Let's Encrypt on a Big-IP

lnxgeek... so it turns out dd can't skip more than 2 x ibs, ibs is 512 by default, and it bombs after 1025 bytes.

[blah@box ~]$ dd if=file.txt skip=1024 count=1 of=/tmp/tmp.AvKIkdviwr
1+0 records in
1+0 records out
512 bytes (512 B) copied, 0.000184931 s, 2.8 MB/s
[blah@box ~]$ dd if=file.txt skip=1025 count=1 of=/tmp/tmp.AvKIkdviwr
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000173094 s, 0.0 kB/s
[blah@box ~]$ dd if=file.txt skip=1026 count=1 of=/tmp/tmp.AvKIkdviwr
dd: ‘file.txt’: cannot skip to specified offset
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000192339 s, 0.0 kB/s
[blah@box ~]$ 

Basically looks like I need to explicitly set ibs to chunk size and skip N chunks when necessary,

[root@c01 ~] dd if=file.txt ibs=524288 skip=1 count=1 of=/tmp/tmp.AvKIkdviwr
0+1 records in
1+0 records out
512 bytes (512 B) copied, 0.000317561 s, 1.6 MB/s
[root@c01 ~]

I will double check dd behaviour and commit a fix to GitHub repo shortly.