Remount read/write in single user mode
If /etc/fstab is correct, you can simply type: # mount -n -o remount / If /etc/fstab is wrong, you must give the device name and possibly the type, too: e.g. # mount -n -o remount -t ext4 /dev/sda3 /
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Pacemaker / Corosync / DRBD Cheatsheet
Monitor the status: crm_mon Migrate all resources to another node: crm resource migrate rg_main <fqdn_node_name> Take node offline and online (be careful, this sets a ‘prefer’ to the other node to force a transition, which may or may not get removed afterwards): crm node standby crm node online Start and stop all resources (warning, this […]
Exchange 2012 Allow Relay from IP
Enable mail relaying from a specific IP or range of IPs. 1. Exchange Management Console -> Server Configuration -> Hub Transport 2. New Receive Connector * Set remote network to the IP or range you want to allow relay from (default is any IP so watch out here) * “Externally Secured” authentication * “Exchange Servers” […]
Increasing max files or folders per directory on Linux EXT filesystem
If a (poorly coded) app reaches the maximum number of files or folders per directory in Linux, you may see errors like this: Error happened when generating Download Link. Please try again or Contact administrator. (ERROR:mkdir) A quick and dirty way to increase the limit (and overall performance of the system) is to add the […]
Reset Supermicro IPMI password with ipmitool
This will set the ‘ADMIN’ user password back to default of ‘ADMIN’. You could set it to anything you want, this is just an example. yum -y install ipmitool modprobe ipmi_devintf ipmitool -I open user set password 2 ADMIN
Strong Password Encryption in PHP
Don’t try to reinvent a complex and highly refined wheel, especially when customer data is involved. Please use phpass on any PHP project. (that’s PH-Pass) http://www.openwall.com/phpass/ Good reading for password hashing in general. http://www.openwall.com/articles/PHP-Users-Passwords
Cpanel Apache Symlink Protection
wget http://layer1.rack911.com/before_apache_make -O /scripts/before_apache_make chmod 700 /scripts/before_apache_make ## Rebuild apache (might want to do it thru WHM instead) /scripts/easyapache –build
AS Number Stats on Linux
I’ve got a couple of Linux machines that are sitting outside of the Sflow ‘zone’ and AS traffic stats go unmeasured. I wanted to get a rough idea on the number of connections per AS number so here’s a little app that parses netstat and sorts AS numbers by number of connection. NOTE1: This won’t […]
Obfuscate or Encrypt Perl
There are 3 primary options: 1. Use PAR with PAR::Filter::Obfuscate or PAR::Filter::Crypto 2. Use Filter::Crypto::CryptFile (requires certain modules installed on target system) 3. Encrypt modules with Module::Crypt.
Clone a live linux system with Rsync over SSH
Update: 5/3/17 — Add additional notes for CentOS7 (dracut + grub2) and XenServer targets All commands are run on new server. 1. Boot into rescue mode (iso, pxe, ect). 2. Create partitions with ‘fdisk /dev/sda’. Type 83 for non-RAID fs, 82 for swap, type fd in the case of RAID (all partitions). Flag boot partition […]