How to backup Gentoo correctly?

[idrk]

Hi, I have some questions and doubts about how I can backup my Gentoo installation.

1. How to be able to deploy my Gentoo installation on another machine or the same machine for reinstallation
I read you can make a stage4 with some scripts like mkstage4(which is deprecated that's another story)
How do I do that? Do I make a stage4 then put in(and consistently sync it) on a external hard drive an I can use it to install Gentoo on other machines?
also I can use that if my Gentoo ever breaks after an update?

2. Is the above solution useful for the time that a single file(like a config file) is corrupted on my system and I want to recover that?
3. I also read that there's a good piece of software that's called 'Restic' which is also used for backup. Is that any useful if I wanted to use it for my current situation?
4. I asked some people and there are lots of scripts(like gentoo-install, gentoo-sync) I'm kinda confused which one to use here if I wanted to deploy on other machines quickly too, like just extract the stage4 and use the scripts to setup my gentoo installation like in the original pc
5. Is using backup system on the current machine(or even current disk) any useful? like using restic on the same drive. Is it stupid or it can get handy at times? like files missing(maybe gentoo breakage too?)
6. What things should I consider for my personal/private data? should I include my /home dir + other thingn in the backup?

[alamahant]

I use rsync to backup my entire / to a different partition before each update.
Plz see
https://wiki.archlinux.org/title/Rsync#Full_system_backup
Please add --delete also to above rsync command

[idrk]

Hi, I was recommended rsync too. But I would like to get answers to my questions because I can understand backup fully.

[figueroa]

Do a search here on the forum for stage4 and separately for backup. There are abundant electrons already been spent on those topics. I use my own stage4 script (stage4.scr) which you can also find in these forums.
_________________
Andy Figueroa
hp pavilion hpe h8-1260t/2AB5; spinning rust x3
i7-2600 @ 3.40GHz; 16 gb; Radeon HD 7570
amd64/23.0/split-usr/desktop (stable), OpenRC, -systemd -pulseaudio -uefi

[Kethreveris]

One thing I found early on when testing RSync backups and full restores, was that I needed a basic "/dev" populated. So my RSync backup script does that first;

[Hu]

The current advice in most cases is not to archive /dev at all, and instead to rely on the kernel's devtmpfs, which is automatically maintained and represents devices the kernel knows how to operate. This avoids issues if you restore the backup onto different hardware, such as creating the backup from a SATA SSD (/dev/sda) and restoring it to an NVMe (/dev/nvme0n1).

You are correct though, that a system without a valid /dev will have strange problems.

[figueroa]

With regard to /dev, I only backup/restore the the empty directory. I do the same for other system directories that don't require the content to be backed up. Since my backup process uses tar to build the compressed tarball, I use the --no-recursion switch for those directories.
_________________
Andy Figueroa
hp pavilion hpe h8-1260t/2AB5; spinning rust x3
i7-2600 @ 3.40GHz; 16 gb; Radeon HD 7570
amd64/23.0/split-usr/desktop (stable), OpenRC, -systemd -pulseaudio -uefi

[gentoo_ram]

During my backups, I use a bind-mount of the root filesystem to backup the default stage3 contents of /dev. As in "mount -o bind / /mnt/root", then backup the contents of /mnt/root/dev. In other words, reveal the contents of /dev as installed on the root filesystem before the devtmpfs is mounted. I believe the initial contents of /dev are useful to the boot process before devtmpfs is mounted.

[Hu]

For systems without an initramfs, enabling the Kconfig option DEVTMPFS_MOUNT directs the kernel to pre-mount devtmpfs, so that it is available at the very beginning of init. For systems with an initramfs, that Kconfig option is ignored, but the initramfs could provide a stub /dev (often just null, console, and tty), which is sufficient for the initramfs to explicitly mount devtmpfs. In both cases, the system can get by with a minimal and host-independent static /dev. It can rely on the kernel to provide hardware-specific device nodes.

[figueroa]

This is what I exclude when making a full system backup as a stage4 tarball, using tar's --exclude-from=FILE switch:

[AprilGrimoire]

If you are considering a backup, you can try dumping the whole disk or partitions into an image. This avoids the problem of needing to recreate filesystems, which is particularly useful in scenarios with complicated disk schemes like LVM over LUKS. Simply recreating the partitions and copying all the files might not work since UUID could be different.

[Hu]

Creating an image is wasteful, since you copy all the free space, you cannot create incremental backups, and a restore must be done to a drive with equal or greater total capacity. Additionally, if the restore drive is an SSD, you will needlessly write the old drive's free sectors to the new drive.

An image may be appropriate for forensics. For ordinary backup, I advise against it.

[figueroa]

AprilGrimoire;
It's up to the user to edit any necessary files for UUID and/or network changes. A compressed archive of the files is much more portable than a disk image owing to the reduced size of the compressed archive. My current compressed archives run < 6 GB, easily stored on-line or flash drive.
_________________
Andy Figueroa
hp pavilion hpe h8-1260t/2AB5; spinning rust x3
i7-2600 @ 3.40GHz; 16 gb; Radeon HD 7570
amd64/23.0/split-usr/desktop (stable), OpenRC, -systemd -pulseaudio -uefi

[nicop]

An often forgotten but important step before backup : do a snapshot or unmount / freeze the filesystem. Otherwise you may have corrupted files.

[figueroa]

[dmpogo]

Administering only my own machines, I do not backup system. I back up only /etc and /home. The rest I can reinstall

[simplycorbett]

Assuming you have three partitions (/ /boot /boot/efi)

Step 1(backup):

1) Boot live CD
2) Mount your installed / partition onto /mnt/gentoo
3) CD to the folder
4) Run