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:: TOC ::

Cron
Docker
IPMI
IPTABLES
LXC
Network
Resources/Misc
Visudo
ZFS

:: Update Server ::

https://help.ubuntu.com/lts/serverguide/installing-upgrading.html do-release-upgrade


:: Cron ::


:: Network ::

  • Hints

    • Do not mix ifconfig XX up with ifup XXX
    • If ifup is not working use --force
    • Handle service networking restart with care
    • Do not specify 2 or more gateways on the same interface
    • Shut down interfaces: sudo ip link set eth0 down
    • Remove virtual interface: ifconfig eth0:1 down
    • Good ifup, ifdown description: https://www.computerhope.com/unix/ifup.htm

  • NAT

  • Check state of interfaces
    cat /run/network/ifstate

  • List all network cards
    lspci | egrep -i --color 'network|ethernet'

  • Show all ip addresses
    ip addr show

  • Show interfaces and their name
    lshw -class network

  • Show/manipulate network interfaces
    cat /etc/network/interfaces

  • Check speed / connection of network cards
    ethtool <eth0>

  • Network class
    lshw -class network

  • Find active internet connections
    netstat -tulpen

  • Get names of interfaces
    ip link

  • Services listening on port
    lsof -nPi tcp:the-port

  • Monitor traffic
    nethogs <interface>

  • Port forwarding
    /etc/rc.local

  • Check speed between two servers

    • sudo apt-get install iperf
    • We'll start an iperf server on one of the machines:
      iperf -s
    • And then on the other computer, tell iperf to connect as a client:
      iperf -c <address of other computer>

  • Login problems via SSH
    Getting a pam_systemd(sshd:session): Failed to stat runtime dir: No such file or directory message: Added directory with user_id in /run/users/

  • Chaging DNS resolving

    • sudo nano /etc/resolvconf/resolv.conf.d/base
    • sudo resolvconf -u

  • Virtual networks
    https://en.wikipedia.org/wiki/Virtual_network
    https://linuxconfig.org/configuring-virtual-network-interfaces-in-linux

  • Reload an interface (e.g., after changing /etc/network/interfaces)
    sudo ifdown <interface> && sudo ifup <interface>
    sudo service networking restart


IPTABLES

  • List IPTABLES
    iptables -S
    iptables -L

  • IPTABLES Links
    https://help.ubuntu.com/community/IptablesHowTo

  • Portforwardings settings
    Rules are set in /etc/rc.local

  • Portforwarding: show current setup
    iptables -t nat -v -L -n --line-number

  • Portforwarding: set rule
    iptables -t nat -A PREROUTING -i br0 -p tcp -m tcp --dport PORT -m comment --comment "COMMENT" -j DNAT --to-destination xxx.xxx.xxx.xxx:PORT
    Example:
    iptables -t nat -A PREROUTING -i br0 -p tcp -m tcp --dport 10002 -m comment --comment "My-LXC" -j DNAT --to-destination 10.0.0.10:22

  • Portforwarding: Delete rule (use line number)
    https://www.cyberciti.biz/faq/how-to-iptables-delete-postrouting-rule/
    iptables -t nat -D PREROUTING 3

:: Disks ::

  • Display block devices
    blkid -o list

  • Display all disks 

parted
print all
  • Display all SCSI disks
    lsscsi -s


:: ZFS ::

  • List all zfs-folders/zfs-volumes
    zfs list

  • Status of zpool
    zpool status

  • Export zpool (unmount)
    zpool export <zpoolname>

  • Remove/destroy
    zpool destroy <zpoolname>

  • Show snapshots
    zfs list -t snapshot

  • Volumes 

zfs list -t volumes
Volumes are listed here: /dev/zvol/tank/


:: Docker ::

docker run 
-d         detach
--name     Name of the container
--restart  Automatically restart the container -  no, always
-p         Ports
-v         Bind a volume

creates and starts a container

sudo nano /lib/systemd/system/docker.service Add the dns after ExecStar. --dns 10.252.252.252 --dns 10.253.253.253 Should look like that: ExecStart=/usr/bin/dockerd -H fd:// --dns 10.252.252.252 --dns 10.253.253.253

systemctl daemon-reload
sudo service docker restart

1) stop the container 
2) change the file /var/lib/docker/containers/[hash_of_the_container]/hostconfig.json
3) restart your docker engine (to flush/clear config caches)
4) start the container
  • Problem restarting with network issue
docker network ls
docker network disconnect -f <networkname>
docker network rm <networkname>

moby/moby#20398

:: IPMI ::

https://www.thomas-krenn.com/de/wiki/IPMI_Grundlagen https://help.ubuntu.com/community/IPMI https://www.thomas-krenn.com/de/wiki/IPMI_Konfiguration_f%C3%BCr_Supermicro_Systeme https://www.thomas-krenn.com/de/wiki/Softwaretools_f%C3%BCr_IPMI_im_%C3%9Cberblick

  • Read the SEL - system error log: ipmitool sel list

  • Clear the SEL ipmitool sel clear

:: Switch ::

Dell 5500

"Although they can work in small EQL (and other iSCSI) SAN networks they should be seen as campus-access switches and not as SAN switches." https://en.wikipedia.org/wiki/Dell_PowerConnect#5500_series


:: KVM ::

kvm list machines: virsh list --all
kvm shutdown: virsh shutdown vm-name
kvm shutdown: connect to the machine via ssh and type "init 0"
kvm start: virsh start vm-name


:: LXC ::

lxc-stop -n $NAME
cd /var/lib/lxc
tar --numeric-owner -czvf container_fs.tar.gz $NAME
rsync -avh container_fs.tar.gz user@newserver:/var/lib/lxc/
rsync -avPrh -e "ssh -p 10009" folder user@SERVER:/DEST/

:: Services ::

  • List all running services
    service --status-all


:: Visudo ::

sudo visudo Be aware that adding a user to the sudo group overrides the entries in sudoers

:: SSH ::

https://help.ubuntu.com/lts/serverguide/openssh-server.html


:: Resources / Misc ::

:: RSYNC ::

  • Use only limited bandwith:
    rsync --bwlimit=<kb/second> <source> <dest>

:: Useful information ::

  1. Move to the previous directory - We all use cd .. to move to move to an upper directory. You can also use cd - to move to the previous directory - just like a back button.
test@linoxide:~/Downloads$ cd -
 /home/xy
test@linoxide:~$ cd -
 /home/xy/Downloads
  1. Repeat your last command - To replay as the previous command, just type !!
$ apt install vlc
 E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)
$ sudo !!
 sudo apt install vlc
  1. Keep executing a command until it succeeds - use the exit code of the command directly. The command kept running until it found run.sh and printed out its content.
$ while ! ./run.sh; do sleep 1; done
cat: run.sh: No such file or directory
linoxide.com
  1. View progress of file transfers In Linux, you cannot really know the rate of a file transfer progress until it's done. Using the pv command, you can monitor the progress of file transfers.
$ pv access.log | gzip > access.log.gz
 611MB 0:00:11 [58.3MB/s] [=> ] 15% ETA 0:00:59
  1. Easily schedule events Using the at command, you can easily schedule events at anytime.
echo wget https://sample.site/test.mp4 | at 2:00 PM
To view the queued jobs, type 
atq
  1. Display at output as a table When you use the ls command or other commands to throw outputs, they are often very long and need scrolling. You can easily display all the outputs in a table form using the column -t command.
$ cat /etc/passwd | column -t
  1. Keyboard Tricks
  • The clear command clears the terminal screen with a blank one. Pressing Ctrl + L on your keyboard does the same thing, but faster.
  • To go through previous commands, press Alt + . .
  • Ctrl + U clears the content you've typed already. Try this when you want to clear the password field in the command line.
  • To reverse search your command history, press Ctrl + R
  1. Compress, split and encrypt files Trying to transfer large files across computers is a tedious task. We can easily do this by compressing the files and creating a multi-part archive if the files are extremely large. To encrypt, we add the -e switch.
$ zip -re test.zip AdbeRdr11010_en_US.exe run.sh Smart_Switch_pc_setup.exe
 Enter password:
 Verify password:
 adding: AdbeRdr11010_en_US.exe (deflated 0%)
 adding: run.sh (stored 0%)
 adding: Smart_Switch_pc_setup.exe (deflated 2%)
  1. Stress test your battery - Try this command:
$ cat /dev/urandom > /dev/null
  1. Renaming/moving files with suffixes - If you want to quickly rename or move a bunch of files with suffix, try this command.
$ cp /home/sample.txt{,-old}
This will translate to:
$ cp /home/sample.txt /home/sample.txt-old
To rename files of a particular extension in batch, try this:
$ rename 's/comes_here_/goes_there/' *.txt

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