lxcsu

   1 #!/usr/bin/python
   2
   3
   4 import setns
   5 import os
   6 import sys
   7
   8 from argparse import ArgumentParser
   9
  10 drop_capabilities='cap_sys_admin,cap_sys_boot,cap_sys_module'
  11
  12 def getarch(f):
  13     output = os.popen('readelf -h %s 2>&1'%f).readlines()
  14     classlines = [x for x in output if ('Class' in x.split(':')[0])]
  15     line = classlines[0]
  16     c = line.split(':')[1]
  17     if ('ELF64' in c):
  18         return 'x86_64'
  19     elif ('ELF32' in c):
  20         return 'i686'
  21     else:
  22         raise Exception('Could not determine architecture')
  23
  24 def umount(fs_dir):
  25     output = os.popen('/bin/umount %s 2>&1'%fs_dir).read()
  26     return ('device is busy' not in fs_dir)
  27
  28 def main ():
  29     parser = ArgumentParser()
  30     parser.add_argument("-n", "--nonet",
  31                         action="store_true", dest="netns", default=False,
  32                         help="Don't enter network namespace")
  33     parser.add_argument("-m", "--nomnt",
  34                         action="store_true", dest="mntns", default=False,
  35                         help="Don't enter mount namespace")
  36     parser.add_argument("-p", "--nopid",
  37                         action="store_true", dest="pidns", default=False,
  38                         help="Don't enter pid namespace")
  39     parser.add_argument("-r", "--root",
  40                         action="store_true", dest="root", default=False,
  41                         help="Enter as root: be careful")
  42     parser.add_argument ("slice",dest="slice_name",nargs=1)
  43
  44     options = parser.parse_args()
  45     slice_name=options.slice_name
  46
  47     try:
  48         cmd = 'grep %s /proc/*/cgroup | grep freezer'%slice_name
  49         output = os.popen(cmd).readlines()
  50     except:
  51         print "Error finding slice %s"%slice_name
  52         exit(1)
  53
  54     slice_spec = None
  55
  56     # xxx fixme xxx - provide a default as this is not always properly computed
  57     arch = 'x86_64'
  58
  59     for e in output:
  60         try:
  61             l = e.rstrip()
  62             path = l.split(':')[0]
  63             comp = l.rsplit(':')[-1]
  64             slice_name_check = comp.rsplit('/')[-1]
  65
  66             if (slice_name_check == slice_name):
  67                 slice_path = path
  68                 pid = slice_path.split('/')[2]
  69                 cmdline = open('/proc/%s/cmdline'%pid).read().rstrip('\n\x00')
  70                 if (cmdline == '/sbin/init'):
  71                     slice_spec = slice_path
  72                     arch = getarch('/proc/%s/exe'%pid)
  73                     break
  74         except:
  75             break
  76
  77     if (not slice_spec or not pid):
  78         print "Not started: %s"%slice_name
  79         exit(1)
  80
  81     # Enter cgroups
  82     try:
  83         for subsystem in ['cpuset','memory','blkio']:
  84             open('/sys/fs/cgroup/%s/libvirt/lxc/%s/tasks'%(subsystem,slice_name),'w').write(str(os.getpid()))
  85
  86     except:
  87         print "Error assigning resources: %s"%slice_name
  88         exit(1)
  89
  90     try:
  91         open('/sys/fs/cgroup/cpuacct/system/libvirtd.service/libvirt/lxc/%s/tasks'%slice_name,'w').write(str(os.getpid()))
  92     except:
  93         print "Error assigning cpuacct: %s" % slice_name
  94         exit(1)
  95
  96     # If the slice is frozen, then we'll get an EBUSY when trying to write to the task
  97     # list for the freezer cgroup. Since the user couldn't do anything anyway, it's best
  98     # in this case to error out the shell. (an alternative would be to un-freeze it,
  99     # add the task, and re-freeze it)
 100     try:
 101         f=open('/sys/fs/cgroup/freezer/libvirt/lxc/%s/tasks'%(slice_name),'w')
 102         f.write(str(os.getpid()))
 103         # note: we need to call f.close() explicitly, or we'll get an exception in
 104         # the object destructor, which will not be caught
 105         f.close()
 106     except:
 107         print "Error adding task to freezer cgroup. Slice is probably frozen: %s" % slice_name
 108         exit(1)
 109
 110     setns.chcontext('/proc/%s/ns/uts'%pid)
 111     setns.chcontext('/proc/%s/ns/ipc'%pid)
 112
 113     if (not options.netns):
 114         setns.chcontext('/proc/%s/ns/net'%pid)
 115
 116     if (not options.mntns):
 117         open('/proc/lxcsu','w').write(pid)
 118
 119     if (not options.pidns):
 120         open('/proc/pidsu','w').write(pid)
 121
 122     # cgroups is not yet LXC-safe, so we need to use the course grained access control
 123     # strategy of unmounting the filesystem
 124
 125     umount_result = True
 126     for subsystem in ['cpuset','cpu,cpuacct','memory','devices','freezer','net_cls','blkio','perf_event']:
 127         fs_path = '/sys/fs/cgroup/%s'%subsystem
 128         if (not umount(fs_path)):
 129             print "Error disabling cgroup access"
 130             exit(1)
 131
 132     if (not umount('/sys/fs/cgroup')):
 133         print "Error disabling cgroup access"
 134         exit(1)
 135
 136     pid = os.fork()
 137
 138     if (pid == 0):
 139         cap_arg = '--drop='+drop_capabilities
 140
 141         if (not options.root):
 142             exec_args = [arch,'/usr/sbin/capsh',cap_arg,'--','--login']+args[1:]
 143         else:
 144             exec_args = [arch,'/usr/sbin/capsh','--','--login']+args[1:]
 145
 146         os.environ['SHELL'] = '/bin/sh'
 147         os.execv('/usr/bin/setarch',exec_args)
 148     else:
 149         _,status = os.waitpid(pid,0)
 150         exit(os.WEXITSTATUS(status))
 151
 152 if __name__ == '__main__':
 153     main()