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Does the Linux kernel need a file system to run?
2019 Community Moderator ElectionDoes Android really use the same kernel as Linux?How to configure Linux to cache file metadata in preference to contents?File system that never breaks (data loss acceptable)When do I need to specify add_efi_memmap as kernel argument in UEFI/EFI boot?What files does the Linux kernel access?Root file system vs partition's file systemWhat parts of the Linux kernel I do not need?Linux/Embedded Linux - Understanding the Kernel and additional BSP specific componentsHow do I run the Linux kernel?Why does the Linux kernel build system use incremental linking or ar T thin archives?
My opinion is yes, it does, because all useful exposure to the outside world (non-priviledged processor mode) would first require a process running in the outside world. That would require a file system, even a temporary, in-RAM, file system.
Another engineer disagrees with me, but I can't seem to prove this beyond all (unknown to me) cases.
Does the answer to this question depend on the definition of 'running'?
filesystems linux-kernel
asked 4 hours ago
Peter L.Peter L.
1213
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
My opinion is yes, it does, because all useful exposure to the outside world (non-priviledged processor mode) would first require a process running in the outside world. That would require a file system, even a temporary, in-RAM, file system.
Another engineer disagrees with me, but I can't seem to prove this beyond all (unknown to me) cases.
Does the answer to this question depend on the definition of 'running'?
filesystems linux-kernel
asked 4 hours ago
Peter L.Peter L.
1213
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
i think that a running kernel does not "require"useful exposure to the outside world
– jsotola
3 hours ago
3
Brings to mind the old halted Linux firewall (circa 2002)
– Jeff Schaller
1 hour ago
add a comment |
My opinion is yes, it does, because all useful exposure to the outside world (non-priviledged processor mode) would first require a process running in the outside world. That would require a file system, even a temporary, in-RAM, file system.
Another engineer disagrees with me, but I can't seem to prove this beyond all (unknown to me) cases.
Does the answer to this question depend on the definition of 'running'?
filesystems linux-kernel
asked 4 hours ago
Peter L.Peter L.
1213
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
My opinion is yes, it does, because all useful exposure to the outside world (non-priviledged processor mode) would first require a process running in the outside world. That would require a file system, even a temporary, in-RAM, file system.
Another engineer disagrees with me, but I can't seem to prove this beyond all (unknown to me) cases.
Does the answer to this question depend on the definition of 'running'?
filesystems linux-kernel
filesystems linux-kernel
asked 4 hours ago
Peter L.Peter L.
1213
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
Peter L.Peter L.
1213
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
Peter L.Peter L.
1213
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
Peter L.Peter L.
1213
asked 4 hours ago
Peter L.Peter L.
1213
1213
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Peter L. is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
i think that a running kernel does not "require"useful exposure to the outside world
– jsotola
3 hours ago
3
Brings to mind the old halted Linux firewall (circa 2002)
– Jeff Schaller
1 hour ago
add a comment |
i think that a running kernel does not "require"useful exposure to the outside world
– jsotola
3 hours ago
3
Brings to mind the old halted Linux firewall (circa 2002)
– Jeff Schaller
1 hour ago
i think that a running kernel does not "require"
useful exposure to the outside world– jsotola
3 hours ago
i think that a running kernel does not "require"
useful exposure to the outside world– jsotola
3 hours ago
3
3
Brings to mind the old halted Linux firewall (circa 2002)
– Jeff Schaller
1 hour ago
Brings to mind the old halted Linux firewall (circa 2002)
– Jeff Schaller
1 hour ago
add a comment |
2 Answers
2
active
oldest
votes
That's rather an odd question because you don't run the kernel like you run a program. The kernel is a platform to run programs on. Of course there is setup and shutdown code but it's not possible to run the kernel on its own. There must always be a main "init" process. And the kernel will panic if it's not there. If init tries to exit the kernel will also panic.
These days the init process is something like systemd. If not otherwise specified the kernel will try to run a program starting with /sbin/init. See the init Param here http://man7.org/linux/man-pages/man7/bootparam.7.html in an emergency you can boot Linux with init=/bin/bash . But notice how you always specify a file on the file system to run.
So the kernel will panic if it starts up an has no file system because without one there is no way to load init.
Some confusion may arise because of a chicken and egg situation where the kernel must load drivers to access it's file system. To get round this an initial ramdisk is loaded from an image on disk containing vital drivers and setup scripts. These are executed before the file system is loaded. But make no mistake the initial ramdisk is itself a file system.
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
Isn't there a condition where the kernel gives up trying to initialize hardware and load a known file system (not initrd passed into the kernel via init params), then drops into a very limited shell (without init=/bin/bash)? Also, since you bring up /bin/bash, would the kernel always have that minimal file system available, even if it was built with other .config options that could potentially eliminate this?
– Peter L.
2 hours ago
@PeterL. that limit shell is some shell from the initrd/initramfs/whatever that kernel booted with, IIRC.
– muru
41 mins ago
add a comment |
In Linux, every device is a file, so you have to have a filesystem to run it.
answered 3 hours ago
K7AAYK7AAY
744825
3
But of course the device drivers exist inside the kernel irrespective of whether or not a device file points to them.
– Philip Couling
2 hours ago
add a comment |
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2 Answers
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2 Answers
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That's rather an odd question because you don't run the kernel like you run a program. The kernel is a platform to run programs on. Of course there is setup and shutdown code but it's not possible to run the kernel on its own. There must always be a main "init" process. And the kernel will panic if it's not there. If init tries to exit the kernel will also panic.
These days the init process is something like systemd. If not otherwise specified the kernel will try to run a program starting with /sbin/init. See the init Param here http://man7.org/linux/man-pages/man7/bootparam.7.html in an emergency you can boot Linux with init=/bin/bash . But notice how you always specify a file on the file system to run.
So the kernel will panic if it starts up an has no file system because without one there is no way to load init.
Some confusion may arise because of a chicken and egg situation where the kernel must load drivers to access it's file system. To get round this an initial ramdisk is loaded from an image on disk containing vital drivers and setup scripts. These are executed before the file system is loaded. But make no mistake the initial ramdisk is itself a file system.
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
Isn't there a condition where the kernel gives up trying to initialize hardware and load a known file system (not initrd passed into the kernel via init params), then drops into a very limited shell (without init=/bin/bash)? Also, since you bring up /bin/bash, would the kernel always have that minimal file system available, even if it was built with other .config options that could potentially eliminate this?
– Peter L.
2 hours ago
@PeterL. that limit shell is some shell from the initrd/initramfs/whatever that kernel booted with, IIRC.
– muru
41 mins ago
add a comment |
That's rather an odd question because you don't run the kernel like you run a program. The kernel is a platform to run programs on. Of course there is setup and shutdown code but it's not possible to run the kernel on its own. There must always be a main "init" process. And the kernel will panic if it's not there. If init tries to exit the kernel will also panic.
These days the init process is something like systemd. If not otherwise specified the kernel will try to run a program starting with /sbin/init. See the init Param here http://man7.org/linux/man-pages/man7/bootparam.7.html in an emergency you can boot Linux with init=/bin/bash . But notice how you always specify a file on the file system to run.
So the kernel will panic if it starts up an has no file system because without one there is no way to load init.
Some confusion may arise because of a chicken and egg situation where the kernel must load drivers to access it's file system. To get round this an initial ramdisk is loaded from an image on disk containing vital drivers and setup scripts. These are executed before the file system is loaded. But make no mistake the initial ramdisk is itself a file system.
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
Isn't there a condition where the kernel gives up trying to initialize hardware and load a known file system (not initrd passed into the kernel via init params), then drops into a very limited shell (without init=/bin/bash)? Also, since you bring up /bin/bash, would the kernel always have that minimal file system available, even if it was built with other .config options that could potentially eliminate this?
– Peter L.
2 hours ago
@PeterL. that limit shell is some shell from the initrd/initramfs/whatever that kernel booted with, IIRC.
– muru
41 mins ago
add a comment |
That's rather an odd question because you don't run the kernel like you run a program. The kernel is a platform to run programs on. Of course there is setup and shutdown code but it's not possible to run the kernel on its own. There must always be a main "init" process. And the kernel will panic if it's not there. If init tries to exit the kernel will also panic.
These days the init process is something like systemd. If not otherwise specified the kernel will try to run a program starting with /sbin/init. See the init Param here http://man7.org/linux/man-pages/man7/bootparam.7.html in an emergency you can boot Linux with init=/bin/bash . But notice how you always specify a file on the file system to run.
So the kernel will panic if it starts up an has no file system because without one there is no way to load init.
Some confusion may arise because of a chicken and egg situation where the kernel must load drivers to access it's file system. To get round this an initial ramdisk is loaded from an image on disk containing vital drivers and setup scripts. These are executed before the file system is loaded. But make no mistake the initial ramdisk is itself a file system.
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
That's rather an odd question because you don't run the kernel like you run a program. The kernel is a platform to run programs on. Of course there is setup and shutdown code but it's not possible to run the kernel on its own. There must always be a main "init" process. And the kernel will panic if it's not there. If init tries to exit the kernel will also panic.
These days the init process is something like systemd. If not otherwise specified the kernel will try to run a program starting with /sbin/init. See the init Param here http://man7.org/linux/man-pages/man7/bootparam.7.html in an emergency you can boot Linux with init=/bin/bash . But notice how you always specify a file on the file system to run.
So the kernel will panic if it starts up an has no file system because without one there is no way to load init.
Some confusion may arise because of a chicken and egg situation where the kernel must load drivers to access it's file system. To get round this an initial ramdisk is loaded from an image on disk containing vital drivers and setup scripts. These are executed before the file system is loaded. But make no mistake the initial ramdisk is itself a file system.
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
edited 2 hours ago
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
answered 2 hours ago
Philip CoulingPhilip Couling
2,031920
2,031920
Isn't there a condition where the kernel gives up trying to initialize hardware and load a known file system (not initrd passed into the kernel via init params), then drops into a very limited shell (without init=/bin/bash)? Also, since you bring up /bin/bash, would the kernel always have that minimal file system available, even if it was built with other .config options that could potentially eliminate this?
– Peter L.
2 hours ago
@PeterL. that limit shell is some shell from the initrd/initramfs/whatever that kernel booted with, IIRC.
– muru
41 mins ago
add a comment |
Isn't there a condition where the kernel gives up trying to initialize hardware and load a known file system (not initrd passed into the kernel via init params), then drops into a very limited shell (without init=/bin/bash)? Also, since you bring up /bin/bash, would the kernel always have that minimal file system available, even if it was built with other .config options that could potentially eliminate this?
– Peter L.
2 hours ago
@PeterL. that limit shell is some shell from the initrd/initramfs/whatever that kernel booted with, IIRC.
– muru
41 mins ago
Isn't there a condition where the kernel gives up trying to initialize hardware and load a known file system (not initrd passed into the kernel via init params), then drops into a very limited shell (without init=/bin/bash)? Also, since you bring up /bin/bash, would the kernel always have that minimal file system available, even if it was built with other .config options that could potentially eliminate this?
– Peter L.
2 hours ago
Isn't there a condition where the kernel gives up trying to initialize hardware and load a known file system (not initrd passed into the kernel via init params), then drops into a very limited shell (without init=/bin/bash)? Also, since you bring up /bin/bash, would the kernel always have that minimal file system available, even if it was built with other .config options that could potentially eliminate this?
– Peter L.
2 hours ago
@PeterL. that limit shell is some shell from the initrd/initramfs/whatever that kernel booted with, IIRC.
– muru
41 mins ago
@PeterL. that limit shell is some shell from the initrd/initramfs/whatever that kernel booted with, IIRC.
– muru
41 mins ago
add a comment |
In Linux, every device is a file, so you have to have a filesystem to run it.
answered 3 hours ago
K7AAYK7AAY
744825
3
But of course the device drivers exist inside the kernel irrespective of whether or not a device file points to them.
– Philip Couling
2 hours ago
add a comment |
In Linux, every device is a file, so you have to have a filesystem to run it.
answered 3 hours ago
K7AAYK7AAY
744825
3
But of course the device drivers exist inside the kernel irrespective of whether or not a device file points to them.
– Philip Couling
2 hours ago
add a comment |
In Linux, every device is a file, so you have to have a filesystem to run it.
answered 3 hours ago
K7AAYK7AAY
744825
In Linux, every device is a file, so you have to have a filesystem to run it.
answered 3 hours ago
K7AAYK7AAY
744825
answered 3 hours ago
K7AAYK7AAY
744825
answered 3 hours ago
K7AAYK7AAY
744825
answered 3 hours ago
K7AAYK7AAY
744825
744825
3
But of course the device drivers exist inside the kernel irrespective of whether or not a device file points to them.
– Philip Couling
2 hours ago
add a comment |
3
But of course the device drivers exist inside the kernel irrespective of whether or not a device file points to them.
– Philip Couling
2 hours ago
3
3
But of course the device drivers exist inside the kernel irrespective of whether or not a device file points to them.
– Philip Couling
2 hours ago
But of course the device drivers exist inside the kernel irrespective of whether or not a device file points to them.
– Philip Couling
2 hours ago
add a comment |
Peter L. is a new contributor. Be nice, and check out our Code of Conduct.
Peter L. is a new contributor. Be nice, and check out our Code of Conduct.
Peter L. is a new contributor. Be nice, and check out our Code of Conduct.
Peter L. is a new contributor. Be nice, and check out our Code of Conduct.
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i think that a running kernel does not "require"
useful exposure to the outside world– jsotola
3 hours ago
3
Brings to mind the old halted Linux firewall (circa 2002)
– Jeff Schaller
1 hour ago