Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
Hi Rob, On Thu, 2018-02-01 at 17:34 -0600, Rob Landley wrote: > > On 02/01/2018 04:41 PM, Taras Kondratiuk wrote: > > Quoting Mimi Zohar (2018-02-01 13:51:52) > >> On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: > >>> On 02/01/2018 09:55 AM, Mimi Zohar wrote: > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > >> With your patch and specifying "root=tmpfs", dracut is complaining: > >> > >> dracut: FATAL: Don't know how to handle 'root=tmpfs' > >> dracut: refusing to continue > > > > [googles]... I do not understand why this package exists. > > > > If you're switching to another root filesystem, using a tool that > > wikipedia[citation needed] says has no purpose but to switch to another > > root filesystem, (so let's reproduce the kernel infrastructure in > > userspace while leaving it the kernel too)... why do you need initramfs > > to be tmpfs? You're using it for half a second, then discarding it, > > what's the point of it being tmpfs? > > Unlike the kernel image which is signed by the distros, the initramfs > doesn't come signed, because it is built on the target system. Even > if the initramfs did come signed, it is beneficial to measure and > appraise the individual files in the initramfs. > >>> > >>> You can still shoot yourself in the foot with tmpfs. People mount a /run > >>> and a /tmp and then as a normal user you can go > >>> https://twitter.com/landley/status/959103235305951233 and maybe the > >>> default should be a little more clever there... > >>> > >>> I'll throw it on the todo heap. :) > >>> > > Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > > is configured in, even when you're then going to overmount it with > > something else like you're doing, let's just _remove_ the test. If it > > can be tmpfs, have it be tmpfs. > > Very much appreciated! > >>> > >>> Not yet tested, but something like the attached? (Sorry for the > >>> half-finished doc changes in there, I'm at work and have a 5 minute > >>> break. I can test properly this evening if you don't get to it...) > >> > >> Yes, rootfs is being mounted as tmpfs. > > > > I don't think you can unconditionally replace ramfs with initramfs by > > default. Their behavior is different in some cases (e.g. pivot_root vs > > switch_root) > > Both are switch_root, you can't pivot_root off of either one. (Yes, I > hit that bug and reported it, and they fixed it, back in the day... > http://lists.busybox.net/pipermail/busybox/2006-March/053529.html ) > > > and it can break many systems that expect ramfs by default. > > The use case I told Mimi about off-list (since they stopped cc:ing the > list in one of their replies but the conversation continued) was the guy > who was extracting an initramfs bigger than 50% of system memory, which > worked with initramfs but failed with initmpfs. A quick google didn't > find the original message but it resulted in this blog entry from the > affected party: > > http://www.lightofdawn.org/blog/?viewDetailed=00128 > > I.E. yeah, I know, I need to redo these patches tonight. I'd really like to be able to have rootfs be a tmpfs filesystem. Any time estimate on this patch? thanks! Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
Hi Rob, On Thu, 2018-02-01 at 17:34 -0600, Rob Landley wrote: > > On 02/01/2018 04:41 PM, Taras Kondratiuk wrote: > > Quoting Mimi Zohar (2018-02-01 13:51:52) > >> On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: > >>> On 02/01/2018 09:55 AM, Mimi Zohar wrote: > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > >> With your patch and specifying "root=tmpfs", dracut is complaining: > >> > >> dracut: FATAL: Don't know how to handle 'root=tmpfs' > >> dracut: refusing to continue > > > > [googles]... I do not understand why this package exists. > > > > If you're switching to another root filesystem, using a tool that > > wikipedia[citation needed] says has no purpose but to switch to another > > root filesystem, (so let's reproduce the kernel infrastructure in > > userspace while leaving it the kernel too)... why do you need initramfs > > to be tmpfs? You're using it for half a second, then discarding it, > > what's the point of it being tmpfs? > > Unlike the kernel image which is signed by the distros, the initramfs > doesn't come signed, because it is built on the target system. Even > if the initramfs did come signed, it is beneficial to measure and > appraise the individual files in the initramfs. > >>> > >>> You can still shoot yourself in the foot with tmpfs. People mount a /run > >>> and a /tmp and then as a normal user you can go > >>> https://twitter.com/landley/status/959103235305951233 and maybe the > >>> default should be a little more clever there... > >>> > >>> I'll throw it on the todo heap. :) > >>> > > Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > > is configured in, even when you're then going to overmount it with > > something else like you're doing, let's just _remove_ the test. If it > > can be tmpfs, have it be tmpfs. > > Very much appreciated! > >>> > >>> Not yet tested, but something like the attached? (Sorry for the > >>> half-finished doc changes in there, I'm at work and have a 5 minute > >>> break. I can test properly this evening if you don't get to it...) > >> > >> Yes, rootfs is being mounted as tmpfs. > > > > I don't think you can unconditionally replace ramfs with initramfs by > > default. Their behavior is different in some cases (e.g. pivot_root vs > > switch_root) > > Both are switch_root, you can't pivot_root off of either one. (Yes, I > hit that bug and reported it, and they fixed it, back in the day... > http://lists.busybox.net/pipermail/busybox/2006-March/053529.html ) > > > and it can break many systems that expect ramfs by default. > > The use case I told Mimi about off-list (since they stopped cc:ing the > list in one of their replies but the conversation continued) was the guy > who was extracting an initramfs bigger than 50% of system memory, which > worked with initramfs but failed with initmpfs. A quick google didn't > find the original message but it resulted in this blog entry from the > affected party: > > http://www.lightofdawn.org/blog/?viewDetailed=00128 > > I.E. yeah, I know, I need to redo these patches tonight. I'd really like to be able to have rootfs be a tmpfs filesystem. Any time estimate on this patch? thanks! Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 02/01/2018 04:41 PM, Taras Kondratiuk wrote: > Quoting Mimi Zohar (2018-02-01 13:51:52) >> On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: >>> On 02/01/2018 09:55 AM, Mimi Zohar wrote: On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: >> With your patch and specifying "root=tmpfs", dracut is complaining: >> >> dracut: FATAL: Don't know how to handle 'root=tmpfs' >> dracut: refusing to continue > > [googles]... I do not understand why this package exists. > > If you're switching to another root filesystem, using a tool that > wikipedia[citation needed] says has no purpose but to switch to another > root filesystem, (so let's reproduce the kernel infrastructure in > userspace while leaving it the kernel too)... why do you need initramfs > to be tmpfs? You're using it for half a second, then discarding it, > what's the point of it being tmpfs? Unlike the kernel image which is signed by the distros, the initramfs doesn't come signed, because it is built on the target system. Even if the initramfs did come signed, it is beneficial to measure and appraise the individual files in the initramfs. >>> >>> You can still shoot yourself in the foot with tmpfs. People mount a /run >>> and a /tmp and then as a normal user you can go >>> https://twitter.com/landley/status/959103235305951233 and maybe the >>> default should be a little more clever there... >>> >>> I'll throw it on the todo heap. :) >>> > Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > is configured in, even when you're then going to overmount it with > something else like you're doing, let's just _remove_ the test. If it > can be tmpfs, have it be tmpfs. Very much appreciated! >>> >>> Not yet tested, but something like the attached? (Sorry for the >>> half-finished doc changes in there, I'm at work and have a 5 minute >>> break. I can test properly this evening if you don't get to it...) >> >> Yes, rootfs is being mounted as tmpfs. > > I don't think you can unconditionally replace ramfs with initramfs by > default. Their behavior is different in some cases (e.g. pivot_root vs > switch_root) Both are switch_root, you can't pivot_root off of either one. (Yes, I hit that bug and reported it, and they fixed it, back in the day... http://lists.busybox.net/pipermail/busybox/2006-March/053529.html ) > and it can break many systems that expect ramfs by default. The use case I told Mimi about off-list (since they stopped cc:ing the list in one of their replies but the conversation continued) was the guy who was extracting an initramfs bigger than 50% of system memory, which worked with initramfs but failed with initmpfs. A quick google didn't find the original message but it resulted in this blog entry from the affected party: http://www.lightofdawn.org/blog/?viewDetailed=00128 I.E. yeah, I know, I need to redo these patches tonight. Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 02/01/2018 04:41 PM, Taras Kondratiuk wrote: > Quoting Mimi Zohar (2018-02-01 13:51:52) >> On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: >>> On 02/01/2018 09:55 AM, Mimi Zohar wrote: On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: >> With your patch and specifying "root=tmpfs", dracut is complaining: >> >> dracut: FATAL: Don't know how to handle 'root=tmpfs' >> dracut: refusing to continue > > [googles]... I do not understand why this package exists. > > If you're switching to another root filesystem, using a tool that > wikipedia[citation needed] says has no purpose but to switch to another > root filesystem, (so let's reproduce the kernel infrastructure in > userspace while leaving it the kernel too)... why do you need initramfs > to be tmpfs? You're using it for half a second, then discarding it, > what's the point of it being tmpfs? Unlike the kernel image which is signed by the distros, the initramfs doesn't come signed, because it is built on the target system. Even if the initramfs did come signed, it is beneficial to measure and appraise the individual files in the initramfs. >>> >>> You can still shoot yourself in the foot with tmpfs. People mount a /run >>> and a /tmp and then as a normal user you can go >>> https://twitter.com/landley/status/959103235305951233 and maybe the >>> default should be a little more clever there... >>> >>> I'll throw it on the todo heap. :) >>> > Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > is configured in, even when you're then going to overmount it with > something else like you're doing, let's just _remove_ the test. If it > can be tmpfs, have it be tmpfs. Very much appreciated! >>> >>> Not yet tested, but something like the attached? (Sorry for the >>> half-finished doc changes in there, I'm at work and have a 5 minute >>> break. I can test properly this evening if you don't get to it...) >> >> Yes, rootfs is being mounted as tmpfs. > > I don't think you can unconditionally replace ramfs with initramfs by > default. Their behavior is different in some cases (e.g. pivot_root vs > switch_root) Both are switch_root, you can't pivot_root off of either one. (Yes, I hit that bug and reported it, and they fixed it, back in the day... http://lists.busybox.net/pipermail/busybox/2006-March/053529.html ) > and it can break many systems that expect ramfs by default. The use case I told Mimi about off-list (since they stopped cc:ing the list in one of their replies but the conversation continued) was the guy who was extracting an initramfs bigger than 50% of system memory, which worked with initramfs but failed with initmpfs. A quick google didn't find the original message but it resulted in this blog entry from the affected party: http://www.lightofdawn.org/blog/?viewDetailed=00128 I.E. yeah, I know, I need to redo these patches tonight. Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/31/2018 10:22 PM, Mimi Zohar wrote: > On Wed, 2018-01-31 at 21:03 -0500, Arvind Sankar wrote: >> On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: >>> On 01/31/2018 04:07 PM, Mimi Zohar wrote: On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I configured in tmpfs and am using rootfs but I want that >>> rootfs > to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > it?) I must be missing something. Which systems don't specify "root=" on the boot command line. >>> >>> Any system using initrd or initramfs? >>> >> >> Don't a lot of initramfs setups use root= to tell the initramfs which >> actual root file system to switch to after early boot? > > With your patch and specifying "root=tmpfs", dracut is complaining: > > dracut: FATAL: Don't know how to handle 'root=tmpfs' > dracut: refusing to continue "The kernel can't break this buggy userspace package." "The kernel must give access to a new feature to this buggy userspace package". I think kernel policy asks you to pick one, but I could be wrong... Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/31/2018 10:22 PM, Mimi Zohar wrote: > On Wed, 2018-01-31 at 21:03 -0500, Arvind Sankar wrote: >> On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: >>> On 01/31/2018 04:07 PM, Mimi Zohar wrote: On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I configured in tmpfs and am using rootfs but I want that >>> rootfs > to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > it?) I must be missing something. Which systems don't specify "root=" on the boot command line. >>> >>> Any system using initrd or initramfs? >>> >> >> Don't a lot of initramfs setups use root= to tell the initramfs which >> actual root file system to switch to after early boot? > > With your patch and specifying "root=tmpfs", dracut is complaining: > > dracut: FATAL: Don't know how to handle 'root=tmpfs' > dracut: refusing to continue "The kernel can't break this buggy userspace package." "The kernel must give access to a new feature to this buggy userspace package". I think kernel policy asks you to pick one, but I could be wrong... Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
Quoting Mimi Zohar (2018-02-01 13:51:52) > On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: > > On 02/01/2018 09:55 AM, Mimi Zohar wrote: > > > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > > > > >>> With your patch and specifying "root=tmpfs", dracut is complaining: > > >>> > > >>> dracut: FATAL: Don't know how to handle 'root=tmpfs' > > >>> dracut: refusing to continue > > >> > > >> [googles]... I do not understand why this package exists. > > >> > > >> If you're switching to another root filesystem, using a tool that > > >> wikipedia[citation needed] says has no purpose but to switch to another > > >> root filesystem, (so let's reproduce the kernel infrastructure in > > >> userspace while leaving it the kernel too)... why do you need initramfs > > >> to be tmpfs? You're using it for half a second, then discarding it, > > >> what's the point of it being tmpfs? > > > > > > Unlike the kernel image which is signed by the distros, the initramfs > > > doesn't come signed, because it is built on the target system. Even > > > if the initramfs did come signed, it is beneficial to measure and > > > appraise the individual files in the initramfs. > > > > You can still shoot yourself in the foot with tmpfs. People mount a /run > > and a /tmp and then as a normal user you can go > > https://twitter.com/landley/status/959103235305951233 and maybe the > > default should be a little more clever there... > > > > I'll throw it on the todo heap. :) > > > > >> Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > > >> is configured in, even when you're then going to overmount it with > > >> something else like you're doing, let's just _remove_ the test. If it > > >> can be tmpfs, have it be tmpfs. > > > > > > Very much appreciated! > > > > Not yet tested, but something like the attached? (Sorry for the > > half-finished doc changes in there, I'm at work and have a 5 minute > > break. I can test properly this evening if you don't get to it...) > > Yes, rootfs is being mounted as tmpfs. I don't think you can unconditionally replace ramfs with initramfs by default. Their behavior is different in some cases (e.g. pivot_root vs switch_root) and it can break many systems that expect ramfs by default.
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
Quoting Mimi Zohar (2018-02-01 13:51:52) > On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: > > On 02/01/2018 09:55 AM, Mimi Zohar wrote: > > > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > > > > >>> With your patch and specifying "root=tmpfs", dracut is complaining: > > >>> > > >>> dracut: FATAL: Don't know how to handle 'root=tmpfs' > > >>> dracut: refusing to continue > > >> > > >> [googles]... I do not understand why this package exists. > > >> > > >> If you're switching to another root filesystem, using a tool that > > >> wikipedia[citation needed] says has no purpose but to switch to another > > >> root filesystem, (so let's reproduce the kernel infrastructure in > > >> userspace while leaving it the kernel too)... why do you need initramfs > > >> to be tmpfs? You're using it for half a second, then discarding it, > > >> what's the point of it being tmpfs? > > > > > > Unlike the kernel image which is signed by the distros, the initramfs > > > doesn't come signed, because it is built on the target system. Even > > > if the initramfs did come signed, it is beneficial to measure and > > > appraise the individual files in the initramfs. > > > > You can still shoot yourself in the foot with tmpfs. People mount a /run > > and a /tmp and then as a normal user you can go > > https://twitter.com/landley/status/959103235305951233 and maybe the > > default should be a little more clever there... > > > > I'll throw it on the todo heap. :) > > > > >> Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > > >> is configured in, even when you're then going to overmount it with > > >> something else like you're doing, let's just _remove_ the test. If it > > >> can be tmpfs, have it be tmpfs. > > > > > > Very much appreciated! > > > > Not yet tested, but something like the attached? (Sorry for the > > half-finished doc changes in there, I'm at work and have a 5 minute > > break. I can test properly this evening if you don't get to it...) > > Yes, rootfs is being mounted as tmpfs. I don't think you can unconditionally replace ramfs with initramfs by default. Their behavior is different in some cases (e.g. pivot_root vs switch_root) and it can break many systems that expect ramfs by default.
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: > On 02/01/2018 09:55 AM, Mimi Zohar wrote: > > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > > >>> With your patch and specifying "root=tmpfs", dracut is complaining: > >>> > >>> dracut: FATAL: Don't know how to handle 'root=tmpfs' > >>> dracut: refusing to continue > >> > >> [googles]... I do not understand why this package exists. > >> > >> If you're switching to another root filesystem, using a tool that > >> wikipedia[citation needed] says has no purpose but to switch to another > >> root filesystem, (so let's reproduce the kernel infrastructure in > >> userspace while leaving it the kernel too)... why do you need initramfs > >> to be tmpfs? You're using it for half a second, then discarding it, > >> what's the point of it being tmpfs? > > > > Unlike the kernel image which is signed by the distros, the initramfs > > doesn't come signed, because it is built on the target system. Even > > if the initramfs did come signed, it is beneficial to measure and > > appraise the individual files in the initramfs. > > You can still shoot yourself in the foot with tmpfs. People mount a /run > and a /tmp and then as a normal user you can go > https://twitter.com/landley/status/959103235305951233 and maybe the > default should be a little more clever there... > > I'll throw it on the todo heap. :) > > >> Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > >> is configured in, even when you're then going to overmount it with > >> something else like you're doing, let's just _remove_ the test. If it > >> can be tmpfs, have it be tmpfs. > > > > Very much appreciated! > > Not yet tested, but something like the attached? (Sorry for the > half-finished doc changes in there, I'm at work and have a 5 minute > break. I can test properly this evening if you don't get to it...) Yes, rootfs is being mounted as tmpfs. Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Thu, 2018-02-01 at 11:09 -0600, Rob Landley wrote: > On 02/01/2018 09:55 AM, Mimi Zohar wrote: > > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > > >>> With your patch and specifying "root=tmpfs", dracut is complaining: > >>> > >>> dracut: FATAL: Don't know how to handle 'root=tmpfs' > >>> dracut: refusing to continue > >> > >> [googles]... I do not understand why this package exists. > >> > >> If you're switching to another root filesystem, using a tool that > >> wikipedia[citation needed] says has no purpose but to switch to another > >> root filesystem, (so let's reproduce the kernel infrastructure in > >> userspace while leaving it the kernel too)... why do you need initramfs > >> to be tmpfs? You're using it for half a second, then discarding it, > >> what's the point of it being tmpfs? > > > > Unlike the kernel image which is signed by the distros, the initramfs > > doesn't come signed, because it is built on the target system. Even > > if the initramfs did come signed, it is beneficial to measure and > > appraise the individual files in the initramfs. > > You can still shoot yourself in the foot with tmpfs. People mount a /run > and a /tmp and then as a normal user you can go > https://twitter.com/landley/status/959103235305951233 and maybe the > default should be a little more clever there... > > I'll throw it on the todo heap. :) > > >> Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > >> is configured in, even when you're then going to overmount it with > >> something else like you're doing, let's just _remove_ the test. If it > >> can be tmpfs, have it be tmpfs. > > > > Very much appreciated! > > Not yet tested, but something like the attached? (Sorry for the > half-finished doc changes in there, I'm at work and have a 5 minute > break. I can test properly this evening if you don't get to it...) Yes, rootfs is being mounted as tmpfs. Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 02/01/2018 09:55 AM, Mimi Zohar wrote: > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > >>> With your patch and specifying "root=tmpfs", dracut is complaining: >>> >>> dracut: FATAL: Don't know how to handle 'root=tmpfs' >>> dracut: refusing to continue >> >> [googles]... I do not understand why this package exists. >> >> If you're switching to another root filesystem, using a tool that >> wikipedia[citation needed] says has no purpose but to switch to another >> root filesystem, (so let's reproduce the kernel infrastructure in >> userspace while leaving it the kernel too)... why do you need initramfs >> to be tmpfs? You're using it for half a second, then discarding it, >> what's the point of it being tmpfs? > > Unlike the kernel image which is signed by the distros, the initramfs > doesn't come signed, because it is built on the target system. Even > if the initramfs did come signed, it is beneficial to measure and > appraise the individual files in the initramfs. You can still shoot yourself in the foot with tmpfs. People mount a /run and a /tmp and then as a normal user you can go https://twitter.com/landley/status/959103235305951233 and maybe the default should be a little more clever there... I'll throw it on the todo heap. :) >> Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs >> is configured in, even when you're then going to overmount it with >> something else like you're doing, let's just _remove_ the test. If it >> can be tmpfs, have it be tmpfs. > > Very much appreciated! Not yet tested, but something like the attached? (Sorry for the half-finished doc changes in there, I'm at work and have a 5 minute break. I can test properly this evening if you don't get to it...) Rob diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b98048b..a5b44b2 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3771,8 +3771,14 @@ debug-uart get routed to the D+ and D- pins of the usb port and the regular usb controller gets disabled. - root= [KNL] Root filesystem - See name_to_dev_t comment in init/do_mounts.c. + root= [KNL] Fallback root filesystem when not using initramfs + If initramfs contains an /init file to run as PID 1 the + kernel ignores this setting. When initramfs doesn't have + /init (or whatever rdinit= points to) the kernel calls + prepare_namespace() in init/do_mounts.c to mount another + filesystem over / and chroot into it, then looks for + /sbin/init in there. (And /etc/init, /bin/init, and + /bin/sh for historical reasons.) rootdelay= [KNL] Delay (in seconds) to pause before attempting to mount the root filesystem diff --git a/Documentation/filesystems/ramfs-rootfs-initramfs.txt b/Documentation/filesystems/ramfs-rootfs-initramfs.txt index b176928..f3c57ba 100644 --- a/Documentation/filesystems/ramfs-rootfs-initramfs.txt +++ b/Documentation/filesystems/ramfs-rootfs-initramfs.txt @@ -67,6 +67,10 @@ A ramfs derivative called tmpfs was created to add size limits, and the ability to write the data to swap space. Normal users can be allowed write access to tmpfs mounts. See Documentation/filesystems/tmpfs.txt for more information. +The kernel uses tmpfs for ramfs when CONFIG_TMPFS=y and no "root=" is +specified in the kernel command line. If you can't stop yourself from +specifying root= you can also use "root=tmpfs". + What is rootfs? --- @@ -236,22 +240,10 @@ An initramfs archive is a complete self-contained root filesystem for Linux. If you don't already understand what shared libraries, devices, and paths you need to get a minimal root filesystem up and running, here are some references: -http://www.tldp.org/HOWTO/Bootdisk-HOWTO/ -http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html -http://www.linuxfromscratch.org/lfs/view/stable/ - -The "klibc" package (http://www.kernel.org/pub/linux/libs/klibc) is -designed to be a tiny C library to statically link early userspace -code against, along with some related utilities. It is BSD licensed. -I use uClibc (http://www.uclibc.org) and busybox (http://www.busybox.net) -myself. These are LGPL and GPL, respectively. (A self-contained initramfs -package is planned for the busybox 1.3 release.) - -In theory you could use glibc, but that's not well suited for small embedded -uses like this. (A "hello world" program statically linked against glibc is -over 400k. With uClibc it's 7k. Also note that glibc dlopens libnss to do -name lookups, even when otherwise statically linked.) + http://www.tldp.org/HOWTO/Bootdisk-HOWTO/ + http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html + http://www.linuxfromscratch.org/lfs/view/stable/ A good first step is to get initramfs to run a statically linked "hello world" program as init, and test it under an emulator like qemu (www.qemu.org) or @@ -264,11
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 02/01/2018 09:55 AM, Mimi Zohar wrote: > On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > >>> With your patch and specifying "root=tmpfs", dracut is complaining: >>> >>> dracut: FATAL: Don't know how to handle 'root=tmpfs' >>> dracut: refusing to continue >> >> [googles]... I do not understand why this package exists. >> >> If you're switching to another root filesystem, using a tool that >> wikipedia[citation needed] says has no purpose but to switch to another >> root filesystem, (so let's reproduce the kernel infrastructure in >> userspace while leaving it the kernel too)... why do you need initramfs >> to be tmpfs? You're using it for half a second, then discarding it, >> what's the point of it being tmpfs? > > Unlike the kernel image which is signed by the distros, the initramfs > doesn't come signed, because it is built on the target system. Even > if the initramfs did come signed, it is beneficial to measure and > appraise the individual files in the initramfs. You can still shoot yourself in the foot with tmpfs. People mount a /run and a /tmp and then as a normal user you can go https://twitter.com/landley/status/959103235305951233 and maybe the default should be a little more clever there... I'll throw it on the todo heap. :) >> Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs >> is configured in, even when you're then going to overmount it with >> something else like you're doing, let's just _remove_ the test. If it >> can be tmpfs, have it be tmpfs. > > Very much appreciated! Not yet tested, but something like the attached? (Sorry for the half-finished doc changes in there, I'm at work and have a 5 minute break. I can test properly this evening if you don't get to it...) Rob diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b98048b..a5b44b2 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3771,8 +3771,14 @@ debug-uart get routed to the D+ and D- pins of the usb port and the regular usb controller gets disabled. - root= [KNL] Root filesystem - See name_to_dev_t comment in init/do_mounts.c. + root= [KNL] Fallback root filesystem when not using initramfs + If initramfs contains an /init file to run as PID 1 the + kernel ignores this setting. When initramfs doesn't have + /init (or whatever rdinit= points to) the kernel calls + prepare_namespace() in init/do_mounts.c to mount another + filesystem over / and chroot into it, then looks for + /sbin/init in there. (And /etc/init, /bin/init, and + /bin/sh for historical reasons.) rootdelay= [KNL] Delay (in seconds) to pause before attempting to mount the root filesystem diff --git a/Documentation/filesystems/ramfs-rootfs-initramfs.txt b/Documentation/filesystems/ramfs-rootfs-initramfs.txt index b176928..f3c57ba 100644 --- a/Documentation/filesystems/ramfs-rootfs-initramfs.txt +++ b/Documentation/filesystems/ramfs-rootfs-initramfs.txt @@ -67,6 +67,10 @@ A ramfs derivative called tmpfs was created to add size limits, and the ability to write the data to swap space. Normal users can be allowed write access to tmpfs mounts. See Documentation/filesystems/tmpfs.txt for more information. +The kernel uses tmpfs for ramfs when CONFIG_TMPFS=y and no "root=" is +specified in the kernel command line. If you can't stop yourself from +specifying root= you can also use "root=tmpfs". + What is rootfs? --- @@ -236,22 +240,10 @@ An initramfs archive is a complete self-contained root filesystem for Linux. If you don't already understand what shared libraries, devices, and paths you need to get a minimal root filesystem up and running, here are some references: -http://www.tldp.org/HOWTO/Bootdisk-HOWTO/ -http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html -http://www.linuxfromscratch.org/lfs/view/stable/ - -The "klibc" package (http://www.kernel.org/pub/linux/libs/klibc) is -designed to be a tiny C library to statically link early userspace -code against, along with some related utilities. It is BSD licensed. -I use uClibc (http://www.uclibc.org) and busybox (http://www.busybox.net) -myself. These are LGPL and GPL, respectively. (A self-contained initramfs -package is planned for the busybox 1.3 release.) - -In theory you could use glibc, but that's not well suited for small embedded -uses like this. (A "hello world" program statically linked against glibc is -over 400k. With uClibc it's 7k. Also note that glibc dlopens libnss to do -name lookups, even when otherwise statically linked.) + http://www.tldp.org/HOWTO/Bootdisk-HOWTO/ + http://www.tldp.org/HOWTO/From-PowerUp-To-Bash-Prompt-HOWTO.html + http://www.linuxfromscratch.org/lfs/view/stable/ A good first step is to get initramfs to run a statically linked "hello world" program as init, and test it under an emulator like qemu (www.qemu.org) or @@ -264,11
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > With your patch and specifying "root=tmpfs", dracut is complaining: > > > > dracut: FATAL: Don't know how to handle 'root=tmpfs' > > dracut: refusing to continue > > [googles]... I do not understand why this package exists. > > If you're switching to another root filesystem, using a tool that > wikipedia[citation needed] says has no purpose but to switch to another > root filesystem, (so let's reproduce the kernel infrastructure in > userspace while leaving it the kernel too)... why do you need initramfs > to be tmpfs? You're using it for half a second, then discarding it, > what's the point of it being tmpfs? Unlike the kernel image which is signed by the distros, the initramfs doesn't come signed, because it is built on the target system. Even if the initramfs did come signed, it is beneficial to measure and appraise the individual files in the initramfs. > Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > is configured in, even when you're then going to overmount it with > something else like you're doing, let's just _remove_ the test. If it > can be tmpfs, have it be tmpfs. Very much appreciated! thanks, Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Thu, 2018-02-01 at 09:20 -0600, Rob Landley wrote: > > With your patch and specifying "root=tmpfs", dracut is complaining: > > > > dracut: FATAL: Don't know how to handle 'root=tmpfs' > > dracut: refusing to continue > > [googles]... I do not understand why this package exists. > > If you're switching to another root filesystem, using a tool that > wikipedia[citation needed] says has no purpose but to switch to another > root filesystem, (so let's reproduce the kernel infrastructure in > userspace while leaving it the kernel too)... why do you need initramfs > to be tmpfs? You're using it for half a second, then discarding it, > what's the point of it being tmpfs? Unlike the kernel image which is signed by the distros, the initramfs doesn't come signed, because it is built on the target system. Even if the initramfs did come signed, it is beneficial to measure and appraise the individual files in the initramfs. > Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs > is configured in, even when you're then going to overmount it with > something else like you're doing, let's just _remove_ the test. If it > can be tmpfs, have it be tmpfs. Very much appreciated! thanks, Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/31/2018 10:22 PM, Mimi Zohar wrote: > On Wed, 2018-01-31 at 21:03 -0500, Arvind Sankar wrote: >> On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: >>> On 01/31/2018 04:07 PM, Mimi Zohar wrote: On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I configured in tmpfs and am using rootfs but I want that >>> rootfs > to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > it?) I must be missing something. Which systems don't specify "root=" on the boot command line. >>> >>> Any system using initrd or initramfs? >>> >> >> Don't a lot of initramfs setups use root= to tell the initramfs which >> actual root file system to switch to after early boot? You mean the option that _isn't_ passed through as an environment variable (the way ROOT= would be) so you have to parse /proc/cmdline to to see if it was passed in? If you really, really, really, really, really want to double down on the "no, this is the button, it doesn't do what I thought but I will MAKE it work" obsession, sure. > With your patch and specifying "root=tmpfs", dracut is complaining: > > dracut: FATAL: Don't know how to handle 'root=tmpfs' > dracut: refusing to continue [googles]... I do not understand why this package exists. If you're switching to another root filesystem, using a tool that wikipedia[citation needed] says has no purpose but to switch to another root filesystem, (so let's reproduce the kernel infrastructure in userspace while leaving it the kernel too)... why do you need initramfs to be tmpfs? You're using it for half a second, then discarding it, what's the point of it being tmpfs? Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs is configured in, even when you're then going to overmount it with something else like you're doing, let's just _remove_ the test. If it can be tmpfs, have it be tmpfs. Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/31/2018 10:22 PM, Mimi Zohar wrote: > On Wed, 2018-01-31 at 21:03 -0500, Arvind Sankar wrote: >> On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: >>> On 01/31/2018 04:07 PM, Mimi Zohar wrote: On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I configured in tmpfs and am using rootfs but I want that >>> rootfs > to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > it?) I must be missing something. Which systems don't specify "root=" on the boot command line. >>> >>> Any system using initrd or initramfs? >>> >> >> Don't a lot of initramfs setups use root= to tell the initramfs which >> actual root file system to switch to after early boot? You mean the option that _isn't_ passed through as an environment variable (the way ROOT= would be) so you have to parse /proc/cmdline to to see if it was passed in? If you really, really, really, really, really want to double down on the "no, this is the button, it doesn't do what I thought but I will MAKE it work" obsession, sure. > With your patch and specifying "root=tmpfs", dracut is complaining: > > dracut: FATAL: Don't know how to handle 'root=tmpfs' > dracut: refusing to continue [googles]... I do not understand why this package exists. If you're switching to another root filesystem, using a tool that wikipedia[citation needed] says has no purpose but to switch to another root filesystem, (so let's reproduce the kernel infrastructure in userspace while leaving it the kernel too)... why do you need initramfs to be tmpfs? You're using it for half a second, then discarding it, what's the point of it being tmpfs? Sigh. If people are ok with having rootfs just be tmpfs whenever tmpfs is configured in, even when you're then going to overmount it with something else like you're doing, let's just _remove_ the test. If it can be tmpfs, have it be tmpfs. Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Wed, 2018-01-31 at 21:03 -0500, Arvind Sankar wrote: > On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: > > On 01/31/2018 04:07 PM, Mimi Zohar wrote: > > > On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I > > > configured in tmpfs and am using rootfs but I want that > > rootfs > > >> to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, > > >> does > > >> it?) > > > > > > I must be missing something. Which systems don't specify "root=" on > > > the boot command line. > > > > Any system using initrd or initramfs? > > > > Don't a lot of initramfs setups use root= to tell the initramfs which > actual root file system to switch to after early boot? With your patch and specifying "root=tmpfs", dracut is complaining: dracut: FATAL: Don't know how to handle 'root=tmpfs' dracut: refusing to continue Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Wed, 2018-01-31 at 21:03 -0500, Arvind Sankar wrote: > On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: > > On 01/31/2018 04:07 PM, Mimi Zohar wrote: > > > On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I > > > configured in tmpfs and am using rootfs but I want that > > rootfs > > >> to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, > > >> does > > >> it?) > > > > > > I must be missing something. Which systems don't specify "root=" on > > > the boot command line. > > > > Any system using initrd or initramfs? > > > > Don't a lot of initramfs setups use root= to tell the initramfs which > actual root file system to switch to after early boot? With your patch and specifying "root=tmpfs", dracut is complaining: dracut: FATAL: Don't know how to handle 'root=tmpfs' dracut: refusing to continue Mimi
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: > On 01/31/2018 04:07 PM, Mimi Zohar wrote: > > On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I > > configured in tmpfs and am using rootfs but I want that > rootfs > >> to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > >> it?) > > > > I must be missing something. Which systems don't specify "root=" on > > the boot command line. > > Any system using initrd or initramfs? > Don't a lot of initramfs setups use root= to tell the initramfs which actual root file system to switch to after early boot?
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Wed, Jan 31, 2018 at 05:48:20PM -0600, Rob Landley wrote: > On 01/31/2018 04:07 PM, Mimi Zohar wrote: > > On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I > > configured in tmpfs and am using rootfs but I want that > rootfs > >> to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > >> it?) > > > > I must be missing something. Which systems don't specify "root=" on > > the boot command line. > > Any system using initrd or initramfs? > Don't a lot of initramfs setups use root= to tell the initramfs which actual root file system to switch to after early boot?
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/31/2018 04:07 PM, Mimi Zohar wrote: > On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I > configured in tmpfs and am using rootfs but I want that rootfs >> to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does >> it?) > > I must be missing something. Which systems don't specify "root=" on > the boot command line. Any system using initrd or initramfs? I have one at https://github.com/landley/mkroot that doesn't, for example. It's 600 lines of bash that builds simple Linux systems for a bunch of different architectures, each with a qemu wrapper to boot it to a shell prompt. And yes, it's using tmpfs for its initramfs, you can tell because "grep rootfs /proc/mounts" gives a size. That's also where I tested the patch I sent you. The root= option specifies the filesystem to mount OVER rootfs. I.E. it's the fallback root filesystem to mount when initramfs doesn't contain an executable /init that can become PID 1. If you DO have an /init in rootfs which the kernel manages to launch as PID 1, the kernel code never reaches the part that uses the root= argument. (Look for the call to prepare_namespace() in init/main.c, notice how it's only called if it can't _already_ find "/init".) That's why the test I added for initramfs vs initmpfs was "did they specify root=", because if they did it means they're telling the kernel what to mount over rootfs, so they're not staying in rootfs. That's what that argument MEANS. They're telling init/main.c what fallback filesystem to mount over rootfs _after_ failing to find /init in rootfs, therefore they're not keeping rootfs as their root filesystem for userspace. That said, a lot of people don't understand how this works, and they set root= to things like /dev/ram when using initrd because "we must set this knob to something, this is something, therefore we must set this knob to it". The fact setting root=/dev/random would have the exact same effect doesn't seem to bother them, they had Done It and It Worked, therefore it was the Right Thing To Do. QED. The patch last message was me going "alright, if people can't NOT twiddle the knob, even when doing it breaks things in an immediate and obvious way, and a big DO NOT TOUCH sign won't dissuade them, just give the knob an explicit 'off' setting that literally does the same thing as not touching it at all would". Your solution was to add a safety catch for the knob, which is edging into Rube Goldberg territory if you ask me. > If we want to include and restore xattrs, > there needs to be a way of using tmpfs. Yes, using tmpfs for initramfs is useful, that's why I submitted patches to hook it up back in 2013. (Personally I find "cat /dev/zero > /filename" _not_ hard locking your system instantly the most compelling feature. Although I believe what motivated my initmpfs patches way back when was somebody wanting to install an rpm into intramfs and the installer failing because ramfs hasn't got a size so "df" always returns zero.) > Mimi Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/31/2018 04:07 PM, Mimi Zohar wrote: > On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote:>> (The old "I > configured in tmpfs and am using rootfs but I want that rootfs >> to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does >> it?) > > I must be missing something. Which systems don't specify "root=" on > the boot command line. Any system using initrd or initramfs? I have one at https://github.com/landley/mkroot that doesn't, for example. It's 600 lines of bash that builds simple Linux systems for a bunch of different architectures, each with a qemu wrapper to boot it to a shell prompt. And yes, it's using tmpfs for its initramfs, you can tell because "grep rootfs /proc/mounts" gives a size. That's also where I tested the patch I sent you. The root= option specifies the filesystem to mount OVER rootfs. I.E. it's the fallback root filesystem to mount when initramfs doesn't contain an executable /init that can become PID 1. If you DO have an /init in rootfs which the kernel manages to launch as PID 1, the kernel code never reaches the part that uses the root= argument. (Look for the call to prepare_namespace() in init/main.c, notice how it's only called if it can't _already_ find "/init".) That's why the test I added for initramfs vs initmpfs was "did they specify root=", because if they did it means they're telling the kernel what to mount over rootfs, so they're not staying in rootfs. That's what that argument MEANS. They're telling init/main.c what fallback filesystem to mount over rootfs _after_ failing to find /init in rootfs, therefore they're not keeping rootfs as their root filesystem for userspace. That said, a lot of people don't understand how this works, and they set root= to things like /dev/ram when using initrd because "we must set this knob to something, this is something, therefore we must set this knob to it". The fact setting root=/dev/random would have the exact same effect doesn't seem to bother them, they had Done It and It Worked, therefore it was the Right Thing To Do. QED. The patch last message was me going "alright, if people can't NOT twiddle the knob, even when doing it breaks things in an immediate and obvious way, and a big DO NOT TOUCH sign won't dissuade them, just give the knob an explicit 'off' setting that literally does the same thing as not touching it at all would". Your solution was to add a safety catch for the knob, which is edging into Rube Goldberg territory if you ask me. > If we want to include and restore xattrs, > there needs to be a way of using tmpfs. Yes, using tmpfs for initramfs is useful, that's why I submitted patches to hook it up back in 2013. (Personally I find "cat /dev/zero > /filename" _not_ hard locking your system instantly the most compelling feature. Although I believe what motivated my initmpfs patches way back when was somebody wanting to install an rpm into intramfs and the installer failing because ramfs hasn't got a size so "df" always returns zero.) > Mimi Rob
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote: > On 01/30/2018 03:46 PM, Mimi Zohar wrote: > > Commit 16203a7a9422 ("initmpfs: make rootfs use tmpfs when CONFIG_TMPFS > > enabled") introduced using tmpfs as the rootfs filesystem. The use of > > tmpfs is limited to systems that do not specify "root=" on the boot > > command line. > > > > Without the check "!saved_root_name[0]", rootfs uses tmpfs. As there > > must be a valid reason for this check, this patch introduces a new boot > > command line option named "noramfs" to force rootfs to use tmpfs. > > > > Signed-off-by: Mimi Zohar> > How about just: > > diff --git a/init/do_mounts.c b/init/do_mounts.c > index 7cf4f6d..af66ede 100644 > --- a/init/do_mounts.c > +++ b/init/do_mounts.c > @@ -632,8 +632,8 @@ int __init init_rootfs(void) > if (err) > return err; > > - if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] && > - (!root_fs_names || strstr(root_fs_names, "tmpfs"))) { > + if (IS_ENABLED(CONFIG_TMPFS) && (!saved_root_name[0] || > + !strcmp(saved_root_name, "tmpfs"))) { > err = shmem_init(); > is_tmpfs = true; > } else { > > (Obviously-signed-off-by: Rob Landley ) > > I.E. if you somehow just can't stop yourself from specifying root= when > using rootfs, have "root=tmpfs" do what you want. I tried overloading "rootfstype=tmpfs", before posting this work around, but for some reason that just doesn't work. > > (The old "I configured in tmpfs and am using rootfs but I want that rootfs > to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > it?) I must be missing something. Which systems don't specify "root=" on the boot command line. If we want to include and restore xattrs, there needs to be a way of using tmpfs. Mimi > > > --- > > Documentation/admin-guide/kernel-parameters.txt | 2 ++ > > init/do_mounts.c| 15 +-- > > 2 files changed, 15 insertions(+), 2 deletions(-) > > I suppose I should do a documentation update too. Lemme send a proper one > after work... > > Rob > > P.S. While I'm at it, I've meant to wire up rootflags= so you can specify > a memory limit other than 50% forever, I should do that too. And resend > my "make DEVTMPFS_MOUNT apply to initramfs" patch (with the debian bug > workaround)... >
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On Wed, 2018-01-31 at 13:32 -0600, Rob Landley wrote: > On 01/30/2018 03:46 PM, Mimi Zohar wrote: > > Commit 16203a7a9422 ("initmpfs: make rootfs use tmpfs when CONFIG_TMPFS > > enabled") introduced using tmpfs as the rootfs filesystem. The use of > > tmpfs is limited to systems that do not specify "root=" on the boot > > command line. > > > > Without the check "!saved_root_name[0]", rootfs uses tmpfs. As there > > must be a valid reason for this check, this patch introduces a new boot > > command line option named "noramfs" to force rootfs to use tmpfs. > > > > Signed-off-by: Mimi Zohar > > How about just: > > diff --git a/init/do_mounts.c b/init/do_mounts.c > index 7cf4f6d..af66ede 100644 > --- a/init/do_mounts.c > +++ b/init/do_mounts.c > @@ -632,8 +632,8 @@ int __init init_rootfs(void) > if (err) > return err; > > - if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] && > - (!root_fs_names || strstr(root_fs_names, "tmpfs"))) { > + if (IS_ENABLED(CONFIG_TMPFS) && (!saved_root_name[0] || > + !strcmp(saved_root_name, "tmpfs"))) { > err = shmem_init(); > is_tmpfs = true; > } else { > > (Obviously-signed-off-by: Rob Landley ) > > I.E. if you somehow just can't stop yourself from specifying root= when > using rootfs, have "root=tmpfs" do what you want. I tried overloading "rootfstype=tmpfs", before posting this work around, but for some reason that just doesn't work. > > (The old "I configured in tmpfs and am using rootfs but I want that rootfs > to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does > it?) I must be missing something. Which systems don't specify "root=" on the boot command line. If we want to include and restore xattrs, there needs to be a way of using tmpfs. Mimi > > > --- > > Documentation/admin-guide/kernel-parameters.txt | 2 ++ > > init/do_mounts.c| 15 +-- > > 2 files changed, 15 insertions(+), 2 deletions(-) > > I suppose I should do a documentation update too. Lemme send a proper one > after work... > > Rob > > P.S. While I'm at it, I've meant to wire up rootflags= so you can specify > a memory limit other than 50% forever, I should do that too. And resend > my "make DEVTMPFS_MOUNT apply to initramfs" patch (with the debian bug > workaround)... >
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/30/2018 03:46 PM, Mimi Zohar wrote: > Commit 16203a7a9422 ("initmpfs: make rootfs use tmpfs when CONFIG_TMPFS > enabled") introduced using tmpfs as the rootfs filesystem. The use of > tmpfs is limited to systems that do not specify "root=" on the boot > command line. > > Without the check "!saved_root_name[0]", rootfs uses tmpfs. As there > must be a valid reason for this check, this patch introduces a new boot > command line option named "noramfs" to force rootfs to use tmpfs. > > Signed-off-by: Mimi ZoharHow about just: diff --git a/init/do_mounts.c b/init/do_mounts.c index 7cf4f6d..af66ede 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -632,8 +632,8 @@ int __init init_rootfs(void) if (err) return err; - if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] && - (!root_fs_names || strstr(root_fs_names, "tmpfs"))) { + if (IS_ENABLED(CONFIG_TMPFS) && (!saved_root_name[0] || + !strcmp(saved_root_name, "tmpfs"))) { err = shmem_init(); is_tmpfs = true; } else { (Obviously-signed-off-by: Rob Landley ) I.E. if you somehow just can't stop yourself from specifying root= when using rootfs, have "root=tmpfs" do what you want. (The old "I configured in tmpfs and am using rootfs but I want that rootfs to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does it?) > --- > Documentation/admin-guide/kernel-parameters.txt | 2 ++ > init/do_mounts.c| 15 +-- > 2 files changed, 15 insertions(+), 2 deletions(-) I suppose I should do a documentation update too. Lemme send a proper one after work... Rob P.S. While I'm at it, I've meant to wire up rootflags= so you can specify a memory limit other than 50% forever, I should do that too. And resend my "make DEVTMPFS_MOUNT apply to initramfs" patch (with the debian bug workaround)...
Re: [RFC PATCH] rootfs: force mounting rootfs as tmpfs
On 01/30/2018 03:46 PM, Mimi Zohar wrote: > Commit 16203a7a9422 ("initmpfs: make rootfs use tmpfs when CONFIG_TMPFS > enabled") introduced using tmpfs as the rootfs filesystem. The use of > tmpfs is limited to systems that do not specify "root=" on the boot > command line. > > Without the check "!saved_root_name[0]", rootfs uses tmpfs. As there > must be a valid reason for this check, this patch introduces a new boot > command line option named "noramfs" to force rootfs to use tmpfs. > > Signed-off-by: Mimi Zohar How about just: diff --git a/init/do_mounts.c b/init/do_mounts.c index 7cf4f6d..af66ede 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -632,8 +632,8 @@ int __init init_rootfs(void) if (err) return err; - if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] && - (!root_fs_names || strstr(root_fs_names, "tmpfs"))) { + if (IS_ENABLED(CONFIG_TMPFS) && (!saved_root_name[0] || + !strcmp(saved_root_name, "tmpfs"))) { err = shmem_init(); is_tmpfs = true; } else { (Obviously-signed-off-by: Rob Landley ) I.E. if you somehow just can't stop yourself from specifying root= when using rootfs, have "root=tmpfs" do what you want. (The old "I configured in tmpfs and am using rootfs but I want that rootfs to be ramfs, not tmpfs" code doesn't seem to be a real-world concern, does it?) > --- > Documentation/admin-guide/kernel-parameters.txt | 2 ++ > init/do_mounts.c| 15 +-- > 2 files changed, 15 insertions(+), 2 deletions(-) I suppose I should do a documentation update too. Lemme send a proper one after work... Rob P.S. While I'm at it, I've meant to wire up rootflags= so you can specify a memory limit other than 50% forever, I should do that too. And resend my "make DEVTMPFS_MOUNT apply to initramfs" patch (with the debian bug workaround)...