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Merge pull request #2864 from cgwalters/prepare-root-prepare-composefs

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prepare-root: Move sysroot.tmp creation earlier
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Colin Walters 2023-05-30 09:15:40 -04:00 committed by GitHub
commit 0dd2788410
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1 changed files with 60 additions and 42 deletions
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102
src/switchroot/ostree-prepare-root.c
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@ -36,11 +36,16 @@
* hardlinked chroot() targets are maintained, this one does the equivalent * hardlinked chroot() targets are maintained, this one does the equivalent
* of chroot(). * of chroot().
* *
* # ostree-prepare-root.service
*
* If using systemd, an excellent reference is `man bootup`. This * If using systemd, an excellent reference is `man bootup`. This
* service runs Before=initrd-root-fs.target. At this point it's * service runs Before=initrd-root-fs.target. At this point it's
* assumed that the block storage and root filesystem are mounted at * assumed that the block storage and root filesystem are mounted at
* /sysroot - i.e. /sysroot points to the *physical* root before * /sysroot - i.e. /sysroot points to the *physical* root before
* this service runs. After, `/` is the deployment root. * this service runs. After, `/` is the deployment root, and /sysroot is
* the physical root.
*
* # Running as pid 1
* *
* There is also a secondary mode for this service when an initrd isn't * There is also a secondary mode for this service when an initrd isn't
* used - instead the binary must be statically linked (and the kernel * used - instead the binary must be statically linked (and the kernel
@ -78,6 +83,9 @@
SD_ID128_MAKE (71, 70, 33, 6a, 73, ba, 46, 01, ba, d3, 1a, f8, 88, aa, 0d, f7) SD_ID128_MAKE (71, 70, 33, 6a, 73, ba, 46, 01, ba, d3, 1a, f8, 88, aa, 0d, f7)
#endif #endif
// A temporary mount point
#define TMP_SYSROOT "/sysroot.tmp"
#include "ostree-mount-util.h" #include "ostree-mount-util.h"
static inline bool static inline bool
@ -202,6 +210,11 @@ main (int argc, char *argv[])
we_mounted_proc = 1; we_mounted_proc = 1;
} }
/* This is the final target where we should prepare the rootfs. The usual
* case with systemd in the initramfs is that root_mountpoint = "/sysroot".
* In the fastboot embedded case we're pid1 and will setup / ourself, and
* then root_mountpoint = "/".
* */
const char *root_mountpoint = realpath (root_arg, NULL); const char *root_mountpoint = realpath (root_arg, NULL);
if (root_mountpoint == NULL) if (root_mountpoint == NULL)
err (EXIT_FAILURE, "realpath(\"%s\")", root_arg); err (EXIT_FAILURE, "realpath(\"%s\")", root_arg);
@ -234,16 +247,23 @@ main (int argc, char *argv[])
if (mount (NULL, "/", NULL, MS_REC | MS_PRIVATE | MS_SILENT, NULL) < 0) if (mount (NULL, "/", NULL, MS_REC | MS_PRIVATE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to make \"/\" private mount"); err (EXIT_FAILURE, "failed to make \"/\" private mount");
/* Make deploy_path a bind mount, so we can move it later */ if (mkdir (TMP_SYSROOT, 0755) < 0)
if (mount (deploy_path, deploy_path, NULL, MS_BIND | MS_SILENT, NULL) < 0) err (EXIT_FAILURE, "couldn't create temporary sysroot %s", TMP_SYSROOT);
err (EXIT_FAILURE, "failed to make initial bind mount %s", deploy_path);
/* chdir to our new root. We need to do this after bind-mounting it over /* Run in the deploy_path dir so we can use relative paths below */
* itself otherwise our cwd is still on the non-bind-mounted filesystem
* below. */
if (chdir (deploy_path) < 0) if (chdir (deploy_path) < 0)
err (EXIT_FAILURE, "failed to chdir to deploy_path"); err (EXIT_FAILURE, "failed to chdir to deploy_path");
/* Currently always false */
bool using_composefs = false;
if (!using_composefs)
{
/* The deploy root starts out bind mounted to sysroot.tmp */
if (mount (deploy_path, TMP_SYSROOT, NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to make initial bind mount %s", deploy_path);
}
/* This will result in a system with /sysroot read-only. Thus, two additional /* This will result in a system with /sysroot read-only. Thus, two additional
* writable bind-mounts (for /etc and /var) are required later on. */ * writable bind-mounts (for /etc and /var) are required later on. */
if (sysroot_readonly) if (sysroot_readonly)
@ -269,7 +289,7 @@ main (int argc, char *argv[])
{ {
if (snprintf (srcpath, sizeof (srcpath), "%s/boot", root_mountpoint) < 0) if (snprintf (srcpath, sizeof (srcpath), "%s/boot", root_mountpoint) < 0)
err (EXIT_FAILURE, "failed to assemble /boot path"); err (EXIT_FAILURE, "failed to assemble /boot path");
if (mount (srcpath, "boot", NULL, MS_BIND | MS_SILENT, NULL) < 0) if (mount (srcpath, TMP_SYSROOT "/boot", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to bind mount %s to boot", srcpath); err (EXIT_FAILURE, "failed to bind mount %s to boot", srcpath);
} }
} }
@ -277,13 +297,15 @@ main (int argc, char *argv[])
/* Prepare /etc. /* Prepare /etc.
* No action required if sysroot is writable. Otherwise, a bind-mount for * No action required if sysroot is writable. Otherwise, a bind-mount for
* the deployment needs to be created and remounted as read/write. */ * the deployment needs to be created and remounted as read/write. */
if (sysroot_readonly) if (sysroot_readonly || using_composefs)
{ {
/* Bind-mount /etc (at deploy path), and remount as writable. */ /* Bind-mount /etc (at deploy path), and remount as writable. */
if (mount ("etc", "etc", NULL, MS_BIND | MS_SILENT, NULL) < 0) if (mount ("etc", TMP_SYSROOT "/etc", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to prepare /etc bind-mount at %s", srcpath); err (EXIT_FAILURE, "failed to prepare /etc bind-mount at /sysroot.tmp/etc");
if (mount ("etc", "etc", NULL, MS_BIND | MS_REMOUNT | MS_SILENT, NULL) < 0) if (mount (TMP_SYSROOT "/etc", TMP_SYSROOT "/etc", NULL, MS_BIND | MS_REMOUNT | MS_SILENT,
err (EXIT_FAILURE, "failed to make writable /etc bind-mount at %s", srcpath); NULL)
< 0)
err (EXIT_FAILURE, "failed to make writable /etc bind-mount at /sysroot.tmp/etc");
} }
/* Prepare /usr. /* Prepare /usr.
@ -291,28 +313,31 @@ main (int argc, char *argv[])
if (lstat (".usr-ovl-work", &stbuf) == 0) if (lstat (".usr-ovl-work", &stbuf) == 0)
{ {
/* Do we have a persistent overlayfs for /usr? If so, mount it now. */ /* Do we have a persistent overlayfs for /usr? If so, mount it now. */
const char usr_ovl_options[] = "lowerdir=usr,upperdir=.usr-ovl-upper,workdir=.usr-ovl-work"; const char usr_ovl_options[]
= "lowerdir=" TMP_SYSROOT "/usr,upperdir=.usr-ovl-upper,workdir=.usr-ovl-work";
/* Except overlayfs barfs if we try to mount it on a read-only /* Except overlayfs barfs if we try to mount it on a read-only
* filesystem. For this use case I think admins are going to be * filesystem. For this use case I think admins are going to be
* okay if we remount the rootfs here, rather than waiting until * okay if we remount the rootfs here, rather than waiting until
* later boot and `systemd-remount-fs.service`. * later boot and `systemd-remount-fs.service`.
*/ */
if (path_is_on_readonly_fs (".")) if (path_is_on_readonly_fs (TMP_SYSROOT))
{ {
if (mount (".", ".", NULL, MS_REMOUNT | MS_SILENT, NULL) < 0) if (mount (TMP_SYSROOT, TMP_SYSROOT, NULL, MS_REMOUNT | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to remount rootfs writable (for overlayfs)"); err (EXIT_FAILURE, "failed to remount rootfs writable (for overlayfs)");
} }
if (mount ("overlay", "usr", "overlay", MS_SILENT, usr_ovl_options) < 0) if (mount ("overlay", TMP_SYSROOT "/usr", "overlay", MS_SILENT, usr_ovl_options) < 0)
err (EXIT_FAILURE, "failed to mount /usr overlayfs"); err (EXIT_FAILURE, "failed to mount /usr overlayfs");
} }
else else if (!using_composefs)
{ {
/* Otherwise, a read-only bind mount for /usr */ /* Otherwise, a read-only bind mount for /usr. (Not needed for composefs) */
if (mount ("usr", "usr", NULL, MS_BIND | MS_SILENT, NULL) < 0) if (mount (TMP_SYSROOT "/usr", TMP_SYSROOT "/usr", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to bind mount (class:readonly) /usr"); err (EXIT_FAILURE, "failed to bind mount (class:readonly) /usr");
if (mount ("usr", "usr", NULL, MS_BIND | MS_REMOUNT | MS_RDONLY | MS_SILENT, NULL) < 0) if (mount (TMP_SYSROOT "/usr", TMP_SYSROOT "/usr", NULL,
MS_BIND | MS_REMOUNT | MS_RDONLY | MS_SILENT, NULL)
< 0)
err (EXIT_FAILURE, "failed to bind mount (class:readonly) /usr"); err (EXIT_FAILURE, "failed to bind mount (class:readonly) /usr");
} }
@ -345,7 +370,7 @@ main (int argc, char *argv[])
*/ */
if (mount_var) if (mount_var)
{ {
if (mount ("../../var", "var", NULL, MS_BIND | MS_SILENT, NULL) < 0) if (mount ("../../var", TMP_SYSROOT "/var", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to bind mount ../../var to var"); err (EXIT_FAILURE, "failed to bind mount ../../var to var");
} }
@ -357,6 +382,9 @@ main (int argc, char *argv[])
if (!running_as_pid1) if (!running_as_pid1)
touch_run_ostree (); touch_run_ostree ();
if (chdir (TMP_SYSROOT) < 0)
err (EXIT_FAILURE, "failed to chdir to " TMP_SYSROOT);
if (strcmp (root_mountpoint, "/") == 0) if (strcmp (root_mountpoint, "/") == 0)
{ {
/* pivot_root rotates two mount points around. In this instance . (the /* pivot_root rotates two mount points around. In this instance . (the
@ -371,32 +399,22 @@ main (int argc, char *argv[])
else else
{ {
/* In this instance typically we have our ready made-up up root at /* In this instance typically we have our ready made-up up root at
* /sysroot/ostree/deploy/.../ (deploy_path) and the real rootfs at * /sysroot.tmp and the physical root at /sysroot (root_mountpoint).
* /sysroot (root_mountpoint). We want to end up with our made-up root at * We want to end up with our deploy root at /sysroot/ and the physical
* /sysroot/ and the real rootfs under /sysroot/sysroot as systemd will be * root under /sysroot/sysroot as systemd will be responsible for
* responsible for moving /sysroot to /. * moving /sysroot to /.
*
* We need to do this in 3 moves to avoid trying to move /sysroot under
* itself:
*
* 1. /sysroot/ostree/deploy/... -> /sysroot.tmp
* 2. /sysroot -> /sysroot.tmp/sysroot
* 3. /sysroot.tmp -> /sysroot
*/ */
if (mkdir ("/sysroot.tmp", 0755) < 0)
err (EXIT_FAILURE, "couldn't create temporary sysroot /sysroot.tmp");
if (mount (deploy_path, "/sysroot.tmp", NULL, MS_MOVE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to MS_MOVE '%s' to '/sysroot.tmp'", deploy_path);
if (mount (root_mountpoint, "sysroot", NULL, MS_MOVE | MS_SILENT, NULL) < 0) if (mount (root_mountpoint, "sysroot", NULL, MS_MOVE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to MS_MOVE '%s' to 'sysroot'", root_mountpoint); err (EXIT_FAILURE, "failed to MS_MOVE '%s' to 'sysroot'", root_mountpoint);
if (mount (".", root_mountpoint, NULL, MS_MOVE | MS_SILENT, NULL) < 0) if (mount (".", root_mountpoint, NULL, MS_MOVE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to MS_MOVE %s to %s", deploy_path, root_mountpoint); err (EXIT_FAILURE, "failed to MS_MOVE %s to %s", ".", root_mountpoint);
if (rmdir ("/sysroot.tmp") < 0) if (chdir (root_mountpoint) < 0)
err (EXIT_FAILURE, "couldn't remove temporary sysroot /sysroot.tmp"); err (EXIT_FAILURE, "failed to chdir to %s", root_mountpoint);
if (rmdir (TMP_SYSROOT) < 0)
err (EXIT_FAILURE, "couldn't remove temporary sysroot %s", TMP_SYSROOT);
if (sysroot_readonly) if (sysroot_readonly)
{ {