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Always run "dmesg" with sudo

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The dmesg command allows you to review the messages that are stored in the
ring buffer. Some Linux distributions have strict requirements for
dmesg, and you need to use sudo to use dmesg.
This commit is contained in:
Jim Huang 2021-09-25 02:09:13 +08:00
parent 11e40dc8ef
commit 707e193cbe
1 changed files with 6 additions and 7 deletions
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13
lkmpg.tex
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@ -412,7 +412,7 @@ It takes two parameters: a variable name and a free form string describing that
I would recommend playing around with this code:
\begin{verbatim}
$ sudo insmod hello-5.ko mystring="bebop" myintarray=-1
$ dmesg -t | tail -7
$ sudo dmesg -t | tail -7
myshort is a short integer: 1
myint is an integer: 420
mylong is a long integer: 9999
@ -422,11 +422,11 @@ myintarray[1] = 420
got 1 arguments for myintarray.
$ sudo rmmod hello-5
$ dmesg -t | tail -1
$ sudo dmesg -t | tail -1
Goodbye, world 5
$ sudo insmod hello-5.ko mystring="supercalifragilisticexpialidocious" myintarray=-1,-1
$ dmesg -t | tail -7
$ sudo dmesg -t | tail -7
myshort is a short integer: 1
myint is an integer: 420
mylong is a long integer: 9999
@ -436,7 +436,7 @@ myintarray[1] = -1
got 2 arguments for myintarray.
$ sudo rmmod hello-5
$ dmesg -t | tail -1
$ sudo dmesg -t | tail -1
Goodbye, world 5
$ sudo insmod hello-5.ko mylong=hello
@ -1684,12 +1684,11 @@ Here is a demonstration of how to calculate a sha256 hash within a kernel module
\samplec{examples/cryptosha256.c}
Make and install the module:
Install the module:
\begin{codebash}
make
sudo insmod cryptosha256.ko
dmesg
sudo dmesg
\end{codebash}
And you should see that the hash was calculated for the test string.