Linux
Contents
Distributions
Features
Common stuff
- Scripts to help with Nagios and server reboots - https://github.com/LaMi-/nagios_downtime
CentOS - max pids
To view the current maximum number
$ cat /proc/sys/kernel/pid_max 32768
To increase the maximum number of processes, you can use sysctl for a temporary or permanent change.
Temporarily update it (until next reboot):
# sysctl -w kernel.pid_max=1048576
or a permanent change:
# echo "kernel.pid_max = 1048576" >> /etc/sysctl.conf # sysctl -p
cPanel sets it to 1048576 by default.
Mount .img in directory
To mount a disk image in a directory.
# losetup -v --show -f /path/to/disk.img /dev/loop0 # mount -t ext3 /dev/loop0 /mnt
If disk.img is an image of the entire disk, not just a filesystem, you can specify
# fdisk -l /dev/loop0
Disk /dev/loop0: 4022 MB, 4022337024 bytes, 7856127 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/loop0p1 62 7849447 3924693 83 Linux
This gives the start byte count (62 * 512 = 31744) to use. Remove the original loopback device (-d)
# losetup -d /dev/loop0
Add the new loopback device but specify the offset into the file as 31744 bytes.
# losetup -v --show -f -o 31744 /path/to/disk.img /dev/loop0 # mount -t ext3 /dev/loop0 /mnt
Package repositories
If you need something more up to date than the standard CentOS packages, check EPEL (Extra Packages for Enterprise Linux) or IUS (Inline with Upstream Stable).
- PHP 7 - IUS
- git 2.x - IUS
- Nagios - EPEL
- Perl modules installed for system Perl - EPEL
With CentOS, the EPEL repository can be enabled with yum install epel-release but RHEL users need to download the rpm from the main EPEL webpage.
IUS package urls to install the repository
- https://rhel6.iuscommunity.org/ius-release.rpm
- https://rhel7.iuscommunity.org/ius-release.rpm
- https://centos6.iuscommunity.org/ius-release.rpm
- https://centos7.iuscommunity.org/ius-release.rpm
These can be installed with yum install $url
