I’ve been frustrated with the number of instructions that involve deleting a partition and then creating a new partition with the same starting block. Totally unnecessary! 

Life has gotten a lot easier thanks to the growpart command. The best part is that with the right filesystem you don’t even need to unmount.  I suggest taking a backup or snapshot first in case something goes wrong.

You can test it first with –dry-run:

Once that is done, just run the command for your given filesystem to expand into the rest of the partition.

For btrfs:

The amount can be something like +50g or max. To resize the root partition to max simply type:

For ext4 it is:

For example:

For XFS:

for example:

I’m putting this here since I haven’t seen it mentioned elsewhere and it took me forever to figure out:

I was getting timeouts on two different NVME drives, 2 different motherboards and two different CPUs, until I extended the timeout and after that I was just getting stalls. The fix was to disable ASPM:

echo performance > /sys/module/pcie_aspm/parameters/policy

Or you can add “pcie_aspm=off” to your kernel command line.

This is an Apache config sanitizer, it checks to make sure there are no orphaned files in the Debian style sites-available/sites-enabled type setup and checks to make sure each virtual host has a valid DNS.

 

Something I’ve been wondering but have yet to see a good explanation for is if there is a difference between the way GCC handles const and static const.  Now in theory the compiler should handle them the same way but does it?  My web search didn’t really come up with much so I decided to test for myself.

A quick test using GCC 4.7.2:

const.c

#include <string.h>
#include <stdio.h>

void test()
{
        const char i[] = "not changed";
        char *j;
        printf("before %s\n", i);

        j = i;

        strcpy(j, "changed");
        printf("after i=%s\n", i);
}

int main()
{
        test();
        test();
}

staticconst.c

#include <string.h>
#include <stdio.h>

void test()
{
        static const char i[] = "not changed";
        char *j;
        printf("before %s\n", i);

        j = i;

        strcpy(j, "changed");
        printf("after i=%s\n", i);
}

int main()
{
        test();
        test();
}

How each turns out:

const.c

~$ gcc const.c -o const -g
const.c: In function ‘test’:
const.c:10:4: warning: assignment discards ‘const’ qualifier from pointer target type [enabled by default]
~$ ./const
before not changed
after i=changed
before not changed
after i=changed

Not only can I change the variable, but it resets it at each function call so this means it is reallocating the variable each time.

staticconst.c

~$ gcc staticconst.c -o staticconst -g
staticconst.c: In function ‘test’:
staticconst.c:10:4: warning: assignment discards ‘const’ qualifier from pointer target type [enabled by default]
./staticconst
before not changed
Segmentation fault (core dumped)

gdb shows the following:

Core was generated by `./staticconst’.
Program terminated with signal 11, Segmentation fault.
#0  0x0000000000400534 in test () at staticconst.c:12
12        strcpy(j, “changed”);

As you can see static const is stored somewhere actually read only and being static it is not being reallocated each time the function is called making this version more efficient.