Most of the commands will be CentOS/RHEL related since that comes across my screen the most often. Hopefully others will find this stuff useful as well.
And a quick shout out to a few of the sites that have provided invaluable help in the last few years, thanks so much for saving my bacon!
All commands are listed as if run by root, rather than prefix everything requiring elevated access with sudo. Variables are in red italics for easy recognition.
Vi Cheat Sheet
Shell Scripting Cmd Arguments
Vi Cheat Sheet
Shell Scripting Cmd Arguments
Commands:
Disabling selinux# vi /etc/selinux/config
SELINUX=permissive
# reboot
Add date stamps to History cmd
# HISTTIMEFORMAT="%d/%m/%y %T "
Add it permanently...
# echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> ~/.bash_profile
Software management using Yum
# yum -y install mlocate
# yum search ifconfig (search for pkg, helps when app is part of a larger install)
# yum whatprovides ifconfig (search for pkg, helps when app is part of a larger install)
# yum erease telnet
# yum list q* (list installed pkgs that start with q)
Software management using RPM
# rpm -ivh cool-pkg-1.2-3.el7.x86_64.rpm (-i installs a pkg, v=verbose, h=hashes for progress)
# rpm -Uvh cool-pkg-1.2-3.el7.x86_64.rpm (-U upgrades)
# rpm -e cool-pkg-1.2-3.el7.x86_64.rpm (-e uninstalls/erases)
# rpm -qa | grep cool-pkg (-qa lists installed packages, while grep (optional), search through results)
List files and directories, and sort by Size
# yum whatprovides ifconfig (search for pkg, helps when app is part of a larger install)
# yum erease telnet
# yum list q* (list installed pkgs that start with q)
Software management using RPM
# rpm -ivh cool-pkg-1.2-3.el7.x86_64.rpm (-i installs a pkg, v=verbose, h=hashes for progress)
# rpm -Uvh cool-pkg-1.2-3.el7.x86_64.rpm (-U upgrades)
# rpm -e cool-pkg-1.2-3.el7.x86_64.rpm (-e uninstalls/erases)
# rpm -qa | grep cool-pkg (-qa lists installed packages, while grep (optional), search through results)
List files and directories, and sort by Size
# ll –hSr
List files and directories with Year
# ll --full-time
Unpacking a tar.gz file
# tar -xzf cool-pkg.tar.gz (-x expands the file, -z unzips gzip files, -f specifies which file (must be last))
List files and directories with Year
# ll --full-time
Unpacking a tar.gz file
# tar -xzf cool-pkg.tar.gz (-x expands the file, -z unzips gzip files, -f specifies which file (must be last))
Rerun a command
# !!
Changing Directory
# cd ~ (current user's home directory)
# cd - (back to last directory)
Save previous cmd as a Script
# echo “!!” > script.sh
Managing Services (CentOS7/RHEL7)
# systemctl list-unit-files (list services and status)
# chkconfig --list (lists older services)
# chkconfig --list | grep 3:on (lists older services that start with runlevel 3)
# systemctl enable snmpd.service (for auto-start)
# systemctl start snmpd.service (start/stop/reload/restart)
Managing Services (CentOS/RHEL 5&6)
# chkconfig --list (lists all services)
# chkconfig --list | grep 3:on (lists services that start with runlevel 3)
# chkconfig network on or off (for auto-start setting)
# service network start (stop/restart/reload)
Repair XFS
# xfs_repair -L /dev/mapper/centos-root
Drive Health Cmds
# smartctl -H /dev/sda
# badblocks -b 512 -s /dev/sda
Network Speed
# ethtool eth0 (em1, p1p2, etc.)
Determine DHCP Server Info
# cat /var/lib/dhcp/dhclient.eth0.leases
Install IP Command Missing from RHEL Distro
Determine DHCP Server Info
# cat /var/lib/dhcp/dhclient.eth0.leases
Install IP Command Missing from RHEL Distro
# yum -y install iproute
Finding your extrnal IP at the cmd line
# dig +short myip.opendns.com @resolver1.opendns.com
or
# host myip.opendns.com resolver1.opendns.com | grep "myip.opendns.com has" | awk '{print $4}'
# dig +short myip.opendns.com @resolver1.opendns.com
or
# host myip.opendns.com resolver1.opendns.com | grep "myip.opendns.com has" | awk '{print $4}'
or
#wget -qO- http://ipecho.net/plain | xargs echo
Using NetworkManager at the cmd line (NetworkManager service must be running)
# nmtui
Disabling NetworkManager (allows direct editing of ifcfg-eth0 files)
# systemctl stop NetworkManager.service
# systemctl disable NetworkManager.service
# systemctl enable network.service
# systemctl start network.service
# reboot
Managing Firewall in RHEL/CentOS 7
See what's being allowed through:
# firewall-cmd --list-services
# firewall-cmd --list-ports
# firewall-cmd --list-all
List current zone(s): default is public
# firewall-cmd --get-active-zones
Adding access to a specific zone:
# firewall-cmd --permanent --zone=public --add-port=2888/tcp
# firewall-cmd --permanent --zone=public --add-service=http
Or all zones:
# firewall-cmd --add-port=132/tcp --permanent
# firewall-cmd --add-services=ntp
To make the changes active:
#firewall-cmd --reload
Show mounted file systems
# mount -l
# mount -l -t ext4 (-t designates type, i.e. xfs, nfs4, etc.)
#wget -qO- http://ipecho.net/plain | xargs echo
Using NetworkManager at the cmd line (NetworkManager service must be running)
# nmtui
Disabling NetworkManager (allows direct editing of ifcfg-eth0 files)
# systemctl stop NetworkManager.service
# systemctl disable NetworkManager.service
# systemctl enable network.service
# systemctl start network.service
# reboot
Managing Firewall in RHEL/CentOS 7
See what's being allowed through:
# firewall-cmd --list-services
# firewall-cmd --list-ports
# firewall-cmd --list-all
List current zone(s): default is public
# firewall-cmd --get-active-zones
Adding access to a specific zone:
# firewall-cmd --permanent --zone=public --add-port=2888/tcp
# firewall-cmd --permanent --zone=public --add-service=http
Or all zones:
# firewall-cmd --add-port=132/tcp --permanent
# firewall-cmd --add-services=ntp
To make the changes active:
#firewall-cmd --reload
# mount -l
# mount -l -t ext4 (-t designates type, i.e. xfs, nfs4, etc.)
Reload the NFS exports after changing /etc/exports
# exportfs -ra
Unmounting NFS share
# umount /builds
Finding iDRAC/iLO Address
# modprobe ipmi_si; ipmitool lan print
Set iDRAC/iLO to DHCP
# ipmitool lan set 1 ipsrc dhcp
Changing an iDRAC/iLO IP Address
Set iDRAC/iLO to DHCP
# ipmitool lan set 1 ipsrc dhcp
Changing an iDRAC/iLO IP Address
# ipmitool lan set 1 ipsrc static (if it is currently DHCP)
# ipmitool lan set 1 ipaddr 172.23.126.188
# ipmitool bmc reset cold (restarts IPMI HW)
Even more IPMI info
Uninstalling ipmitool and components (in case you had to install it temporarily)
# yum -y erase ipmitool OpenIPMI net-snmp-libs OpenIPMI-libs OpenIPMI-modalias
# ipmitool lan set 1 ipaddr 172.23.126.188
# ipmitool bmc reset cold (restarts IPMI HW)
Even more IPMI info
Uninstalling ipmitool and components (in case you had to install it temporarily)
# yum -y erase ipmitool OpenIPMI net-snmp-libs OpenIPMI-libs OpenIPMI-modalias
List version of Red Hat/Fedora/CentOS
# cat /etc/redhat-release
List version of SuSE
# cat /etc/SuSE-release
List verion of Ubuntu
# cat /etc/lsb-release
List verion of Debian
# cat /etc/debian_version
Kernel info
# uname -a
View network info
# ifconfig or # ip addr
Add an IPv6 address
# /sbin/ip -6 addr add fd63:6f75:6368:20d3:ac3c:257e:9c5:6619/64 dev eth0
Add an IPv6 address
# /sbin/ip -6 addr add fd63:6f75:6368:20d3:ac3c:257e:9c5:6619/64 dev eth0
DNS servers (also may be in /etc/sysconfig/network-scripts/ifcg-eth0)
# cat /etc/resolv.conf
Hostname and Gateway
# cat /etc/sysconfig/network
Set hostname in RHEL/CentOS 7
# hostnamectl set-hostname yourcoolhostname
Set hostname in RHEL/CentOS 7
# hostnamectl set-hostname yourcoolhostname
Shell being used
# echo $SHELL
List cron jobs (scheduled tasks)
# crontab -l (-e to edit)
Motherboard Info
# dmidecode -t 2
CPU Information
# dmidecode -t 2
CPU Information
# cat /proc/cpuinfo
Amount of Memory
# cat /proc/meminfo
Mounted filesystems (in MB/GB)
# df -h
Check PCI Buses and Devices
# lspci
Check USB Buses and Devices
# lsusb
Crazy amount of Hardware Data
# dmesg | less
or
# lshw
or
# lshw
Show a list of recent logins
# last (-F will also list year, only works with newer OSes)
Process list (check out additional switches)
# ps -A
# ps aux | grep program (search for running processes by name)
Current performance and PIDs (you can use kill to end a runaway process)
# top
Stop a runaway process
# kill -9 32440 (get process number from using top)
Current memory usage (in MB/GB)
# free -h
Disk usage (directories by size, based on your current location, usually best to start from root /)
# du -sh *
Single directory
# du -sh /some/dir
Check type of filesystem
# file -sL /dev/sd*
Network status (lots of switches to drill down with)
# file -sL /dev/sd*
Network status (lots of switches to drill down with)
# netstat -a
Time since last Reboot
# uptime
Searching for text within a file, or files, throughout the OS
# grep -Ril "text-to-find-here" /
-R recursive
-i ignores case
-l show file name
Finding a file
# find / -name "filename" (searches the whole file system)
or
# find -name "filename" (will search just the current directory)
Find disk to add, i.e. /dev/sdb
# fdisk -l
Select disk to edit
# fdisk /dev/sdb
Add a partition
: n (for new)
: p (for primary partition)
: 1 (partition #)
: w (write changes & exit)
Format the new partition (here you can choose xfs, ext3, etc.)
# mkfs -t ext4 /dev/sdb1
Add a mount point
# mkdir /data
Add to /etc/fstab
# /dev/sdb1 /data ext4 defaults 0 0
Mount the new drive
# mount -a
Mounting a new drive over 2TB:
Find disk to add, i.e. /dev/sdb
# fdisk -l
Use Parted to setup the disk
# parted /dev/sdb
(parted) mklabel gpt (answer yes to the warning)
(parted) unit TB
(parted) mkpart primary 0.00TB 3.5TB
(parted) print
(parted) quit
Format the new partition (here you can choose xfs, ext3, etc.)
# mkfs -t ext4 /dev/sdb1
Add a mount point
# mkdir /data
Add to /etc/fstab
# /dev/sdb1 /data ext4 defaults 0 0
Mount the new drive
# mount -a
Increasing an LVM partition (after some work with Volume & Logical Groups)
# resize2fs or #xfs_growfs
Wiping the password in Single User Mode (useful for CentOS/RHEL6)
# passwd -d root
Searching for text within a file, or files, throughout the OS
# grep -Ril "text-to-find-here" /
-R recursive
-i ignores case
-l show file name
Finding a file
# find / -name "filename" (searches the whole file system)
or
# find -name "filename" (will search just the current directory)
Change Default GRUB2 Entry
List entries
# grep "^menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
Change the default boot selection
# grub2-set-default 1 (the list starts with 0)
Confirm the change
# grub2-editenv list
Save settings
# grub2-mkconfig -o /boot/grub2/grub.cfg
Mounting a new drive:List entries
# grep "^menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
Change the default boot selection
# grub2-set-default 1 (the list starts with 0)
Confirm the change
# grub2-editenv list
Save settings
# grub2-mkconfig -o /boot/grub2/grub.cfg
Find disk to add, i.e. /dev/sdb
# fdisk -l
Select disk to edit
# fdisk /dev/sdb
Add a partition
: n (for new)
: p (for primary partition)
: 1 (partition #)
: w (write changes & exit)
Format the new partition (here you can choose xfs, ext3, etc.)
# mkfs -t ext4 /dev/sdb1
Add a mount point
# mkdir /data
Add to /etc/fstab
# /dev/sdb1 /data ext4 defaults 0 0
Mount the new drive
# mount -a
Mounting a new drive over 2TB:
Find disk to add, i.e. /dev/sdb
# fdisk -l
Use Parted to setup the disk
# parted /dev/sdb
(parted) mklabel gpt (answer yes to the warning)
(parted) unit TB
(parted) mkpart primary 0.00TB 3.5TB
(parted) print
(parted) quit
Format the new partition (here you can choose xfs, ext3, etc.)
# mkfs -t ext4 /dev/sdb1
Add a mount point
# mkdir /data
Add to /etc/fstab
# /dev/sdb1 /data ext4 defaults 0 0
Mount the new drive
# mount -a
Increasing an LVM partition (after some work with Volume & Logical Groups)
# resize2fs or #xfs_growfs
Wiping the password in Single User Mode (useful for CentOS/RHEL6)
# passwd -d root
Single user mode in Ubuntu
1. Interrupt boot and click "e" to edit the GRUB config
2. Add 1 to the end of the linux statement
3. Press Ctrl+x to start the system
Enable Root Login on Ubuntu
(Login as standard user)
$ sudo su -
# passwd
# sed -i 's/prohibit-password/yes/' /etc/ssh/sshd_config
# systemctl restart sshd
Sample Ubuntu /etc/network/interfaces file
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto eth0 (makes the interface start with the OS)
iface eth0 inet static
address 172.16.1.25
netmask 255.255.255.0
gateway 172.16.1.1
dns-nameservers 172.16.0.11 10.250.1.12
# ifdown eth0 && sudo ifup eth0 (to make change, service networking restart often fails)
# /etc/init.d/networking restart (may also work)
Sample Netplan Configuration /etc/netplan/01-netcfg.yaml file
network:
version: 2
renderer: networkd
ethernets:
eth0:
dhcp4: no
addresses: [172.16.1.55/24]
gateway4: 172.16.1.1
nameservers:
addresses: [8.8.8.8,4.4.4.4]
Test the config with # netplan try and confirm with # netplan apply
Misc. notes:
Add a space before a command to omit from history
Perform a command repeatedly over a range of systems (x is variable , {range of #'s}, do cmd)
for x in 172.16.125.{29..73};do ping -c 1 $x; done (this pings 172.16.125.29 thru .73)
Postfix
Defaut config location: /etc/postfix/main.cf
Check mail queue
# mailq
Flush mail queue
# postqueue -f
Restart Postfix
# postfix reload
List non-default config items
# postconf -n
Python
Installing Python 3.8.x on Ubuntu
1. Install Prerequisites
# apt-get install build-essential checkinstall
# apt-get install libreadline-gplv2-dev libncursesw5-dev libssl-dev libsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev
2. Download and extract Python 3.x.x (latest was 3.8.0a2 at time of writing)
# cd /usr/src
# wget https://www.python.org/ftp/python/3.8.0/Python-3.8.0a2.tgz
# tar xzf Python-3.8.0a2.tgz
3. Installing Python
# cd Python-3.8.0a2
# ./configure --enable-optimizations
To keep it from replacing the default python binary
# make altinstall
4. Check and confirm version
# python3.8 -V
Postfix
Defaut config location: /etc/postfix/main.cf
Check mail queue
# mailq
Flush mail queue
# postqueue -f
Restart Postfix
# postfix reload
List non-default config items
# postconf -n
Python
Installing Python 3.8.x on Ubuntu
1. Install Prerequisites
# apt-get install build-essential checkinstall
# apt-get install libreadline-gplv2-dev libncursesw5-dev libssl-dev libsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev
2. Download and extract Python 3.x.x (latest was 3.8.0a2 at time of writing)
# cd /usr/src
# wget https://www.python.org/ftp/python/3.8.0/Python-3.8.0a2.tgz
# tar xzf Python-3.8.0a2.tgz
3. Installing Python
# cd Python-3.8.0a2
# ./configure --enable-optimizations
To keep it from replacing the default python binary
# make altinstall
4. Check and confirm version
# python3.8 -V
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