10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
Hi ! all I am just trying to check range in my datafile
pls tell me why its resulting wrong
admin@IEEE:~/Desktop$ cat test.txt
0 28.4
5 28.4
10 28.4
15 28.5
20 28.5
25 28.6
30 28.6
35 28.7
40 28.7
45 28.7
50 28.8
55 28.8
60 28.8
65 28.1... (2 Replies)
Discussion started by: Akshay Hegde
2 Replies
2. UNIX for Advanced & Expert Users
I am working on a simple login ID check shell script that should prompt for a user ID then check to see if this user is logged on. Trying to get the hang of this stuff so I am thinking of my own little projects.
#! /bin/sh
echo "please enter a user name"
read user
if user=$user
then... (3 Replies)
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]#PATH=/usr/bin:/etc:/bin:/boot/grub:/boot/grup/bin:
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4. Shell Programming and Scripting
when user select option 2 nothing happen.for testing purpose I put
echo command but is not executing .
basically when user prompt for option 2,I want to get list of database name from user separeted by space (TEST DEVL)
and put into the file seprated by new line
TEST
DEVL
after that stay on... (1 Reply)
Discussion started by: okreporthai
1 Replies
5. UNIX for Dummies Questions & Answers
here is my command in bash shell on Mac OS X tiger:
history | tr -d emacs
here is what I get:
hitory | grp "" | tr -d ""
hitory | grp "" | tr -d """"
hitory | grp "" | tr -d ''
hitory | grp "" | tr -d ''
hitory | grp "" | tr -d ''
hitory | grp "" | tr -d... (3 Replies)
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6. UNIX for Dummies Questions & Answers
I really just mess around in UNIX, for the most part, when I want to get something done. I can usually piece things together by searching for brief how-to's on Google, but the syntax errors in my following .sh file are really confusing me. I've got lots of programming experience in other places, so... (7 Replies)
Discussion started by: demonpants
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7. UNIX for Dummies Questions & Answers
Hello,
I have a simple script such as
-----------------------------
#! /bin/sh
YEAR=`date -u +%Y`;
MONTH=`date -u +%m`;
DAY=`date -u +%d`;
DATE=$MONTH$DAY$YEAR
LOGFILES=auditTrail-$DATE
LOGMATCH=$LOGFILES\*
ARGUM=''
# find all files and write them to a file
find . -name... (7 Replies)
Discussion started by: arushunter
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8. Shell Programming and Scripting
Does anyone see anything wrong with this.
#getInfraFiles()
#{
# cd Infra/$DAY
# rm *
# /usr/bin/ftp -i -n $LINE << cmd
# user "$USER" "$PASSWD"
# cd $INFRAPATH
# binary
# mget *
# bye
#}
besides that its commented out (4 Replies)
Discussion started by: rcunn87
4 Replies
9. UNIX for Dummies Questions & Answers
#!/usr/bin/csh
#
DAY=`date +%y%m%d`
H=`date +%H`
M=`date +%M`
mailx -s "$H-Myfile" email@email.com</home/mydir/myfile
Thanks! (4 Replies)
Discussion started by: bobo
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10. UNIX for Advanced & Expert Users
When I execute following shell script I am getting the following error
syntax error at line 50 : `<<' unmatched
What am I doing wrong :confused:
Script begins here
----------------
MPAN_FILE=$1
exec 3<$MPAN_FILE ... (2 Replies)
Discussion started by: guptan
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CGROUP_NAMESPACES(7) Linux Programmer's Manual CGROUP_NAMESPACES(7)
NAME
cgroup_namespaces - overview of Linux cgroup namespaces
DESCRIPTION
For an overview of namespaces, see namespaces(7).
Cgroup namespaces virtualize the view of a process's cgroups (see cgroups(7)) as seen via /proc/[pid]/cgroup and /proc/[pid]/mountinfo.
Each cgroup namespace has its own set of cgroup root directories. These root directories are the base points for the relative locations
displayed in the corresponding records in the /proc/[pid]/cgroup file. When a process creates a new cgroup namespace using clone(2) or
unshare(2) with the CLONE_NEWCGROUP flag, it enters a new cgroup namespace in which its current cgroups directories become the cgroup root
directories of the new namespace. (This applies both for the cgroups version 1 hierarchies and the cgroups version 2 unified hierarchy.)
When viewing /proc/[pid]/cgroup, the pathname shown in the third field of each record will be relative to the reading process's root direc-
tory for the corresponding cgroup hierarchy. If the cgroup directory of the target process lies outside the root directory of the reading
process's cgroup namespace, then the pathname will show ../ entries for each ancestor level in the cgroup hierarchy.
The following shell session demonstrates the effect of creating a new cgroup namespace. First, (as superuser) we create a child cgroup in
the freezer hierarchy, and put the shell into that cgroup:
# mkdir -p /sys/fs/cgroup/freezer/sub
# echo $$ # Show PID of this shell
30655
# sh -c 'echo 30655 > /sys/fs/cgroup/freezer/sub/cgroup.procs'
# cat /proc/self/cgroup | grep freezer
7:freezer:/sub
Next, we use unshare(1) to create a process running a new shell in new cgroup and mount namespaces:
# unshare -Cm bash
We then inspect the /proc/[pid]/cgroup files of, respectively, the new shell process started by the unshare(1) command, a process that is
in the original cgroup namespace (init, with PID 1), and a process in a sibling cgroup (sub2):
$ cat /proc/self/cgroup | grep freezer
7:freezer:/
$ cat /proc/1/cgroup | grep freezer
7:freezer:/..
$ cat /proc/20124/cgroup | grep freezer
7:freezer:/../sub2
From the output of the first command, we see that the freezer cgroup membership of the new shell (which is in the same cgroup as the ini-
tial shell) is shown defined relative to the freezer cgroup root directory that was established when the new cgroup namespace was created.
(In absolute terms, the new shell is in the /sub freezer cgroup, and the root directory of the freezer cgroup hierarchy in the new cgroup
namespace is also /sub. Thus, the new shell's cgroup membership is displayed as '/'.)
However, when we look in /proc/self/mountinfo we see the following anomaly:
# cat /proc/self/mountinfo | grep freezer
155 145 0:32 /.. /sys/fs/cgroup/freezer ...
The fourth field of this line (/..) should show the directory in the cgroup filesystem which forms the root of this mount. Since by the
definition of cgroup namespaces, the process's current freezer cgroup directory became its root freezer cgroup directory, we should see '/'
in this field. The problem here is that we are seeing a mount entry for the cgroup filesystem corresponding to our initial shell process's
cgroup namespace (whose cgroup filesystem is indeed rooted in the parent directory of sub). We need to remount the freezer cgroup filesys-
tem inside this cgroup namespace, after which we see the expected results:
# mount --make-rslave / # Don't propagate mount events
# to other namespaces
# umount /sys/fs/cgroup/freezer
# mount -t cgroup -o freezer freezer /sys/fs/cgroup/freezer
# cat /proc/self/mountinfo | grep freezer
155 145 0:32 / /sys/fs/cgroup/freezer rw,relatime ...
Use of cgroup namespaces requires a kernel that is configured with the CONFIG_CGROUPS option.
CONFORMING TO
Namespaces are a Linux-specific feature.
NOTES
Among the purposes served by the virtualization provided by cgroup namespaces are the following:
* It prevents information leaks whereby cgroup directory paths outside of a container would otherwise be visible to processes in the con-
tainer. Such leakages could, for example, reveal information about the container framework to containerized applications.
* It eases tasks such as container migration. The virtualization provided by cgroup namespaces allows containers to be isolated from
knowledge of the pathnames of ancestor cgroups. Without such isolation, the full cgroup pathnames (displayed in /proc/self/cgroups)
would need to be replicated on the target system when migrating a container; those pathnames would also need to be unique, so that they
don't conflict with other pathnames on the target system.
* It allows better confinement of containerized processes, because it is possible to mount the container's cgroup filesystems such that the
container processes can't gain access to ancestor cgroup directories. Consider, for example, the following scenario:
o We have a cgroup directory, /cg/1, that is owned by user ID 9000.
o We have a process, X, also owned by user ID 9000, that is namespaced under the cgroup /cg/1/2 (i.e., X was placed in a new cgroup
namespace via clone(2) or unshare(2) with the CLONE_NEWCGROUP flag).
In the absence of cgroup namespacing, because the cgroup directory /cg/1 is owned (and writable) by UID 9000 and process X is also owned
by user ID 9000, then process X would be able to modify the contents of cgroups files (i.e., change cgroup settings) not only in /cg/1/2
but also in the ancestor cgroup directory /cg/1. Namespacing process X under the cgroup directory /cg/1/2, in combination with suitable
mount operations for the cgroup filesystem (as shown above), prevents it modifying files in /cg/1, since it cannot even see the contents
of that directory (or of further removed cgroup ancestor directories). Combined with correct enforcement of hierarchical limits, this
prevents process X from escaping the limits imposed by ancestor cgroups.
SEE ALSO
unshare(1), clone(2), setns(2), unshare(2), proc(5), cgroups(7), credentials(7), namespaces(7), user_namespaces(7)
COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the
latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 CGROUP_NAMESPACES(7)