Notepad:Linux

Linux Tips and Tricks

Linux stuff I often have to lookup. Just my personal list of things.

• NFS unload filesystem
• mysql slave skip error
• GRUB install
• Domain Keys
• Change Timezone
• Gigabit Network
• Syncookie
• Local Mount
• SWAP
• depmod
• Chain of IP addresses
• Xterm startup with different colors and font sizes
• Notepad:RPM - YUM Platform
• In place upgrade of Fedora Core by yum
• CentOS / Red Hat Linux: Install and manage iSCSI Volume
• Configure a LDAP directory service
• NetworkManager Configuration
• Accessing IMAP email accounts using telnet.
• Enable service syslog to have /var/log/messages populated
• Force a disk check on reboot

shutdown -rF now

• Create a network bridge for Virtual Machines
• Upgrade CentOS 4 to 5
• Create a CRT for an SSL certificate
• Properly configure Samba on Linux
• Postfix config
• Use wget to download full website
• Converting a running physical machine to a kvm virtual machine
• Generate XAUTH on a new host

xauth add `hostname`/unix:0 . `openssl rand -hex 32`

• yum versionlock - allows to lock an rpm
• install faster random for dns etc.

 yum install haveged;
 systemctl enable haveged;
 systemctl start haveged

• How to modify an invalud sudoers file

sudo visudo -f /mnt/etc/sudoers

• Converting a running physical machine into a KVM virtual machine
• Which Process is listening on a port

netstat -tulpn

• Recover GRUB 2
• Install all package from another machine

xargs yum -y install < file

• Create Default Home Directory

mkhomedir_helper username

• Schedule crontab with lock
• Configure UPS shutdown frmo Linux with nut
• Midnight Commander
• Nagios
• Google Authenticator Setup
• Boot from Centos 7 RAID 1 EUFI
• Create a directory under var at boot or startup

use tmpfiles.d and have your package create at startup or boot a file or directory /usr/lib/tmpfiles.d/mydaemon.conf :
man tmpfiles.d

#Type Path            Mode UID      GID    Age Argument
d     /run/mydaemon   0755 myuser myuser   -   -

• lm_sensors
• Change systemd Timeout
• Google Authenticator Across Servers
• Yum install with missing deps

rpm -Uvh --nodeps $(repoquery --location <module>)

• Example routing iptables firewall
• Disable IPv6
• find the right device for smartctl
• ssh into a machine without a terminal -T
• Clean Out Journal

  sudo journalctl --vacuum-time=3weeks

• Reclaim disk space from a sparse image file (qcow2/ vmdk)
• Make your Raspberry Pi file system read-only
• Linux Multiple Interface NAT
• Get Ethernet Address of network (Exclude lo, virtual and ethernet)

  ip -br l | awk '$1 !~ "lo|vir|eth" { print $3 }'

IoT

• Generate Encoded Password for Netplan / network-config - use psk

  wpa_passphrase <ssid> [passphrase]

• Ubuntu stop pop-up for daemons for apt

Change the restart command in ```/etc/needrestart/needrestart.conf``` to 'i'

  sed "/#\$nrconf{restart} = 'i';/s/.*/\$nrconf{restart} = 'a';/" /etc/needrestart/needrestart.conf

• Create a user password hash to automatically add

  mkpasswd -m sha-512 PASSWORD [SALT]

• x86 Suppress message at boot

  /etc/default/grub
  GRUB_TIMEOUT_STYLE=hidden
  GRUB_HIDDEN_TIMEOUT_QUIET=true

  GRUB_CMDLINE_LINUX_DEFAULT="rhgb quiet rd.plymouth=0 plymouth.enable=0 --log-level=0 systemd.log_level=0 systemd.show_status=0" 

  grub2-mkconfig -o /boot/grub2/grub.cfg

• Raspberry Pi4 ubuntu suppress log at boot

  /boot/firmware/cmdline.txt
  (eliminate console=tty1)
  rd.plymouth=0 plymouth.enable=0 --log-level=0 systemd.log_level=0 systemd.show_status=0

LVM

LVM Expand

Expand the physical size

gparted

Expand the logical volume

lvextend -l +100%FREE /dev/vg.../lv....

Resize the file system

resize2fs /dev/vg.../lv...

LVM Snapshot

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