When supporting systems you have inherited or in environments that have many different OS versions and distributions of Linux. There are times when you simply don’t know off hand what OS version or distribution the server you are logged into is.
Luckily there is a simple way to figure that out.
Ubuntu/Debian $ cat /etc/lsb-release DISTRIB_ID=Ubuntu DISTRIB_RELEASE=13.04 DISTRIB_CODENAME=raring DISTRIB_DESCRIPTION="Ubuntu 13.04" RedHat/CentOS/Oracle Linux # cat /etc/redhat-release Red Hat Enterprise Linux Server release 5 (Tikanga) Catchall If you are looking for a quick way and don’t care what the output looks like, you can simply do this as well.
Adding static routes in Linux can be troublesome, but also absolutely necessary depending on your network configuration. I call static routes troublesome because they can often be the cause of long troubleshooting sessions wondering why one server can’t connect to another.
This is especially true when dealing with teams that may not fully understand or know the remote servers IP configuration.
The Default Route Linux, like any other OS has a routing table that determines what is the next hop for every packet.
When it comes to package management on Red Hat based systems Yum (Yellowdog Updater, Modified) is my preferred method. It’s a quick and easy way of installing desired rpm’s and their dependencies as Yum will automatically resolve dependencies before installation.
Most Red Hat base distributions include a public facing Yum repository that you can configure yum to use in order to save from having to maintain a local copy of every package on each system.
Since I’ve mostly been using Red Hat or the gui desktop of Ubuntu lately I’ve neglected to notice the transitions from the sysVinit packages to systemd. Recently I installed Fedora 16 and was a little surprised when chkconfig didn’t work anymore. I decided I would write a post that gives the systemctl version of a few common chkconfig commands.
List processes chkconfig:
chkconfig –list systemd:
systemctl list-units Enable a service chkconfig:
Cron is a time based scheduled task daemon that runs on most common Unix/Linux distributions. Because cronjobs are time based sometimes it is necessary to validate that the job ran at the scheduled time. Sometimes people will configure a cron to send the output of the script to a user via system mail or redirect the output to a file; however not all crons are setup the same and many times they may be configured to send output to /dev/null hindering any ability to validate the job ran.
If you want to check what packages are installed on a debian based machine you can use dpkg.
slize:~# dpkg –list Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad) ||/ Name Version Description +++-=========================================== ii adduser 3.110 add and remove users and groups ii apache2 2.2.9-10+lenny7 Apache HTTP Server metapackage ii apache2-mpm-prefork 2.2.9-10+lenny7 Apache HTTP Server - traditional non-threaded model Or if you are looking for a specific package you can put the name after the command.