apt-get build-dep <package>
E: You must put some 'source' URIs in your sources.list
You have to enable deb-src in /etc/apt/sources.list.
Uncomment the deb-src line of the URLs which is enabled in deb line.
deb http://jp.archive.ubuntu.com/ubuntu xenial main restricted deb-src http://jp.archive.ubuntu.com/ubuntu xenial main restricted ...
yum-builddep <package>
After I have disabled password authentication on SSH, I want to attempt to connect with password authentication so that I confirm that password authentication is certainly disabled.
With -o option set PreferredAuthentications to password.
$ ssh -o PreferredAuthentications=password xxxx@example.com Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
If you see "Permission denied", it's OK.
set follow-fork-mode <mode>
mode should be parent(default) or child.
If you set mode to child, the new process is debugged after a fork.
show follow-fork-mode
displays the current mode.
Source: Forks - Debugging with GDB
Extends the functionality of other User-Agent addons, allowing them to modify the User-Agent for JavaScript code.
Source: User-Agent JS Fixer :: Add-ons for Firefox
This Firefox addon changes the Javascript navigator.userAgent.
All it does is to redefine the User-Agent for JavaScript code (navigator.userAgent) using the same string that was sent on the HTTP header.
Use it with addons which changes the HTTP header.
I use this addon with FireMobileSimulator.
In Mac OS X Terminal, you can clear scroll buffer by pressing Command+K.
Control+L (or clear command) can clear the screen and makes current prompt move to top of the screen, but scroll buffer is not cleared.
Core dump is not generated on Ubuntu(14.04 LTS) in some cases.
Sometimes it can be generated. It seems to depend on the program.
Like below ulimit is OK.
$ ulimit -c unlimited $ ulimit -a core file size (blocks, -c) unlimited data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 15739 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 15739 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited
I examined where the core dump is generated.
$ sudo sysctl -a | grep core_pattern kernel.core_pattern = |/usr/share/apport/apport %p %s %c %P
On Ubuntu(14.04 LTS) core_pattern uses apport by default.
In case core dump was successfully generated, core dump was generated in current directory.
In case core dump was not generated, an error occurred on apport.
/var/log/apport.log
ERROR: apport (pid 3480) Tue May 12 18:48:31 2015: called for pid 3479, signal 6, core limit 18446744073709551615
ERROR: apport (pid 3480) Tue May 12 18:48:31 2015: ignoring implausibly big core limit, treating as unlimited
ERROR: ERROR: apport (pid 3480) Tue May 12 18:48:31 2015: Unhandled exception:
Traceback (most recent call last):
File "/usr/share/apport/apport", line 357, in <module>
(info['ExecutablePath'], info['ProcCmdline']))
File "/usr/share/apport/apport", line 99, in error_log
apport.error('apport (pid %s) %s: %s', os.getpid(), time.asctime(), msg)
File "/usr/lib/python3/dist-packages/apport/__init__.py", line 44, in error
sys.stderr.write(msg % args)
UnicodeEncodeError: 'ascii' codec can't encode character '\ufffd' in position 143: ordinal not in range(128)
ERROR: apport (pid 3480) Tue May 12 18:48:31 2015: pid: 3480, uid: 0, gid: 0, euid: 0, egid: 0
ERROR: apport (pid 3480) Tue May 12 18:48:31 2015: environment: environ({})
Because an error occurred on apport, core dump was not generated.
This error seems to be Python's UnicodeEncodeError but I'm not sure, so I decided not to use apport in core_pattern.
# echo 'core.%e.%p' > /proc/sys/kernel/core_pattern
$ ulimit -c unlimited
$ cat segfault.c
#include <stdio.h>
int main(void)
{
char *s = "hello, world!";
*s = 'H';
return 0;
}
$ gcc -Wall -g -o segfault segfault.c
$ ./segfault
Segmentation fault (core dumped)
$ ls
core.segfault.3423 segfault segfault.c
Any configuration changes made using the echo command disappear when the system is restarted.
To make configuration changes take effect after the system is rebooted, edit /etc/sysctl.conf.
Source: E.4. Using the sysctl Command
/etc/sysctl.conf
kernel.core_pattern = core.%e.%p
But when the system is restarted, changes disappear and core_pattern uses apport.
When the system is restarted and apport starts, apport seems to overwrite configuration.
Source: 12.04 - How to permanently edit the core_pattern file? - Ask Ubuntu
To stop this behavior, disable apport and restart the system.
/etc/default/apport
# set this to 0 to disable apport, or to 1 to enable it # you can temporarily override this with # sudo service apport start force_start=1 #enabled=1 enabled=0
Recently I found that the free disk space of my Mac OS X (Yosemite) got very small, so I looked into why.
$ sudo du -sh /*
↓
$ sudo du -sh /private/*
↓
$ sudo du -sh /private/var/*
Finally I found that /private/var/tmp contained over 200GB files.
In /private/var/tmp there are many files whose name are such as cachegrind.out.50526.
It is said that these files are generated by Xdebug profiler.
Yes, I use Xdebug from MacPorts.
Xdebug is convenient because it shows stacktrace in error, enables stepping execution (but it needs Eclipse...), and so on.
Then I attempted to delete them with rm but an error occurred.
$ sudo rm cachegrind.out.* -bash: sudo: Argument list too long
Because the files were too many, shell expansion for "*" caused Argument list too long error.
Therefore I deleted them using find -exec.
$ cd /private/var/tmp
$ sudo find . -name 'cachegrind.out.*' -maxdepth 1 -exec rm {} \;
I got about 200GB free space.
See below for details about find -exec.
Delete or grep the results of find
If this goes on, files will be generated and they will fill up my disk again. So I decided to modify Xdebug setting so that Xdebug profiler will generate output files not in /private/var/tmp but in /tmp directory.
(I also set trace output directory to /tmp)
They will be deleted on rebooting.
/opt/local/etc/php53/php.ini
Add xdebug.profiler_output_dir and xdebug.trace_output_dir.
[xdebug] xdebug.profiler_enable=On xdebug.remote_enable=On xdebug.remote_host="localhost" xdebug.remote_port=9000 xdebug.remote_handler="dbgp" xdebug.idekey=ECLIPSE_DBGP xdebug.profiler_output_dir=/tmp/ ; where the profiler output will be written to xdebug.trace_output_dir=/tmp/ ; where the tracing files will be written to
Before installing SSL certificate and Intermediate CA certificate on Web server such as Apache, you may want to verify them.
You can do it using OpenSSL openssl command.
s_server implements a generic SSL/TLS server which accepts connections from remote clients speaking SSL/TLS.
openssl s_server -cert <path/to/certificate> -key <path/to/private key> -CAfile <path/to/Intermediate CA certificate>
Example:
$ openssl s_server -cert server.crt -key server.key -CAfile intermediate.crt Using default temp DH parameters Using default temp ECDH parameters ACCEPT
Connect to the server using openssl s_client and verify certificates.
s_client implements a generic SSL/TLS client which can establish a transparent connection to a remote server speaking SSL/TLS.
openssl s_client -connect localhost:4433 -CAfile <path/to/CA certificate>
Example of CA certificate:
Example:
$ openssl s_client -connect localhost:4433 -CAfile /opt/local/share/curl/curl-ca-bundle.crt
CONNECTED(00000003)
depth=3 (omitted)
verify return:1
depth=2 (omitted)
verify return:1
depth=1 (omitted)
verify return:1
depth=0 (omitted)
verify return:1
---
Certificate chain
0 s:(omitted)
i:(omitted)
1 s:(omitted)
i:(omitted)
2 s:(omitted)
i:(omitted)
3 s:(omitted)
i:(omitted)
---
Server certificate
-----BEGIN CERTIFICATE-----
(omitted)
-----END CERTIFICATE-----
subject=(omitted)
issuer=(omitted)
---
No client certificate CA names sent
---
SSL handshake has read 4744 bytes and written 443 bytes
---
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES256-GCM-SHA384
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: zlib compression
Expansion: zlib compression
SSL-Session:
Protocol : TLSv1.2
Cipher : ECDHE-RSA-AES256-GCM-SHA384
Session-ID: (omitted)
Session-ID-ctx:
Master-Key: (omitted)
Key-Arg : None
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket lifetime hint: 300 (seconds)
TLS session ticket:
(omitted)
Compression: 1 (zlib compression)
Start Time: 1421023132
Timeout : 300 (sec)
Verify return code: 0 (ok)
---
After you have installed certificates on the server, verify them with s_client like below.
-servername is needed for SNI (Server Name Indication).
$ openssl s_client -connect www.example.com:443 -servername www.example.com -showcerts -CAfile /opt/local/etc/openssl/cert.pem
$ openssl s_client -connect www.example.com:443 -servername www.example.com -showcerts
$ openssl s_client -connect www.example.com:443 -servername www.example.com -showcerts -CAfile /etc/ssl/certs/ca-certificates.crt
If you want to show expiring date of certificate,
$ echo | openssl s_client -connect www.example.com:443 -servername www.example.com -showcerts 2>/dev/null | openssl x509 -noout -dates
Install colordiff and configure Subversion's diff-cmd.
On Mac OS X, you can install colordiff using MacPorts.
$ sudo port install colordiff
On Debian or Ubuntu, you can install colordiff using apt.
$ sudo apt-get install colordiff
On other systems, you can download source tarball from http://www.colordiff.org/ and install colordiff.
~/.subversion/config
[helpers] diff-cmd = colordiff
$ svn diff | less -R
When I divide huge files such as log or CSV, I want them not to be divided in the middle of the line.
First, look into the number of lines in the file.
$ wc -l access_log 1197356 access_log
Divide the file by 100000 lines.
$ split -l 100000 access_log