent your USB key. Replace X with the letter of your volume (can be found with fdisk -l)
• bs: Block Size
• sync: make sure all data in buffer are written to disk 

Linux: Change your lost root password

Careful, this doesn't work on Centos 7

On startup, go to rescue mode. e to edit the line.

Add int=/bin/bash in the linux/kernel line (depending if you're using grub or grub2). Start it.
When on the command line, mount your file system and change your password:

# mount -o rw, remount /
# passwd
# touch / .autorelabel
# /sbin/reboot -f

Now, you have a new root password ;)