This is an original planning guide. It is not a vendor manual, an official standard, or legal advice. Example addresses use documentation ranges. Review every command before you paste it.
What this hour is for
free shows total, used, free, buff/cache, and available. Cache can be reclaimed. available is the number you quote when someone asks if the host is out of memory. The explainer reads numbers you type. The RSS and VSZ calculator explains two process sizes you type. Neither tool connects.
RSS is closer to the physical memory a process holds. VSZ is the address space, and it is often larger. Do not alarm on VSZ alone. Do not drop caches on a production host to make used memory look smaller.
Adding RAM is a purchase, not a command you run because one sample looked high. 192.0.2.10/24 and example.com are documentation. They stay in the note.
The change you can finish
Apply nothing while you are writing the note. When the lab window opens, it is one change on the host named in the ticket. Read the draft, then the host, then decide.
Rollback is the file, the package version, or the snapshot you saved first. You do not invent a rollback after the only copy is gone.
- Type the free numbers from a host you administer.
- Quote available, not only free.
- If a process matters, type RSS and VSZ.
- Do not drop caches.
- Do not buy RAM from one sample.
- Stop.
Mistakes that outlive the command
Linux Memory Usage Explained (free, buff/cache) goes wrong in a small set of ways. The list is here so the ticket can forbid them before the window.
- Caches dropped to pretty the number.
- VSZ treated as RAM in use.
- free ignored in favour of used.
- A host you do not administer.
- RAM ordered from one sample.
Decisions to write down
One decision for Linux Memory Usage Explained (free, buff/cache): available is the quoted number. RSS and VSZ are labeled. Caches were not dropped. The host is yours. And no hardware was ordered from this page alone.
Checks before you call it done
Confirm this before you call the change done: available is written. buff/cache is written. The hostname is written. No cache was dropped. And a process RSS is included only if you named the process. If one of those fails, stop.
# Quote available.
# Do not drop caches to pretty a graph.
# VSZ is not the RAM bill.Before you leave the host
Linux Memory Usage Explained (free, buff/cache) ends when the hostname in the prompt matches the hostname in the ticket. If it does not, you are on the wrong host. Stop. A command that succeeded on the wrong host is not progress.
The draft stays a draft until a person has read the names in it. A generator does not log into the host and does not know which disk is empty. You delete a line that names a host, a path, or an account you did not write down.
192.0.2.10/24, gateway 192.0.2.1, 198.51.100.0/24, 203.0.113.0/24, and 2001:db8::/32 are documentation. example.com is a documentation name. They belong in the note. They are not values you leave on a host because a draft included them.
prompt-for-this is a reminder that a secret is missing. It is not a password, a key, or a token you save in the ticket or in git. The real secret stays in the password store.
One change is the window. If two things move and the result is wrong, you will not know which one did it. The next change waits for its own page.
If the same step fails twice, stop for the day. The failure is the result. Adding a forum command beside a half-applied change produces a host nobody can rebuild. Restore the copy you took first.
A second person reads the hostname and the change aloud. If they cannot find them in the ticket, the note is not done. Silence is not agreement. Then leave the host alone.
This page is a planning guide. It is not a vendor manual, not an official standard, and not permission to touch a host you do not administer. You do not disable a firewall, AppArmor, or SELinux to make a check pass.
Tools for this guide
These tools run in the browser on this site. They do not log into your machines.
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