Oct 12 2014
Group photo of class 9, MHSS
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Feb 25 2014
I happen to chance upon a good tutorial on the above topic. Here is the link for the tutorial
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Nov 17 2013
RAM is composed of chunks of memory called Pages. When programs execute, it takes fills up pages. Due to this sooner or later memory will run out. In order to free up the RAM, Pages can be swapped into hard drive and the freed up RAM can be used by the other program which needs CPU’s attention.
Swap space is not a must in Linux. So if you happen to have a system that does not have Swap space, then follow the below guide to create a swap file and use it.
Check whether a SWAP space is enabled
sudo swapon -s
if you do not have swap enabled in the system you should see the output as below
Filename Type Size Used Priority
Check the system for available space.
The recommended swap file size is twice the size of the RAM size. If your RAM
size is 512 MB, then the SWAP file size should be 1GB.
df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda 20642428 2367536 17226316 13% /
tmpfs 254432 0 254432 0% /lib/init/rw
udev 249612 60 249552 1% /dev
tmpfs 254432 4 254428 1% /dev/shm
Allocate space for swapfile
sudo fallocate -l 1GB /swapfile
Create Swap file
sudo mkswap /swapfile
the output will look like below
Setting up swapspace version 1, size = 8388608 KiB no label, UUID=103c4545-5fc5-47f3-a8b3-dfbdb64fd7eb
Turn on the SWAP file
sudo swapon /swapfile
You will then be able to see the new swap file when you view the swap summary.
swapon -s Filename Type Size Used Priority /swapfile file 8388608 0 -1
TO add this partition permanently, add it into /etc/fstab
sudo nano /etc/fstab
/swapfile none swap sw 0 0
save and close the fstab file.
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Nov 10 2013
A summary on how the different operator functions, in C++, have to be declared
(replace @ by the operator in each case):
Expression | Operator | Member function | Global function |
---|---|---|---|
@a | + – * & ! ~ ++ — | A::[email protected]() | [email protected](A) |
[email protected] | ++ — | A::[email protected](int) | [email protected](A,int) |
[email protected] | + – * / % ^ & | < > == !=
<= >= << >> && || , |
A::[email protected] (B) | [email protected](A,B) |
[email protected] | = += -= *= /= %= ^= &=
|= <<= >>= [] |
A::[email protected] (B) | – |
a(b, c…) | () | A::operator() (B, C…) | – |
a->x | -> | A::operator->() | – |
PS: This is for my reference that I copied from cplusplus.com.
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Oct 20 2013
If you want to override a named command in main.cf, normally you can specify in the master.cf as override option (-o) to the command.
There is one quirk here though. It cannot contain any white spaces. The manual page explain this clearly. However, it is silent when it comes to parameter values that contains whitespace. There are no examples as well.
The simple trick here is to replace white space with comma as well.
For example:
….. -o smtpd_client_restrictions=check_client_access,hash:/etc/postfix/access
Please see the comma after check_client_access.
But when you use this parameter in main.cf, it will be as below
smtpd_client_restrictions=check_client_access hash:/etc/postfix/access
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Oct 02 2013
If you have a Home NAS and if it supports SMB/CIFS shares, then follow the steps below to mount those shares in a Linux System.
Mount CIFS with the default local filesystem permissions:
# mkdir /mnt/mntpoint # mount -t cifs //server-name/share-name /mnt/mntpoint -o username=shareuser,password=sharepassword
For Example
# mount -t cifs //192.168.1.2/myfolder /mnt/mntpoint -o username=shareuser,password=sharepassword
Where,
For further details and options, please read linux man page for mount.cifs(8). Also, please note that only root user can mount the filesystems.
If you want a particular filesystem to mounted at boot time, then enter a static information about the filesystem you want to mount in /etc/fstab.
For example, in /etc/fstab you need to enter 6 feilds
“file system to be mounted” “mount point” “file type” “options” ” dump option” “file system check (fsck) value”
//192.168.1.2/myfolder /mnt/mntpoint cifs username=shareuser,password=sharepassword 0 0
if you want any user to mount this file system then do the following
//192.168.1.2/myfolder /mnt/mntpoint cifs username=shareuser,password=sharepassword,user 0 0
if you want to provide a resolvable hostname instead of IP address, then ensure that you have cifs-utils is installed. Otherwise you will fail to mount with error code -22 . If you do a dmesg after failure you will see the below message
cifs_mount failed w/return code = -22
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