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Is dd if=/dev/urandom of=/dev/mem safe?
What do top's %MEM and VSZ mean?how to use dd to fill drive with 1'sWhat does `dd if=/dev/zero of=/dev/sda` doForce program to use /dev/urandomWhat does the letter 'u' mean in /dev/urandom?Is it OK to just copy /dev/random and /dev/urandom?What are the --use-urandom or --use-random options in LUKS used for?dd command writing to /dev/sdc changed size of diskHow to understand PBS output “mem” and “vmem” keep the same when the task is x-fold increased with mpirun -np x taskDifference between CONFIG_RANDOMIZE_BASE and CONFIG_RANDOMIZE_MEMORY in Linux kernel config
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What exactly does this do? I don't understand how you could access base memory with this...seems kinda weird. Is it safe?
dd if=/dev/urandom of=/dev/mem
ubuntu memory dd random
edited 8 hours ago
Kusalananda♦
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What exactly does this do? I don't understand how you could access base memory with this...seems kinda weird. Is it safe?
dd if=/dev/urandom of=/dev/mem
ubuntu memory dd random
edited 8 hours ago
Kusalananda♦
156k18 gold badges309 silver badges495 bronze badges
asked 9 hours ago
Coder14Coder14
92 bronze badges
New contributor
Coder14 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 |
What exactly does this do? I don't understand how you could access base memory with this...seems kinda weird. Is it safe?
dd if=/dev/urandom of=/dev/mem
ubuntu memory dd random
edited 8 hours ago
Kusalananda♦
156k18 gold badges309 silver badges495 bronze badges
asked 9 hours ago
Coder14Coder14
92 bronze badges
New contributor
Coder14 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
What exactly does this do? I don't understand how you could access base memory with this...seems kinda weird. Is it safe?
dd if=/dev/urandom of=/dev/mem
ubuntu memory dd random
ubuntu memory dd random
edited 8 hours ago
Kusalananda♦
156k18 gold badges309 silver badges495 bronze badges
asked 9 hours ago
Coder14Coder14
92 bronze badges
New contributor
Coder14 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 8 hours ago
Kusalananda♦
156k18 gold badges309 silver badges495 bronze badges
asked 9 hours ago
Coder14Coder14
92 bronze badges
New contributor
Coder14 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited 8 hours ago
Kusalananda♦
156k18 gold badges309 silver badges495 bronze badges
edited 8 hours ago
Kusalananda♦
156k18 gold badges309 silver badges495 bronze badges
edited 8 hours ago
Kusalananda♦
156k18 gold badges309 silver badges495 bronze badges
156k18 gold badges309 silver badges495 bronze badges
asked 9 hours ago
Coder14Coder14
92 bronze badges
New contributor
Coder14 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 9 hours ago
Coder14Coder14
92 bronze badges
asked 9 hours ago
Coder14Coder14
92 bronze badges
92 bronze badges
New contributor
Coder14 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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It is safe, if you have properly configured kernel ( safe because it won't work )
Per manual page mem(4):
/dev/mem is a character device file that is an image of the main
memory of the computer. It may be used, for example, to examine (and
even patch) the system.
So in theory, dd if=/dev/urandom of=/dev/mem should overwrite whole address space of the physical memory you have installed, and since kernel and other programs run from memory this should effectively crash the system. In practice, there's limit. From the same man page:
Since Linux 2.6.26, and depending on the architecture, the
CONFIG_STRICT_DEVMEM kernel configuration option limits the areas
which can be accessed through this file.
Trying this on virtual machine Ubuntu 18.04 , it returns an error dd: writing to '/dev/mem': Operation not permitted even with sudo and despite permissions for root crw-r-----. From Ubuntu Wiki:
/dev/mem protection
Some applications (Xorg) need direct access to the physical memory from user-space. The special file /dev/mem exists to provide this access. In the past, it was possible to view and change kernel memory from this file if an attacker had root access. The CONFIG_STRICT_DEVMEM kernel option was introduced to block non-device memory access (originally named CONFIG_NONPROMISC_DEVMEM).
So technically, no it is not safe (since it would crash the system) and if kernel option CONFIG_STRICT_DEVMEM is disabled that's a security hole, but from what I see so far the command wouldn't run if that option is enabled. According to cross-site duplicate, a reboot will fix any issues with it, but of course data in RAM at that time would be lost and not flushed to disk (if any had to be).
There is a suggested method on the duplicate linked earlier using busybox devmem so if you're determined to mess around with RAM, there may be a way after all.
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
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It is safe, if you have properly configured kernel ( safe because it won't work )
Per manual page mem(4):
/dev/mem is a character device file that is an image of the main
memory of the computer. It may be used, for example, to examine (and
even patch) the system.
So in theory, dd if=/dev/urandom of=/dev/mem should overwrite whole address space of the physical memory you have installed, and since kernel and other programs run from memory this should effectively crash the system. In practice, there's limit. From the same man page:
Since Linux 2.6.26, and depending on the architecture, the
CONFIG_STRICT_DEVMEM kernel configuration option limits the areas
which can be accessed through this file.
Trying this on virtual machine Ubuntu 18.04 , it returns an error dd: writing to '/dev/mem': Operation not permitted even with sudo and despite permissions for root crw-r-----. From Ubuntu Wiki:
/dev/mem protection
Some applications (Xorg) need direct access to the physical memory from user-space. The special file /dev/mem exists to provide this access. In the past, it was possible to view and change kernel memory from this file if an attacker had root access. The CONFIG_STRICT_DEVMEM kernel option was introduced to block non-device memory access (originally named CONFIG_NONPROMISC_DEVMEM).
So technically, no it is not safe (since it would crash the system) and if kernel option CONFIG_STRICT_DEVMEM is disabled that's a security hole, but from what I see so far the command wouldn't run if that option is enabled. According to cross-site duplicate, a reboot will fix any issues with it, but of course data in RAM at that time would be lost and not flushed to disk (if any had to be).
There is a suggested method on the duplicate linked earlier using busybox devmem so if you're determined to mess around with RAM, there may be a way after all.
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
add a comment |
It is safe, if you have properly configured kernel ( safe because it won't work )
Per manual page mem(4):
/dev/mem is a character device file that is an image of the main
memory of the computer. It may be used, for example, to examine (and
even patch) the system.
So in theory, dd if=/dev/urandom of=/dev/mem should overwrite whole address space of the physical memory you have installed, and since kernel and other programs run from memory this should effectively crash the system. In practice, there's limit. From the same man page:
Since Linux 2.6.26, and depending on the architecture, the
CONFIG_STRICT_DEVMEM kernel configuration option limits the areas
which can be accessed through this file.
Trying this on virtual machine Ubuntu 18.04 , it returns an error dd: writing to '/dev/mem': Operation not permitted even with sudo and despite permissions for root crw-r-----. From Ubuntu Wiki:
/dev/mem protection
Some applications (Xorg) need direct access to the physical memory from user-space. The special file /dev/mem exists to provide this access. In the past, it was possible to view and change kernel memory from this file if an attacker had root access. The CONFIG_STRICT_DEVMEM kernel option was introduced to block non-device memory access (originally named CONFIG_NONPROMISC_DEVMEM).
So technically, no it is not safe (since it would crash the system) and if kernel option CONFIG_STRICT_DEVMEM is disabled that's a security hole, but from what I see so far the command wouldn't run if that option is enabled. According to cross-site duplicate, a reboot will fix any issues with it, but of course data in RAM at that time would be lost and not flushed to disk (if any had to be).
There is a suggested method on the duplicate linked earlier using busybox devmem so if you're determined to mess around with RAM, there may be a way after all.
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
add a comment |
It is safe, if you have properly configured kernel ( safe because it won't work )
Per manual page mem(4):
/dev/mem is a character device file that is an image of the main
memory of the computer. It may be used, for example, to examine (and
even patch) the system.
So in theory, dd if=/dev/urandom of=/dev/mem should overwrite whole address space of the physical memory you have installed, and since kernel and other programs run from memory this should effectively crash the system. In practice, there's limit. From the same man page:
Since Linux 2.6.26, and depending on the architecture, the
CONFIG_STRICT_DEVMEM kernel configuration option limits the areas
which can be accessed through this file.
Trying this on virtual machine Ubuntu 18.04 , it returns an error dd: writing to '/dev/mem': Operation not permitted even with sudo and despite permissions for root crw-r-----. From Ubuntu Wiki:
/dev/mem protection
Some applications (Xorg) need direct access to the physical memory from user-space. The special file /dev/mem exists to provide this access. In the past, it was possible to view and change kernel memory from this file if an attacker had root access. The CONFIG_STRICT_DEVMEM kernel option was introduced to block non-device memory access (originally named CONFIG_NONPROMISC_DEVMEM).
So technically, no it is not safe (since it would crash the system) and if kernel option CONFIG_STRICT_DEVMEM is disabled that's a security hole, but from what I see so far the command wouldn't run if that option is enabled. According to cross-site duplicate, a reboot will fix any issues with it, but of course data in RAM at that time would be lost and not flushed to disk (if any had to be).
There is a suggested method on the duplicate linked earlier using busybox devmem so if you're determined to mess around with RAM, there may be a way after all.
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
It is safe, if you have properly configured kernel ( safe because it won't work )
Per manual page mem(4):
/dev/mem is a character device file that is an image of the main
memory of the computer. It may be used, for example, to examine (and
even patch) the system.
So in theory, dd if=/dev/urandom of=/dev/mem should overwrite whole address space of the physical memory you have installed, and since kernel and other programs run from memory this should effectively crash the system. In practice, there's limit. From the same man page:
Since Linux 2.6.26, and depending on the architecture, the
CONFIG_STRICT_DEVMEM kernel configuration option limits the areas
which can be accessed through this file.
Trying this on virtual machine Ubuntu 18.04 , it returns an error dd: writing to '/dev/mem': Operation not permitted even with sudo and despite permissions for root crw-r-----. From Ubuntu Wiki:
/dev/mem protection
Some applications (Xorg) need direct access to the physical memory from user-space. The special file /dev/mem exists to provide this access. In the past, it was possible to view and change kernel memory from this file if an attacker had root access. The CONFIG_STRICT_DEVMEM kernel option was introduced to block non-device memory access (originally named CONFIG_NONPROMISC_DEVMEM).
So technically, no it is not safe (since it would crash the system) and if kernel option CONFIG_STRICT_DEVMEM is disabled that's a security hole, but from what I see so far the command wouldn't run if that option is enabled. According to cross-site duplicate, a reboot will fix any issues with it, but of course data in RAM at that time would be lost and not flushed to disk (if any had to be).
There is a suggested method on the duplicate linked earlier using busybox devmem so if you're determined to mess around with RAM, there may be a way after all.
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
edited 8 hours ago
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
answered 8 hours ago
Sergiy KolodyazhnyySergiy Kolodyazhnyy
11k4 gold badges27 silver badges67 bronze badges
11k4 gold badges27 silver badges67 bronze badges
add a comment |
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Coder14 is a new contributor. Be nice, and check out our Code of Conduct.
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