Linux Development – Page 18

rpm –target: Unkown option

today when Im tring to refresh kernel 2.6.39 on my Fedora11 node, some small issue hit during make rpm progress.

[root@suse-pc linux-2.6.39]# make rpm
make clean
...
...
rpm  --target i386 -ta ../kernel-2.6.39.ZIP.tar.gz
--target: Unkown option

[root@suse-pc linux-2.6.39]# make rpm

make clean

...

rpm --target i386 -ta ../kernel-2.6.39.ZIP.tar.gz

--target: Unkown option

double check and file the problem,

in the file linux-2.6.39/scripts/package/Makefile, this scriptwill detect the current installation of rpmbuild. If failed it will choose rpm instead. That’s why I hit the problem.

 23
 24 # Do we have rpmbuild, otherwise fall back to the older rpm
 25 RPM := $(shell if [ -x "/usr/bin/rpmbuild" ]; 
                   then echo rpmbuild; 
 26                else echo rpm; fi)
 27

24 # Do we have rpmbuild, otherwise fall back to the older rpm

25 RPM := $(shell if [ -x "/usr/bin/rpmbuild" ];

then echo rpmbuild;

26 else echo rpm; fi)

fix:
just refresh the rpm-build package and continue,.

yum install rpm-build -y

1	yum install rpm-build -y

setjmp and longjmp

I’m reading <Expert C Programming>

this topic 6.8 is on setjmp/longjmp mechanism,
compared with throw/catch this setting obviously has an re-enter callback.

notes,
-zip

#include &lt;setjmp.h&gt;

jmp_buf buf;

banana(){
	printf("In banana()n");
	longjmp(buf,1);

	printf("You'll never see this line.n");

}

main(){

	if (setjmp(buf))
		printf("back into mainn");
	else{
		printf("first time running n");
		banana();
	}

}

#include <setjmp.h>

jmp_buf buf;

banana(){

printf("In banana()n");

longjmp(buf,1);

printf("You'll never see this line.n");

}

main(){

if (setjmp(buf))

printf("back into mainn");

else{

printf("first time running n");

banana();

}

SIGLOST not support on Linux

这两天正好在看TLPI，有一处问题，正好给Mark写了一封信，人家回答也比较nice，不过更多么。。还是靠google了

SIGLOST This signal name exists on Linux, but is unused.

基本上我这边的Linux相关代码，都没有使用这个值，甚至一些架构(如MIPS)连comments这样的待遇都么有。

72 #define SIGIO 29
73 #define SIGPOLL SIGIO
74 /*
75      #define SIGLOST 29
76 */
77 #define SIGPWR 30

72 #define SIGIO 29

73 #define SIGPOLL SIGIO

74 /*

75 #define SIGLOST 29

76 */

77 #define SIGPWR 30

只有在Linux.SPARC上才找到这个信号的定义

76 #define SIGWINCH 28
77 #define SIGLOST 29
78 #define SIGPWR SIGLOST
79 #define SIGUSR1 30

76 #define SIGWINCH 28

77 #define SIGLOST 29

78 #define SIGPWR SIGLOST

79 #define SIGUSR1 30

当然，Solaris 10也有找到

 #define SIGLOST 37      /* resource lost (eg, record-lock lost) */</em></em>

1	#define SIGLOST 37 /* resource lost (eg, record-lock lost) */</em></em>

觉得比较有趣，记一下，顺便记一下Linux下 man signal(7)的描述

BUGS
SIGIO and SIGLOST have the same value. The latter is commented out in the kernel source, but the build process of some software still thinks that signal 29 is SIGLOST.

SSHd Debugging mode

今天同事有一个cluster出了点小问题，nodes之间passwdless SSH配不成功。我上去试了一下也不行。重新generate key也没用。

后来才试着debug，google了一下发现ssh和sshd的debug mode,(或者可以通过man ssh/sshd来得到)

SERVER> /usr/sbin/sshd -d -e
CLIENT > ssh -v hostname

关于几个参数的意思，

man sshd>

     -d      Debug mode. The server sends verbose debug output to the system log, and does not put itself in the background. The server
             also will not fork and will only process one connection. This option is only intended for debugging for the server. Multiple
             -d options increase the debugging level. Maximum is 3.

-e When this option is specified, sshd will send the output to the standard error instead of the system log.

man ssh>
-v Verbose mode. Causes ssh to print debugging messages about its progress. This is helpful in debugging connection, authentica-
tion, and configuration problems. Multiple -v options increase the verbosity. The maximum is 3.

这边可以尝试ssh -vvv ， sshd -dd来处理，
然后发现在client端发出请求后被拒绝，在log里看到server端打出的信息，原来是人家$HOME目录权限问题，居然为了方便把$HOME权限设成了777…..实在太无语了….改成700后一切正常。

debug2: monitor_read: 3 used once, disabling now
debug2: monitor_read: 4 used once, disabling now
debug1: temporarily_use_uid: 94068/55536 (e=0/0)
debug1: trying public key file /scratch/crsusr/.ssh/authorized_keys
Authentication refused: bad ownership or modes for directory /scratch/crsusr
debug1: restore_uid: 0/0
debug1: temporarily_use_uid: 94068/55536 (e=0/0)
debug1: trying public key file /scratch/crsusr/.ssh/authorized_keys2
debug1: restore_uid: 0/0

VI hit `LINE TOO LONG`

on solaris hit vim LINE TOO LONG problem when trying to open a logfile. it dues to a very long SQL Line.

Solution>
1> use fold command to reformat the file.
2> use sed to re-write the lines all.
3> cp to a linux node….where the buffer is larger..