Linux
CentOS 4
Creating Custom Kernel RPMs
(Note: may not be relevant to CentOS-4, I stuck this here because the dates (2008) kinda lined up...
Dovecott: Internal Login Failure
Problem # telnet localhost 110 Trying 127.0.0.1… Connected to localhost.localdomain (127.0.0.1). ...
End Of Life Repository Access
(7 August 2012) Problem Running a yum operation on CentOS 4, I get the error: not using ftp, http...
I2O RAID Controller
Problem You has some variety of the Adaptec 2010s RAID SCSI controller installed. Solution CentOS...
NFS Support
Installing ntfs support for CentOS RedHat and CentOS do not include ntfs, possibly for legal reas...
Permitting rdate access
Letting rdate work from other machines # chkconfig time-stream on Add a rule to /etc/sysconfig/i...
SCSI Device Names And Bus IDs
Problem (Asked on SuperUser.com) I have a CentOS 4.x server running software raid. The server has...
Updating to PHP 5
Problem I have a user who wants PHP 5 on our server. Solution This is a horrible problem. Advice ...
CentOS 5
rssh
Jailing sftp/scp connections (1206.12) Short notes: this uses the rssh functionality from rpmforg...
Building Subversion 1.85
(2014-01-16) Problem I want to run Subversion v1.85, client and server, on CentOS 5 (today's vict...
kickstart POST nfs mount
Mounting nfs file systems in the %POST section of a CentOS 5 kickstart mount 172.20.0.1:/home /mn...
NFS File Creation Cache Problems
Problem If I create a file on an nfs-mounted filesystem on one machine, the file may not be immed...
NVidia Multihead
Problem I am running a CentOS 5.3 x86_64 (fully updated as of today). It has a video card I canno...
Process Accounting
(26 September 2012) Process Accounting # chkconfig psacct on; service psacct start This will cre...
Remote X Display
Displaying Remote X Applications On Your Local Display ...ie, connect to a remote machine, run th...
SCSI Bus Rescan
(2014-03-24) Problem You've hot-added a new disk and now want to use it without rebooting. Soluti...
SquirrelMail: Users Can't Log In
(14 October 2012) Problem I have SquirrelMail version 1.4.8-5.el5.centos.13. When users attempt t...
SSL Certificate Warning
(2014-01-20) Problem Email: ################# SSL Certificate Warning ################ Certifi...
TCP Window Scaling
(5 November 2012) Problem: When sending mail to a particular target, we were unable to send messa...
Unexpected CUPS dependencies
(or, isn't RPM supposed to handle this kind of crap?) Error: Filter "foomatic-rip" for printer (s...
X Display Through SSH
(2014-03-24) Problem I ssh into a remote host and the $DISPLAY variable isn't set. Solution # yum...
Yum barf when updating package 'file'
Problem [dave@centos5-dave ~]$ sudo yum update file Loaded plugins: fastestmirror Loading mirror ...
CentOS 6
0x80070035 the network path was not found
(2013-06-03) Problem Trying to browse to a samba server by name from a Windows system yields the ...
bind always returns SERVFAIL
(2013-04-16) Problem I have installed a bind instance from RPM and all it does is SERVFAIL. Debug...
Client nis Setup
(2019-03-25) NIS client setup cookbook #!/bin/bash DOMAIN=my.nis.domain SERVERNAME=server4.my.ni...
Disable IPv6
(2014-09-16) Problem Things are slow. In our case, attempting to mount a previously-umounted file...
Dummy Cert Expired
Problem I'm getting messages that say: ################# SSL Certificate Warning ################...
Firefox Java Plugin
Yeah, 2015 and this isn't a solved problem. Problem Java in Firefox. CentOS 6.6, 64-bit. Solution...
Force NFS v3 Mounts
(2014-07-17) Problem My CentOS 6 client is trying to mount everything using NFS v4 and I want it ...
Ignore Host-ID
(2014-06-26) Problem I want to ignore the host-ID on connection for ssh. Yes, I know it is a dumb...
Install VMware Tools Yum Repository
(2014-01-14) Install VMware tools into a new Linux VM with a repository that will keep them updat...
Kickstart Ethernet Devices
(2014-02-17) Problem the specified interface eth0 does not exist Solution In the general case, sp...
Leap Second
Problem My nasty java app is eating up all the CPU it can get. (Possibly sharing with something e...
Minimal Install Can't Mount NFS Homedirs
(2014-05-13) Problem Install with @Base and @Core, plus ypbind and autofs. But once configured, t...
mod_fastcgi
(2016-02-24) Solution Fastcgi is available through RPMforge. To add the module: Install RPMforg...
netdisco-1.1-1.el6.noarch
(2013-05-29) How I Got NetDisco netdisco-1.1-1.el6.noarch Running On CentOS 6 From epel-testing: ...
nfs v4: Nobody Ownership
(21 January 2013) Problem When I look at the files exported from my CentOS 6 server, everything's...
Remove Host ID
(2014-06-26) Problem Host-ID has changed and ssh is complaining about it. Solution Shell alias: #...
Revert To eth Device Names
(2014-05-05) Problem: I have a piece of software that expects my first ethernet device to be call...
Samba full_audit
(2016-11-07) Problem I'd like to log activity that my samba server is doing. Solution CentOS 6 Sa...
SElinux SSH Pubkey Bug
(14 February 2013) Problem CentOS 6 is not accepting pubkey login attempts. Solution SElinux has ...
slow ssh connections
(26 October 2012) Problem When I ssh login to a CentOS 6 system, it always takes around 30 second...
VM Optimizations
(2014-01-14) This is all heavily based on  Configuring Winbind On A Fresh CentOS 6 Installation With this example, AD users in ...
ypbind won't bind to anything
(2014-06-16) Problem I have a CentOS 6 NIS master server that won't ypbind to anything. I have a ...
makeinfo build error
2013-05-15 Problem Building gcc 4.1.2 on CentOS 6 halts with the error: WARNING: `makeinfo' is mi...
CentOS 7
Active Directory with SSSD
(2021-02-03) Rough Notes install realmd # realm discover # realm join zoneName -U adminUser i...
arp
(2016-11-22) Problem arp -a is too brief. In keeping with the new trend of banging in long comman...
Auto SSH Agent
(2019-09-04) Notes that probably won't make any sense to anyone other than myself. This is border...
DSA SSH Hostkeys
(2017-05-25) Problem I have a stone-age host monitor thing that is complaining that it can't find...
Get Sendmail To Listen On 25, 425, and 587
(2017-05-03) Problem I want one sendmail.cf to control access to port 25 (no auth, access rules o...
grub parameters
(2017-09-13) Changing Grub Parameters With Grubby for KERNEL in /boot/vmlinuz-*; do grubby --...
hostname
(2016-11-21) Problem Setting the computer's hostname hasn't changed for the last 20 years or so. ...
Install Grub
(2018-08-21) Problem RHEL 7 doesn't have "grub" command for making RAID-1 disks bootable. Alleged...
journalctl
(2019-09-11) Examples # journalctl -u vmtoolsd --since=today # journalctl -u sshd
Passwordless SSH On NFS Home Dirs
(2017-04-28) Problem Can't use passwordless ssh to a target system. Solution In this particular c...
PHP 7
(2021-02-23) Installing PHP 7 Instructions for7.4 Older information (2017-09-13) CentOS 7 provide...
slow ssh connections
(5 September 2019) Problem When I ssh login to a CentOS 7 system, it always takes around 30 secon...
SSH no matching cypher
(2019-03-15) Problem Unable to negotiate with $IP port 22: no matching cipher found. Their offer:...
SSL Certificate Warning
(2014-01-20) Problem Email: ################# SSL Certificate Warning ################ Certifi...
Start Interface With No IP Address
(2018-06-19) Problem I want a network interface on my CentOS 7 system to start at boot time but I...
systemd
God Damnit What How List services systemctl list-unit-files Start service at boot time s...
Test Sendmail TLS Certificate
(2017-05-04) Problem Test Sendmail's TLS configuration. Solution $ openssl s_client -starttls smt...
tftp-server
(2018-01-12) Problem I need a tftp server on CentOS 7. Solution # yum -y install tftp-server xine...
Unban IP Address
(2017-05-06) Solution # fail2ban-client set sshd unbanip a.b.c.d
VM Interface Bouncing
(2019-09-13) Problem VM transplanted between two VMware clusters. Ran fine in old cluster for two...
vsftp: 500 OOPS: chroot
Problem vsftpd in user chroot mode. When logging in, you get: 500 OOPS: chroot Solution You have...
CentOS 8
docker
(2020-05-03) Docker on CentOS 8 # dnf config-manager --add-repo=https://download.docker.com/linux...
failed to load driver: swrast
(2021-08-17) Problem: Some variety of libGL error: MESA-LOADER: failed to open swrast: /usr/lib64...
Find Transparent Proxy Systems
(2021-02-17) Problem A system between me and my destination is doing proxying for the destination...
Installing From The Vault
(2022-02-01) Problem # sudo dnf (operation) Error: Failed to download metadata for repo 'appstrea...
Unifi Controller
Installing Unifi Controller on Docker on CentOS 8 (or probably any docker installation at this po...
Debian 8
(AKA: Debian Jesse)
sudo without password
(2017-05-30) Problem I don't want to get prompted for sudo access. Solution Run visudo At the...
Hyper-V Integration
(2015-02-18) Problem Jessie not fully integrated with Hyper-V out of the box. Solution /usr/bin/h...
Veeam Connection Error
(2016-02-19) Problem Veeam can't connect to the target Debian server, fails with: Server does not...
Fedora 31
Create A New lvm Partition
If you need to put more physical disk into the physical volume, do that: # vgextend fedora /dev/s...
KVM Bridge Interface
(2020-02-11) Creating A Bridge Interface for KVM VMs # nmcli connection add type bridge autoconne...
KVM, briefly
(2020-03-13) KVM Briefly # virsh list # virsh list --all # virsh start <name> # virsh dominfo <na...
KVM Installation
(2020-02-11) Installing KVM (These instructions assume the FC 31 environment.) # dnf -y install b...
KVM: virt-install
(2020-03-14) Installing a VM This example creates a 1c, 2GB VM with a 20GB disk, booting a kernel...
Fedora 32
Fedora 34
Add IP Information To issue File
Script: #!/bin/bash IP=${1:-`hostname -I`} # Add "IP ADDRESS" line if not already found grep "IP ...
Fedora Upgrade Procedure
(2022-02-08) Problem I want to upgrade from Fedora 34 to Fedora 35. Solution dnf -y --refresh upg...
Permanent Static Routing
(2021-06-15) Problem How do we set a static route entry to take effect at boot time without custo...
SSH Pubkey doesn't work
(2021-05-26) Problem userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth] ...
Test TLS version
(2021-10-06) Problem Does this device support TLS v1.0 (or 1.1 or 1.2 or 1.3) Solution $ openssl ...
VM under VMWare Player won't resize screen on drag
Problem A VM running under VMWare Player won't dynamically resize the "screen" on drag or full-sc...
Fedora 33
Fedora 35
Fedora 25
firewalld
(2016-12-06) God help me, this is firewalld After you make a change, reload the firewall to make ...
Install nfsen 1.3.6p1
(2016-12-02) Problem How do I get nfsen 1.3.6p1 running on Fedora Server 25? Disclaimer Works for...
Starting httpd
Problem How do I start up httpd in this brave new systemd world? Solution Firewall (note your zon...
Fedora 27
PPTP VPN Client
(2018-04-30) Setting A PPTP VPN Client You have to set the firewall to accept GRE tunnel traffic:...
Example nmcli Commands
(2018-10-15) Problem nmcli Solution Some recently discovered examples: # nmcli con # nmcli con s...
Firewalld Limit Remote Source Connections
(2019-02-14) Problem I have an internet-facing service that I want to restrict to a particular (s...
Fedora 30
Join AD
(2019-11-28) Problem # realm -v -U dave join mydomain.local [...] ! Couldn't create computer acc...
Samba AD Controller Notes
(2019-11-25) Backplot At a new customer site, I inherited a Active Domain that was hosted on a Sa...
Set Hostname To VM Name
(2019-11-28) Problem /t Solution For whatever reason, the vmware-tools package (and the open-vm-t...
Upgrading Fedora
(2019-03-18) Problem I want to update Fedora to another version. In General It is recommended to ...