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Author SHA1 Message Date
BBaoVanC 5b067faf53
Add a comment before the sudo command 2023-03-20 10:44:23 -05:00
BBaoVanC 3776ece6c7
Rename the guide 2023-03-20 10:44:22 -05:00
BBaoVanC 7f6ef16d4a
Add instructions for how to delete swapfile 2023-03-20 10:44:22 -05:00
BBaoVanC bad8875a9e
Update guide 2023-03-20 10:44:22 -05:00
BBaoVanC 3aacbe59b0
Add series and tag pages 2023-03-20 10:44:22 -05:00
BBaoVanC e7351e8aa8
Change bashsession include to an info 2023-03-20 10:44:22 -05:00
BBaoVanC 2ec910bdde
Remove tutorial heading 2023-03-20 10:44:22 -05:00
BBaoVanC e077f1348e
Add swapfile guide article drafts 2023-03-20 10:44:21 -05:00
BBaoVanC b4c695aeb4
Update bobatheme
- Remove credit.html partial
- Reorganize summary template files
- Fix margin around post-title
- Remove series position indicator
- :3
2023-03-18 21:39:27 -05:00
BBaoVanC cdfcf3c372
Add procursus.social <link> 2023-02-24 22:47:43 -06:00
BBaoVanC 6d7dfa6c5d
Fix <code> font size in comments 2023-02-22 16:41:16 -06:00
9 changed files with 348 additions and 3 deletions

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@ -46,7 +46,8 @@ a.isso-author:hover,
border: none;
padding: 2px 4px;
border-radius: 5px;
font-size: 100%;
/* thanks isso.css for setting this to 85% for whatever reason */
font-size: 0.75em;
}
.isso-input-wrapper input,

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@ -0,0 +1,53 @@
---
title: Swapfile guide explained
date: 2023-01-23T20:26:18-06:00
lastmod: 2023-01-23T20:26:18-06:00
toc: true
comments: true
draft: true
authors:
- bbaovanc
categories:
- linux
tags:
- linux-swap
- swapfile
series:
- swapfile-guide
# this will be shown for the article in list pages and in the page metadata
# it can be either an image or video (this might change in the future, however)
resources:
- name: feature
src: something.webp
title: Some image (image format can be anything; webp is just an example)
---
This page is about something. All the content before the "more" HTML comment
below will become the summary, which will be used in list pages and in the meta
tags on the article.
Or, if you don't want your description to be at the top of the article, you can
set your own `description` in the front matter and it will override this. See
the [Content Summaries](https://gohugo.io/content-management/summaries/) page on
the Hugo docs for more information.
<!--more-->
## Allocating the file
- use `dd` instead of `fallocate`
- https://man7.org/linux/man-pages/man8/swapon.8.html#NOTES
- https://man.archlinux.org/man/core/util-linux/swapon.8.en#Files_with_holes
## Options field
- https://unix.stackexchange.com/a/365961/525130
- https://unix.stackexchange.com/a/365954/525130
- https://github.com/util-linux/util-linux/blob/2ea397239683270a0fc8cd3b72ed5457f52dbda8/sys-utils/swapon.c#L699

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@ -0,0 +1,253 @@
---
title: How to create (or remove) a swapfile on Linux
date: 2023-01-23T20:26:18-06:00
lastmod: 2023-01-23T20:26:18-06:00
toc: true
comments: true
draft: true
authors:
- bbaovanc
categories:
- guides
- linux
- tips-and-tricks
tags:
- linux-swap
- swapfile
series:
- swapfile-guide
# this will be shown for the article in list pages and in the page metadata
# it can be either an image or video (this might change in the future, however)
resources:
- name: feature
src: something.webp
title: Some image (image format can be anything; webp is just an example)
---
This is a step-by-step tutorial on how to create or remove a swapfile on a Linux
machine. Also included is the correct `fstab` entry (most articles get this
"wrong", though it doesn't really make a difference) and reasons to use
swap(file) in the first place.
<!--more-->
## Should you use swap?
A common misconception is that adding swap to your system can reduce
performance. In reality, even if you aren't running out of RAM, it can still be
beneficial to add swap.
See these points according to [an article by Hayden James][always-add-swap]:
> - Even if there is still available RAM, the Linux Kernel will **move memory
> pages that are hardly ever used** into swap space.
>
> - Its better to swap out memory pages that have been inactive for a while,
> **keeping often-used data in cache**, and this should happen when the server
> is most idle, which is the aim of the Kernel.
>
> - Avoid setting your swap space too large if it will result in prolonging
> performance issues, outages, or your response time (without proper
> monitoring/alerts).
[always-add-swap]: https://haydenjames.io/linux-performance-almost-always-add-swap-space/
### Should you use a swapfile?
Swap partitions should be preferred because swapfiles tend to be slower and more
complex, especially if hibernating. A swapfile might be preferred due to its
flexibility (easy to resize), but if you use [LVM][lvm-archwiki] then you can
easily resize the swap partition anyways.
[lvm-archwiki]: https://wiki.archlinux.org/title/LVM
## Tutorial
{{< include path="include/bashsession.md" markdown=true >}}
### Step 1: Create the file
The first step is to allocate the file.
```bashsession
# dd if=/dev/zero of=/swapfile bs=1M count=[size in MiB] status=progress
```
Replace `[size in MiB]` with the size of your swapfile in Mebibytes (MiB). You
can use [this online converter](https://www.convertunits.com/from/GiB/to/MiB) to
convert from Gibibytes (GiB, often confused with Gigabytes, but that's a
misconception for another time) to MiB, which you can put in the command.
Or you can look at this table for common sizes:
{{< table >}}
| GiB | MiB |
|-----|-------------|
| 1 | count=1024 |
| 2 | count=2048 |
| 3 | count=3072 |
| 4 | count=4096 |
| 8 | count=8192 |
| 16 | count=16384 |
{{< /table >}}
If you aren't sure how big your swapfile should be, take a look at [Table 15.1
on this Red Hat documentation page][redhat-swap-table]. Remember that if your
first swapfile isn't large enough, you can create another one.
[redhat-swap-table]: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/ch-swapspace#tb-recommended-system-swap-space
On my computer I have 32 GiB of RAM and a 16 GiB swap partition, rather than
swapfile, because I can flexibly expand the swap partition using
[LVM][lvm-archwiki].
{{< aside example >}}
To create a swapfile 4 GiB in size, you would run:
```bashsession
# dd if=/dev/zero of=/swapfile bs=1M count=4096 status=progress
4096+0 records in
4096+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 0.960183 s, 4.5 GB/s
```
{{< /aside >}}
### Step 2: Change swapfile permissions
The swapfile should only be readable by the system (`root` user). Run this
command to change it:
```bashsession
# chmod 600 /swapfile
```
### Step 3: Format the swapfile
Use the `mkswap` command to format the file to be used as swap (basically just
add a header to identify it):
```bashsession
# mkswap /swapfile
Setting up swapspace version 1, size = 4 GiB (4294963200 bytes)
no label, UUID=a0b87eca-b951-4344-be2d-020d77cdef48
```
### Step 4: Create an entry in `/etc/fstab`
An entry needs to be added to `/etc/fstab` for the swapfile to be enabled during
bootup. Open `/etc/fstab` in a text editor, and add this line to the end (add
spaces to line up with other entries if you want, whitespace is ignored):
```text
/swapfile none swap sw 0 0
```
{{< aside note >}}
Above, I have filled the "options" field with `sw`. This is actually a result of
[cargo culting](https://en.wiktionary.org/wiki/cargo_culting). On Linux, the
`sw` option (and the [options specified by the commonly used
`defaults`][fstab-defaults-man]) [isn't valid for `swapon` and is
ignored][swapon-options-source]. However, the field does need to be filled out
with something, so feel free to put something funny (do let me know in the
comments if this somehow breaks something though).
[fstab-defaults-man]: https://man.archlinux.org/man/fstab.5#The_fourth_field_(%3Ci%3Efs_mntops%3C/i%3E).
[swapon-options-source]: https://github.com/util-linux/util-linux/blob/2ea397239683270a0fc8cd3b72ed5457f52dbda8/sys-utils/swapon.c#L699
If you're curious, this is my `fstab` entry (`UUID` is because I use a swap
partition, rather than swapfile):
```text
# /dev/mapper/bobavg0-swap
UUID=4f7c3ae8-839b-4474-b8a5-96bd78db06f8 none swap bobaswap 0 0
```
{{< /aside >}}
### Step 5: Enable the swapfile
Adding the `fstab` entry won't enable the swapfile until a reboot. To enable it
now, use the `swapon` command.
```bashsession
# swapon /swapfile
```
### Finally: check the swap status
Use `swapon` and `free` to verify that your new swapfile has been added:
```bashsession
$ swapon --show
NAME TYPE SIZE USED PRIO
/swapfile file 4G 0B -2
$ free -h
total used free shared buff/cache available
Mem: 31Gi 3.6Gi 20Gi 233Mi 6.9Gi 26Gi
Swap: 4.0Gi 0B 4.0Gi
```
{{< aside note >}}
If you get an error saying that the `swapon` command was not found, try running
it as `root` (using `sudo`). On Debian-based distributions the `swapon` command
is not available to regular users.
```bashsession
$ swapon --show
bash: swapon: command not found
# swapon --show
NAME TYPE SIZE USED PRIO
/swapfile file 4G 0B -2
```
{{< /aside >}}
## Removing a swapfile
{{< aside warning >}}
Be careful that the swapfile isn't being highly used because once you run
`swapoff`, it will dump the entire contents back into RAM and may cause you to
run out of memory.
{{< /aside >}}
### Step 1: Disable/unload the swapfile
```bashsession
$ swapon --show
NAME TYPE SIZE USED PRIO
/swapfile file 4G 0B -2
$ # the path to the swapfile I want to remove is `/swapfile`
# swapoff /swapfile
```
### Step 2: Remove the entry from `fstab`
Open `/etc/fstab` in a text editor and find the line matching the swapfile you
want to remove, and delete it. For example:
```text
/swapfile none swap sw 0 0
```
### Step 3: Delete the actual file
```bashsession
# rm /swapfile
```

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@ -0,0 +1,10 @@
---
title: Swapfile Guide
---
A tutorial on how to set up a swapfile on Linux, but with some more depth than
just a step-by-step.
<!--more-->

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@ -0,0 +1,13 @@
---
title: Swap (Linux)
---
Swap space is storage on your drive that can be used as virtual memory when the
system is running low on physical memory (RAM). It is also used when hibernating
(suspend to disk).
More information: https://haydenjames.io/linux-performance-almost-always-add-swap-space/
<!--more-->

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@ -0,0 +1,11 @@
---
title: swapfile
---
A swapfile is a file that gives your system more [swap]({{< relref
"../linux-swap" >}}) space, which is used when the system is running low on RAM,
or when hibernating.
<!--more-->

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@ -1,4 +1,4 @@
{{< aside tip >}}
{{< aside info >}}
Commands in this article are prefixed them with a prompt symbol (either `$` or
`#`) which is not part of the command. Lines with no prompt symbol are output
@ -17,6 +17,8 @@ $ # regular users aren't allowed to view /var/lib/docker, we need root
builder containerd image overlay2 runtimes tmp volumes
buildkit containers network plugins swarm trust
$ # we can do the same thing using sudo
$ sudo ls /var/lib/docker
[sudo] password for bbaovanc:
builder containerd image overlay2 runtimes tmp volumes

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@ -2,3 +2,5 @@
<script defer data-domain="bbaovanc.com" src="https://plausible.bbaovanc.com/js/bobalytics.outbound-links.js"></script>
<script>window.plausible = window.plausible || function() { (window.plausible.q = window.plausible.q || []).push(arguments) }</script>
{{ end }}
<link rel="me" href="https://procursus.social/@bbaovanc" />

@ -1 +1 @@
Subproject commit 1caa7acdc9c0bf00ea38524538d295a6c179ae6d
Subproject commit d34b2a56d7e50681c5b128be771e05069a42313b