16 Linux server monitoring commands you really need to know | Hacker News Reader

16 Linux server monitoring commands you really need to know

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33 pointsCrankyBear17 comments

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This is a terrible article which doesn't even meet the requirements for posting to hackernews.

Starts by assuming that runlevels mean the same thing on all Linux variants.

Yeah... a buzzfeed style inbound marketing post asking me to modify my runlevel. What could go wrong?

Welcome to the modern world, where knowing what a run level IS, let alone know how to USE one, matters.

What could go wrong? You forget to try to understand the question: what is my run level?

Exactly what an ephemeral DO vps is good for!

Worse still, it starts by assuming runlevels still have a meaning. Nearly all modern distro's are now running systemd, which has no notion of runlevels (targets are kind of the same but also very different!)

For reference, https://wiki.archlinux.org/index.php/Systemd#Targets is a nice little summary of how it's usually done these days.

The newest distros use systemd, but IT departments seldom run the newest distros on servers. For example, AWS's Linux AWI still doesn't have systemd support.

In several cases, the versions that preceded them ran upstart. Advice that has a blanket assumption of the presence of van Smoorenburg init has been wrong for longer than systemd has been around.

netstat is deprecated on Linux, ss should be used instead. Learning the differences is a good exercise by itself

htop may be better than top

I find when a server is close to using max CPU or mem, htop requires a surprising amount of resources that result in it lagging quite a bit.

I prefer htop.

I know install glances and use it in place of htop on all servers. Much more info and more customizable than htop.

It seems that a lot of distributions have moved to systemd - do runlevels and inittab even have any meaning for a systemd-based distribution?

They have a meaning, but the systemd people describe them as "obsolete".

* http://jdebp.eu./FGA/inittab-is-history.html

* http://unix.stackexchange.com/a/204075/5132

* http://unix.stackexchange.com/a/196014/5132

Not really. systemd uses targets (see the link to the Arch wiki from rhblake, above [1]) instead which are arguably more flexible. Although systemd understands runlevels with the runlevel.target, most services will tend to use multi-user.target or graphical.target. Although you can also create custom targets for various purposes.

I suspect* the runlevel targets are probably used by and intended for systemd's initscript/sysvinit compatibility layer to ease porting. I use Arch, so I can't comment specifically on this matter since most sysvinit compatibility cruft (outside init/halt/reboot/poweroff) has long been removed.

[1] https://news.ycombinator.com/item?id=13785448

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