Difference between revisions of "Change root"
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[https://en.wikipedia.org/wiki/Chroot Chroot] is an operation that changes the apparent root directory for the current running process and their children. A program that is run in such a modified environment cannot access files and commands outside that environmental directory tree. This modified environment is called a chroot jail. | [https://en.wikipedia.org/wiki/Chroot Chroot] is an operation that changes the apparent root directory for the current running process and their children. A program that is run in such a modified environment cannot access files and commands outside that environmental directory tree. This modified environment is called a chroot jail. | ||
| − | = | + | = Using nixos-enter = |
| − | nixos-enter allows to access a | + | nixos-enter allows to access a NixOS installation from a NixOS rescue system. |
| − | + | The nixos-enter program is part of NixOS. Before it runs provides a shell, the script mounts api filesystems like /proc and setups the profile and /etc of the target system. To use it, setup <code>/mnt</code> as described in the [https://nixos.org/nixos/manual/#sec-installation installation manual]. | |
| − | |||
| − | The nixos-enter program is part of | ||
Then run <code>nixos-enter</code>: | Then run <code>nixos-enter</code>: | ||
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$ nixos-enter | $ nixos-enter | ||
</syntaxHighlight> | </syntaxHighlight> | ||
| + | |||
| + | = Manual chroot = | ||
| + | |||
| + | If a NixOS rescue system is not available, the chroot can be done manually from another Linux distribution. | ||
| + | |||
| + | Mount the file system containing the NixOS to chroot into at <code>/mnt</code>, using e.g.: | ||
| + | |||
| + | <syntaxHighlight lang=bash> | ||
| + | mount /dev/relevantPartitionNameHere /mnt | ||
| + | </syntaxHighlight>. | ||
| + | |||
| + | Mount the host system's Linux run-time api file systems inside the mount, then populate <code>/run</code> using the <code>activate</code> script and chroot inside, starting a bash shell (adapted from [https://nixos.org/nix-dev/2014-December/015253.html here]; you may copy all these lines into your terminal as one block to run them): | ||
| + | |||
| + | <syntaxHighlight lang=bash> | ||
| + | mount -o bind /dev /mnt/dev | ||
| + | mount -o bind /proc /mnt/proc | ||
| + | mount -o bind /sys /mnt/sys | ||
| + | chroot /mnt /nix/var/nix/profiles/system/activate | ||
| + | chroot /mnt /run/current-system/sw/bin/bash | ||
| + | </syntaxHighlight> | ||
| + | |||
| + | You should now be in your NixOS system, and should be able to adjust it by e.g. editing <code>/etc/nixos/configuration.nix</code> and running <code>nixos-rebuild switch</code> as usual. Remember that you may have to establish Internet access the chroot for some commands. | ||
Revision as of 00:36, 5 December 2019
Chroot is an operation that changes the apparent root directory for the current running process and their children. A program that is run in such a modified environment cannot access files and commands outside that environmental directory tree. This modified environment is called a chroot jail.
Using nixos-enter
nixos-enter allows to access a NixOS installation from a NixOS rescue system.
The nixos-enter program is part of NixOS. Before it runs provides a shell, the script mounts api filesystems like /proc and setups the profile and /etc of the target system. To use it, setup /mnt as described in the installation manual.
Then run nixos-enter:
$ nixos-enter
Manual chroot
If a NixOS rescue system is not available, the chroot can be done manually from another Linux distribution.
Mount the file system containing the NixOS to chroot into at /mnt, using e.g.:
mount /dev/relevantPartitionNameHere /mnt
.
Mount the host system's Linux run-time api file systems inside the mount, then populate /run using the activate script and chroot inside, starting a bash shell (adapted from here; you may copy all these lines into your terminal as one block to run them):
mount -o bind /dev /mnt/dev
mount -o bind /proc /mnt/proc
mount -o bind /sys /mnt/sys
chroot /mnt /nix/var/nix/profiles/system/activate
chroot /mnt /run/current-system/sw/bin/bash
You should now be in your NixOS system, and should be able to adjust it by e.g. editing /etc/nixos/configuration.nix and running nixos-rebuild switch as usual. Remember that you may have to establish Internet access the chroot for some commands.