systemd-validatefs@.service - Man Page

systemd-validatefs@​.service

/usr/lib/systemd/systemd-validatefs MOUNTPOINT

systemd-validatefs@​.service is a system service template that can be instantiated for newly established mount points​. It reads file system mount constraint data from the file system, and ensures the mount runtime setup matches it​. If it doesn't the service fails, which effects an immediate reboot​.

This functionality is supposed to ensure that trusted file systems cannot be used in a different context then what they were intended for​. More specifically: in an systemd-gpt-auto-generator(8) based environment the file systems to mount are largely auto-discovered based on (unprotected) GPT partition table data​. The mount constraint information can be used to validate the GPT partition data, based on the (protected) file system contents​.

Specifically, the mount constraints are encoded in the following extended attributes on the root inode of the file systems:

1. user​.validatefs​.mount_point: this extended attribute shall contain one or more absolute, normalized paths, separated by NUL bytes​. If set and the specified file system is mounted to a location not matching any of the listed paths the validation check will fail​.
2. user​.validatefs​.gpt_label: this extended attribute may contain one or more free-form strings, separated by NUL bytes​. If set, all backing partitions of the file system are checked against this list, and if any backing partition's label is not listed, the validation will fail​. Note that there may be multiple backing partition in case of Verity setups, which combines a data and a hash partition​.
3. user​.validatefs​.gpt_type_uuid: this extended attribute may contain one or more GPT partition type UUIDs, formatted as string, separated by NUL bytes​. As above, all backing partitions of the file system are checked against this list, and if none is matching the validation will fail​.

The systemd-validatefs@​.service unit is automatically pulled into the initial transaction by systemd-gpt-auto-generator(8) for all file systems it discovers and generates mounts for​. systemd-fstab-generator(8) will do this for all mounts with the x-systemd​.validatefs mount option in /etc/fstab​.

The systemd-repart(8) tool generates these extended attributes automatically for the file systems it puts together, which may be controlled with the AddValidateFS= configuration option​.

The /usr/lib/systemd/systemd-validatefs executable may also be invoked from the command line, where it expects a path to a mount and the following options:

--root=

Takes an absolute path or the special string "auto"​. The specified path is removed as prefix from the specified mount point argument before the validation​. If set to "auto" defaults to unspecified on the host and /sysroot/ when run in initrd context, in order to validate the mount constraint data relative to the future file system root​.

Added in version 258​.

-h,  --help

Print a short help text and exit​.

--version

Print a short version string and exit​.

systemd(1), systemd-gpt-auto-generator(8), systemd-fstab-generator(8), systemd-repart(8)

repart.d(5), systemd.directives(7), systemd-gpt-auto-generator(8), systemd.index(7), systemd.mount(5).