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docs: document the three new env vars for tweaking GPT dissection/validation

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Lennart Poettering 2021-09-10 11:01:09 +02:00
parent 77617993ee
commit 54dcf847b1
1 changed files with 42 additions and 14 deletions
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docs/ENVIRONMENT.md
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@ -23,17 +23,17 @@ All tools:
* `$SYSTEMD_OFFLINE=[0|1]` — if set to `1`, then `systemctl` will refrain from * `$SYSTEMD_OFFLINE=[0|1]` — if set to `1`, then `systemctl` will refrain from
talking to PID 1; this has the same effect as the historical detection of talking to PID 1; this has the same effect as the historical detection of
`chroot()`. Setting this variable to `0` instead has a similar effect as `chroot()`. Setting this variable to `0` instead has a similar effect as
`SYSTEMD_IGNORE_CHROOT=1`; i.e. tools will try to communicate with PID 1 even `$SYSTEMD_IGNORE_CHROOT=1`; i.e. tools will try to communicate with PID 1
if a `chroot()` environment is detected. You almost certainly want to set even if a `chroot()` environment is detected. You almost certainly want to
this to `1` if you maintain a package build system or similar and are trying set this to `1` if you maintain a package build system or similar and are
to use a modern container system and not plain `chroot()`. trying to use a modern container system and not plain `chroot()`.
* `$SYSTEMD_IGNORE_CHROOT=1` — if set, don't check whether being invoked in a * `$SYSTEMD_IGNORE_CHROOT=1` — if set, don't check whether being invoked in a
`chroot()` environment. This is particularly relevant for systemctl, as it `chroot()` environment. This is particularly relevant for systemctl, as it
will not alter its behaviour for `chroot()` environments if set. Normally it will not alter its behaviour for `chroot()` environments if set. Normally it
refrains from talking to PID 1 in such a case; turning most operations such refrains from talking to PID 1 in such a case; turning most operations such
as `start` into no-ops. If that's what's explicitly desired, you might as `start` into no-ops. If that's what's explicitly desired, you might
consider setting `SYSTEMD_OFFLINE=1`. consider setting `$SYSTEMD_OFFLINE=1`.
* `$SD_EVENT_PROFILE_DELAYS=1` — if set, the sd-event event loop implementation * `$SD_EVENT_PROFILE_DELAYS=1` — if set, the sd-event event loop implementation
will print latency information at runtime. will print latency information at runtime.
@ -96,7 +96,7 @@ All tools:
* `$SYSTEMD_RDRAND=0` — if set, the RDRAND instruction will never be used, * `$SYSTEMD_RDRAND=0` — if set, the RDRAND instruction will never be used,
even if the CPU supports it. even if the CPU supports it.
* `$SYSTEMD_SECCOMP=0` – if set, seccomp filters will not be enforced, even if * `$SYSTEMD_SECCOMP=0` — if set, seccomp filters will not be enforced, even if
support for it is compiled in and available in the kernel. support for it is compiled in and available in the kernel.
* `$SYSTEMD_LOG_SECCOMP=1` — if set, system calls blocked by seccomp filtering, * `$SYSTEMD_LOG_SECCOMP=1` — if set, system calls blocked by seccomp filtering,
@ -189,7 +189,7 @@ All tools:
`systemd-udevd`: `systemd-udevd`:
* `$NET_NAMING_SCHEME=` – if set, takes a network naming scheme (i.e. one of * `$NET_NAMING_SCHEME=` — if set, takes a network naming scheme (i.e. one of
"v238", "v239", "v240"…, or the special value "latest") as parameter. If "v238", "v239", "v240"…, or the special value "latest") as parameter. If
specified udev's `net_id` builtin will follow the specified naming scheme specified udev's `net_id` builtin will follow the specified naming scheme
when determining stable network interface names. This may be used to revert when determining stable network interface names. This may be used to revert
@ -267,13 +267,13 @@ All tools:
`systemd-firstboot` and `localectl`: `systemd-firstboot` and `localectl`:
* `SYSTEMD_LIST_NON_UTF8_LOCALES=1` – if set, non-UTF-8 locales are listed among * `$SYSTEMD_LIST_NON_UTF8_LOCALES=1` — if set, non-UTF-8 locales are listed among
the installed ones. By default non-UTF-8 locales are suppressed from the the installed ones. By default non-UTF-8 locales are suppressed from the
selection, since we are living in the 21st century. selection, since we are living in the 21st century.
`systemd-sysext`: `systemd-sysext`:
* `SYSTEMD_SYSEXT_HIERARCHIES` – this variable may be used to override which * `$SYSTEMD_SYSEXT_HIERARCHIES` — this variable may be used to override which
hierarchies are managed by `systemd-sysext`. By default only `/usr/` and hierarchies are managed by `systemd-sysext`. By default only `/usr/` and
`/opt/` are managed, and directories may be added or removed to that list by `/opt/` are managed, and directories may be added or removed to that list by
setting this environment variable to a colon-separated list of absolute setting this environment variable to a colon-separated list of absolute
@ -284,7 +284,7 @@ All tools:
`systemd-tmpfiles`: `systemd-tmpfiles`:
* `SYSTEMD_TMPFILES_FORCE_SUBVOL` — if unset, `v`/`q`/`Q` lines will create * `$SYSTEMD_TMPFILES_FORCE_SUBVOL` — if unset, `v`/`q`/`Q` lines will create
subvolumes only if the OS itself is installed into a subvolume. If set to `1` subvolumes only if the OS itself is installed into a subvolume. If set to `1`
(or another value interpreted as true), these lines will always create (or another value interpreted as true), these lines will always create
subvolumes if the backing filesystem supports them. If set to `0`, these subvolumes if the backing filesystem supports them. If set to `0`, these
@ -318,21 +318,49 @@ fuzzers:
Note that is may be also useful to set `$SYSTEMD_LOG_LEVEL`, since all logging Note that is may be also useful to set `$SYSTEMD_LOG_LEVEL`, since all logging
is suppressed by default. is suppressed by default.
systemd-importd: `systemd-importd`:
* `SYSTEMD_IMPORT_BTRFS_SUBVOL` – takes a boolean, which controls whether to * `$SYSTEMD_IMPORT_BTRFS_SUBVOL` — takes a boolean, which controls whether to
prefer creating btrfs subvolumes over plain directories for machine prefer creating btrfs subvolumes over plain directories for machine
images. Has no effect on non-btrfs file systems where subvolumes are not images. Has no effect on non-btrfs file systems where subvolumes are not
available anyway. If not set, defaults to true. available anyway. If not set, defaults to true.
* `SYSTEMD_IMPORT_BTRFS_QUOTA` – takes a boolean, which controls whether to set * `$SYSTEMD_IMPORT_BTRFS_QUOTA` — takes a boolean, which controls whether to set
up quota automatically for created btrfs subvolumes for machine images. If up quota automatically for created btrfs subvolumes for machine images. If
not set, defaults to true. Has no effect if machines are placed in regular not set, defaults to true. Has no effect if machines are placed in regular
directories, because btrfs subvolumes are not supported or disabled. If directories, because btrfs subvolumes are not supported or disabled. If
enabled, the quota group of the subvolume is automatically added to a enabled, the quota group of the subvolume is automatically added to a
combined quota group for all such machine subvolumes. combined quota group for all such machine subvolumes.
* `SYSTEMD_IMPORT_SYNC` – takes a boolean, which controls whether to * `$SYSTEMD_IMPORT_SYNC` — takes a boolean, which controls whether to
synchronize images to disk after installing them, before completing the synchronize images to disk after installing them, before completing the
operation. If not set, defaults to true. If disabled installation of images operation. If not set, defaults to true. If disabled installation of images
will be quicker, but not as safe. will be quicker, but not as safe.
`systemd-dissect`, `systemd-nspawn` and all other tools that may operate on
disk images with `--image=` or similar:
* `$SYSTEMD_DISSECT_VERITY_SIDECAR` — takes a boolean, which controls whether to
load "sidecar" Verity metadata files. If enabled (which is the default),
whenever a disk image is used, a set of files with the `.roothash`,
`.usrhash`, `.roothash.p7s`, `.usrhash.p7s`, `.verity` suffixes are searched
adjacent to disk image file, containing the Verity root hashes, their
signatures or the Verity data itself. If disabled this automatic discovery of
Verity metadata files is turned off.
* `$SYSTEMD_DISSECT_VERITY_EMBEDDED` — takes a boolean, which controls whether
to load the embedded Verity signature data. If enabled (which is the
default), Verity root hash information and a suitable signature is
automatically acquired from a signature partition, following the
[Discoverable Partitions
Specification](https://systemd.io/DISCOVERABLE_PARTITIONS). If disabled any
such partition is ignored. Note that this only disables discovery of the root
hash and its signature, the Verity data partition itself is still searched in
the GPT image.
* `$SYSTEMD_DISSECT_VERITY_SIGNATURE` — takes a boolean, which controls whether
to validate the signature of the Verity root hash if available. If enabled
(which is the default), the signature of suitable disk images is validated
against any of the certificates in `/etc/verity.d/*.crt` (and similar
directores in `/usr/lib/`, `/run`, …) or passed to the kernel for validation
against its built-in certificates.