Central file servers for Unix/Linux users
Central storage capacity is available for users in the NIKHEF network. Using this central storage has distinct advantages compared to storage on the local hard drive.
- Information on central file servers can be shared with other users.
- Central file servers are backed-up on a daily basis.
- Storage capacity is very large; up to a terabyte of data can be stored.
Home directory
Each account has a so called Home directory; in this directory user specific configuration files are stored. These files often start with a dot which makes them invisible in normal directory listings.
Email directories and user owned files are also stored in the Home directory.
Windows and Unix systems have separate Home directories. The path to your Unix Home directory is /user/loginname/...
Unix home directories can be accessed from a Windows environment through the Shares on file server ajax.nikhef.nl
Standard user file quota in Home directories is 400 Mb. You can check how much is used with the command quota -v
The numbers given are the numbers of 1024 byte disk blocks.
[newuser@eomer ~/$quota -vDisk quotas for user newuser (uid 123): Filesystem blocks quota limit grace files quota limit grace ajax:/export/ko/newuser 299009 395000 400000 6893 25000 30000
Each file and directory on a Unix system has a set of flags which controls who has read, write and execute rights. Likewise the Home directory; when a new Home directory is made, the flags are default set to owner allowed to read/write/execute and all others to read only. Listings of the directory content can be obtained via the ls command.
[newuser@eomer ~/]$ls -ld /user/newuserdrwxr-xr-x 70 newuser csg 6656 mrt 26 14:23 /user/newuser
The flags above show it to be a directory (d) on which the owner (newuser) has read (r), write (w) and execute (x) rights. The next group of three indicate rights for the group (csg) and the last group shows the rights for all other users on the system.
Changing these access rights can be done with the chmod command, using either an octal mask or a symbolic representation of the changes to be made.
[newuser@eomer ~/]$ chmod 700 /user/newuser
or
[newuser@eomer ~/]$ chmod go-rwx /user/newuser
Both commands will give the following result:
[newuser@eomer ~/]$ls -ld /user/newuserdrwx------ 70 newuser csg 6656 mrt 26 14:23 /user/newuser
Common project/group directories
Besides every user having a home directory, most users are members of groups or experiments which have storage capacity for common files on one of the central file servers. Use the groups command to see of which groups you are a member.
The amount of storage depends on whether the data is automatically backed-up or not. Capacity of non-backed-up directories is significantly greater than that of backed-up directories.
These directories can be accessed via the path /project/experiment, where project can be changed to group or global, since these all point to the same location. /project/atlas, /group/atlas and /global/atlas all point to the same directory.
Usually it isn't relevant to know on which server certain directories reside. When checking for available space, the output of the df command also shows the location on the server.
In the example below the file system /project/atlas is shown to reside on the file server pepijn and to be mounted on /export/data1/atlas.
[newuser@eomer ~]$df -h /project/atlasFilesystem Size Used Avail Use% Mounted onpepijn:/export/data1/atlas1.1T 180G 964G 16% /project/atlas
Automount
It is important to realize that directories on servers are only visible after they are referred to. This is also true for home directories. These are only mounted after log-in. The mechanism which takes care of this is called Automount.
An ls or cd command is enough to have the file system mounted. After a certain time of inactivity (approx. 5 minutes) the file system is automatically unmounted.
Since nothing is initially mounted, it is often unclear which directories are available.
The following command shows all directories under /project.
[newuser@eomer ~]$ ypcat -k auto.global | awk '{print $1 }'
Public directories
On the Unix/Linux desktops certain centrally installed applications are available. An example is the ROOT analysis application, published by CERN, which can be found in /public/cern/ROOT.
Applications for different platforms or operating system versions are installed in /public/platform/... where platform can be, for example, linux_redhat. Under this are separate directories for OS versions, such as i386_redhat7.
To make these applications easily accessible so called symbolic links are used. Thus, all centrally installed applications can be found under /usr/public. An ls in this directory will produce a list of all available programs. A number of these reside in /usr/public/bin; this path is by default installed in the $PATH variable of the log-in shell.
The directory of the web server, www.nikhef.nl, can be found in /public/www or via the symbolic link /www.